Abby Klosterbuer, BSc. PhD (cand.)

Abby Klosterbuer is currently a Ph.D. candidate at the Department of Food Science and Nutrition at the University of Minnesota, under the supervision of Dr. Joanne Slavin. Her Ph.D. work focuses on the effects of dietary fiber on satiety, glucose and inulin

release, gut hormones, and gut microflora. Abby is currently enrolled in her dietetic internship to become a Registered Dietitian.

SUMMER 2010 Vol 71 No 2 INSERT TO THE CANADIAN JOURNAL OF DIETETIC PRACTICE AND RESEARCH

Brought to you by the team of Registered Dietitians & Nutrition Professionals at

w w w . k e l l o g g s n u t r i t i o n . c a

Functionality of Different Fibres and Their Effects on Human Health

Joanne Slavin, PhD, RD.

Dr. Joanne Slavin is a professor in the Department of Food Science and Nutrition at the University of Minnesota. She has presented more than 250 invited scientific lectures around the world on topics including dietary fiber, carbohydrates, whole grains, and the role of diet in disease prevention. She is the author of more than 150 scientific publications and numerous book chapters and review articles. She is a Science Communicator for the Institute of Food Technologists and a member of numerous scientific societies, including the American Dietetic Association and the American

Society for Nutrition. She is a frequent source for the media on topics ranging from functional foods to sports nutrition. Dr. Slavin received B.S., M.S., and Ph.D. degrees in Nutritional Sciences from the University of Wisconsin-Madison and is a Registered Dietitian.

Dietary fibre is widely recognized as beneficial for overall human health, and high fibre intake is associated with reduced risk for a number of chronic conditions. The Institute of Medicine defines fibre in two parts: dietary fibre, which consists of nondigestible carbohydrate and lignin that are intrinsic and intact in plants, and functional fibre, which consists of isolated, nondigestible carbohydrates that have beneficial physiological effects in humans. Fibre was first included as a nutrient in the Dietary Reference Intakes (DRIs) in 2002, and the current recommendations are for individuals to consume between 25-38 grams of fibre per day.1 However, Canadians’ fibre intake falls dramatically short of the recommendations, with average intakes of both children and adults at about half of the Adequate intake levels.2

It is well recognized that different fibers exert different physiological effects. Traditionally, dietary fiber has been classified according to its solubility. In general, soluble fibers are considered to have benefits on serum lipids, while insoluble fibers are linked with laxation benefits. However, scientific evidence supporting that all soluble fibers lower cholesterol and all insoluble fibers increase stool weight is inconsistent. Many fiber sources, including oat bran and psyllium, are mostly soluble but still enlarge stool weight, however, wheat bran fibre is the only fibre to attain significant scientific agreement and be recognized as the gold standard for increasing stool weight by the Institute of Medicine.1

Increasingly, research indicates that additional properties, such as viscosity and fermentability, are more important characteristics in terms of physiological benefits. Viscous fibres are those that have gel-forming properties in the intestinal tract, and fermentable fibres are those that can

be metabolized by colonic bacteria. In general, soluble fibres are more completely fermented and have a higher viscosity than insoluble fibres. However, not all soluble fibres are viscous (e.g. partially hydrolyzed guar gum and acacia gum) and some insoluble fibres may be well fermented. Table 1 summarizes the classification of fibres based on these characteristics.3 It is clear that the term fibre encompasses a diverse range of substances with varying physiochemical properties and physiological effects.

Dietary Fibre Functional Fibre• Lignin • Resistant dextrins • Cellulose • Psyllium• B-glucans • Fructooligosaccharides• Hemicelluloses • Polydextrose • Pectins• Gums• Resistant Starch

Soluble Fibres Insoluble Fibres• B-glucans • Cellulose• Gums • Lignin• Wheat dextrin • Some pectins• Psyllium • Some hemicelluloses• Pectin Primary sources: wheat • Fructooligosaccharides bran, some vegetables• Inulin• Some hemicelluloses

Primary sources: oat products, legumes

Fermentable Fibre Non-fermentable Fibres• Wheat dextrin • Cellulose• Pectins • Lignin• B-glucans Primary sources: cereal fibres • Guar gum rich in cellulose (e.g. wheat bran)• Partially hydrolyzed guar gum• Inulin and oligofructose• Fructooligosaccharides

Primary sources: oats, barley, fruits and vegetables

Viscous Fibres Non-viscous Fibres• Pectins • Cellulose• B-glucans • Lignin• Some gums (e.g. guar gum) • Some hemicelluloses• Psyllium

Adapted from: Slavin et al. Journal of International Medical Research. 2009; 37:1-17

Table 1: Classification of fibres based on four characteristics

Average increase in fecal weight per gram fibre fed

Wheat 5.4 g/g fibre fed

Psyllium 4.0 g/g fibre fed

Cellulose 3.5 g/g fibre fed

Oats 3.4 g/g fibre fed

Corn 3.3 g/g fibre fed

Legumes 2.2 g/g fibre fed

Pectin 1.2 g/g fibre fed

Source: Cumming JH. 1993. CRC Handbook of Dietary Fibre

Table 2

Unlike in the United States, the following fibres can be used as ingredients in Canada, but according to labeling regulations, do not contribute to the total fibre value found in the Nutrition Facts table.

• Polydextrose

• Fructooligosaccharide

• Oligofructose

Effects of soluble fibre intake on serum LDL-cholesterol

Fibre Number Number Grams fibre/day Weighted net of Trials of Subjects (median) change (%)

Barley β -glucan 9 129 5 -11.1

Guar gum 4 79 15 -10.6

Oat β -glucan 13 457 6 -5.3

Pectin 5 71 15 -13.0

Psyllium 9 494 6 -5.5

Adapted from: Anderson JW, et al. Nutrition Reviews. 2009; 67(4):188-205

Table 3

HEALTH BENEFITS OF DIETARY FIBRE

Laxation and RegularityIt is well recognized that fibre is important for normal laxation. This is due primarily to the ability of fibre to increase stool weight. The increased weight is due to the physical presence of the fibre itself, water held by the fibre, and increased bacterial mass from fermentation.4 Larger and softer stools increase the ease of defecation and reduce transit time through the intestinal tract, which may help to prevent or relieve constipation. In general, cereal fibres are the most effective at increasing stool weight. Wheat bran is considered the “gold standard” when it comes to fecal bulking, since no other fibre or laxative has been shown to be as effective. Table 2 summarizes the ability of different fibres to increase stool weight.5

Not only insoluble fibres have an effect on laxation. Short Chain Fatty Acids, or SCFAs produced from fermentation of soluble fibres contribute to fecal bulk and increase the water content of feces. Inulin and oligofructose have been shown to increase fecal weight, as has polydextrose; however, significant scientific agreement has not been attained with these fibres.6,7 In addition, psyllium has been shown to have a range of effects, including increased stool frequency, increased stool weight, and improved stool consistency.8

Cholesterol Lowering

High fibre intake is associated with a lower prevalence of coronary heart disease.9 This may be due to the modifying effect certain fibres have on cardiovascular risk factors. Soluble, viscous fibres have been shown to significantly lower serum cholesterol levels. Table 3 summarizes the results of randomized, controlled trials examining the effect of soluble fibre on LDL cholesterol.10 The net changes in cholesterol (change with fibre treatment minus change with placebo) were weighted by number of subjects per trial.

The FDA has approved health claims for psyllium and β-glucan, two common sources of soluble fibre, in relation to reduced risk for coronary heart disease. The FDA concluded that 10.2 g/d of psyllium (providing 7 g of viscous fibre) or ≥3 g of β-glucan from oats should be consumed to achieve significant reductions in LDL cholesterol. While most studies are fairly short in duration, a few longer term studies with psyllium (6 months)

and guar gum (12 months) indicate that cholesterol reductions may be maintained with chronic consumption.11,12 The effects of these soluble fibres on serum lipids seem to be limited to LDL-cholesterol, and are not associated with changes in HDL-cholesterol or triglycerides. Health Canada is currently reviewing this claim for permissibility in Canada.

The mechanism for the cholesterol-lowering effects of soluble fibre is likely related to the ability of fibre to increase bile acid excretion. Bile acids are produced in the liver from cholesterol, and enter the small intestine, where they may be bound by fibre and eliminated in the feces. Increased loss requires the liver to use more cholesterol for bile acid synthesis, thus reducing the body’s cholesterol pool.13 In addition, short-chain fatty acid production from colonic fermentation of soluble fibres is thought to suppress hepatic cholesterol synthesis, which may contribute to this effect.14

Improved Glycemic and Insulinemic Response

Soluble fibre has also been shown to decrease glycemia and insulinemia. This may be related to the viscosity of the fibre. Viscous fibres, such as psyllium, β-glucan, and pectin, may form a gel in the small intestine, which acts to delay nutrient absorption, thus slowing delivery of glucose into the bloodstream and reducing the need for insulin. The ability of these fibres to lower postprandial glycemia and insulinemia has been established in numerous studies, but long-term effects are less well known. One study followed over 65,000 women for 6 years and found that dietary fibre intake was inversely associated with the development of type 2 diabetes.15

In addition, SCFAs produced from non-viscous, fermentable fibres may stimulate release of insulin from the pancreas and alter glycogen breakdown by the liver and so play a role in glucose metabolism.16 Consumption of inulin resulted in a significant decrease in fasting insulin concentrations, and intake of Fructooligosaccharides (FOS) caused a reduction in fasting glucose in patients with type 2 diabetes.17,18 In general, the effects of fibre on glucose and insulin levels are more pronounced in individuals with diabetes mellitus.

Prebiotic Effect and SCFA Production

Fermentable fibres may provide a number of health benefits by altering the composition of the intestinal flora. Prebiotics are non-digestible substances that provide a beneficial physiological effect to the host by selectively stimulating the favorable growth or activity of a limited number of indigenous bacteria.19 This generally refers to the ability of a fibre to increase the growth of bifidobacteria and lactobacilli, which are considered beneficial to human health. Benefits of prebiotics include improvement in gut barrier function and host immunity, reduction of potentially pathogenic bacteria subpopulations (e.g. clostridia), and enhanced SCFA production. Inulin, oligofructose, and FOS have been extensively studied as prebiotics, and have been shown to significantly increase fecal bifidobacteria at fairly low levels of consumption (5-8 grams per day).20 While these are the most well-studied prebiotic fibres, the ability to favorably alter the intestinal microflora has been demonstrated by a number of other fibre sources. Acacia gum was shown to produce a greater increase in bifidobacteria and lactobacilli than an equal dose of inulin, and resulted in fewer gastrointestinal side effects, such as gas and bloating.21 Polydextrose consumption resulted in a dose-dependent decrease in bacteroides, as well as an increase in lactobacilli and bifidobacteria.7 Wheat dextrin has also been shown to increase lactobacilli and reduce Clostridium perfringens.22

Fermentable fibres, such as pectin and β-glucans, that don’t meet the definition for prebiotics still provide health benefits via production of SCFAs. The three most abundant SCFAs are acetate, propionate, and butyrate, each of which exerts unique physiological effects. Of these, butyrate is considered the most beneficial in terms of colonic health. Butyrate is the preferred energy source for colonic epithelial cells, and promotes normal cell differentiation and proliferation.23 SCFAs also help regulate sodium and water absorption, and can enhance absorption of calcium and other minerals. In addition, SCFAs act to lower colonic pH, which can inhibit

growth of potential pathogens and promote the growth of beneficial bacteria such as bifidobacteria and lactobacilli. Different fibres vary in the amounts and ratio of SCFA produced, as well as in the rate of production. Fibres that are fermented quickly may lead to excessive gas production and bloating, so dose is an important consideration. Fermentation pattern may be related to the molecular weight, chain length, and structure of the fibre. Short chain molecules, such as FOS, are generally fermented more rapidly than larger, longer chain molecules such as acacia gum and partially hydrolyzed guar gum.

Immune Function and Inflammation

Some fibres may also play a role in improving immune function via production of SCFAs. In animal studies, addition of SCFAs to parenteral feeding caused an increase in T helper cells, macrophages, and neutrophils, and increased cytotoxic activity of natural killer cells.24 In humans, FOS consumption has been shown to increase T lymphocytes in adults and improve antibody response to a vaccine in infants.25,26 There is also some evidence of increased resistance to illness or infection with fibre intake. Oligofructose consumption was found to reduce febrile illness associated with diarrhea or respiratory events, and reduce antibiotic use in infants.27 Certain fibres, such as β-glucans, have been shown to interact with immune cells, and can therefore stimulate the immune system directly.28 Soluble, non-viscous fibre may also be potentially useful in alleviating symptoms of inflammatory conditions, such as irritable bowel syndrome (IBS). In particular, partially hydrolyzed guar gum has been shown to improve abdominal pain and bowel habits better than wheat bran and qualitative scores of epithelial injury and inflammation compared to control.29,30

Weight Regulation

Epidemiologic evidence suggests that increased intake of dietary fibre is protective against the development of obesity, and fibre consumption is inversely correlated with body weight and body fat. High fibre foods take longer to chew and tend to have a high volume and low energy density, which may help to promote satiety. Fibre also delays gastric emptying and nutrient absorption, which can extend feelings of fullness. Likewise, most studies with controlled energy intake indicate that dietary fibre increases feelings of satiety and reduces hunger following a meal.31 Viscous fibres, such as psyllium and guar gum, seem to be most successful at promoting satiety, but insoluble fibres, such as cellulose and wheat bran, have also been shown to be satiating.32 Other fibres, such as polydextrose, seem to have little effect on satiation.33

CONCLUSION:

Dietary fibres exhibit a diverse range of physiochemical properties and corresponding physiological effects. The role of fibre in health has extended far beyond improved laxation, and includes benefits on risk factors for cardiovascular disease, diabetes, weight management, immune function, and colonic health. However, it is clear that not all fibres are equal in terms of the types and extent of health benefits they provide. Characteristics such as solubility, fermentability, and viscosity are important determinants of the effect the fibre will have in the body. Due to the variability of fibre’s effects in the body, it is important to consume fibre from a variety of sources. In general, it is recommended to increase fibre consumption from whole foods, such as legumes, fruits, vegetables, and whole grains. Overall, increasing consumption of dietary fibre to recommended levels could play an important role in improving health of the general population.

References

1. Institute of Medicine of the National Academies. Dietary Reference Intakes: Energy, Carbohydrates, Fibre, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. Washington, D.C., USA: The National Academies Press; 2002.

2. Health Canada, Canadian Community Health Survey Cycle 2.2, Nutrition. (2004). Nutrient Intakes from Food. Provincial, Regional and National Summary Data Tables: Volume 1.

3. Slavin JL, Savarino V, Paredes-Diaz A, Fotopoulos G. A review of the role of soluble fibre in health with specific reference to wheat dextrin. J Int Med Res. 2009;37:1-17.

4. Kurasawa S, Haack VS, Marlett JA. Plant residue and bacteria as bases for increased stool weight accompanying consumption of higher dietary fibre diets. J Am Coll Nutr. 2000;19:426-433.

5. Cummings JH. The effect of dietary fibre on fecal weight and composition. In: Spiller GA, ed. CRC Handbook of Dietary Fibre in Human Nutrition. Boca Raton, FL: CRC Press; 1993:263-333.

6. Gibson GR, Beatty ER, Wang X, Cummings JH. Selective stimulation of bifidobacteria in the human colon by oligofructose and inulin. Gastroenterology. 1995;108:975-982.

7. Jie Z, Bang-Yao L, Ming-Jie X, et al. Studies on the effects of polydextrose intake on physiologic functions in chinese people. Am J Clin Nutr. 2000;72:1503-1509.

8. Ashraf W, Park F, Lof J, Quigley EM. Effects of psyllium therapy on stool characteristics, colon transit and anorectal function in chronic idiopathic constipation. Aliment Pharmacol Ther. 1995;9:639-647.

9. Pereira MA, Ludwig DS. Dietary fibre and body-weight regulation. observations and mechanisms. Pediatr Clin North Am. 2001;48:969-980.

10. Anderson JW, Baird P, Davis RH,Jr, et al. Health benefits of dietary fibre. Nutr Rev. 2009;67:188-205.

11. Anderson JW, Davidson MH, Blonde L, et al. Long-term cholesterol-lowering effects of psyllium as an adjunct to diet therapy in the treatment of hypercholesterolemia. Am J Clin Nutr. 2000;71:1433-1438.

12. Tuomilehto J, Silvasti M, Aro A, et al. Long term treatment of severe hypercholesterolaemia with guar gum. Atherosclerosis. 1988;72:157-162.

13. Trautwein EA, Kunath-Rau A, Erbersdobler HF. Increased fecal bile acid excretion and changes in the circulating bile acid pool are involved in the hypocholesterolemic and gallstone-preventive actions of psyllium in hamsters. J Nutr. 1999;129:896-902.

14. Wright RS, Anderson JW, Bridges SR. Propionate inhibits hepatocyte lipid synthesis. Proc Soc Exp Biol Med. 1990;195:26-29.

15. Salmeron J, Manson JE, Stampfer MJ, Colditz GA, Wing AL, Willett WC. Dietary fibre, glycemic load, and risk of non-insulin-dependent diabetes mellitus in women. JAMA. 1997;277:472-477.

16. Mineo H, Hashizume Y, Hanaki Y, et al. Chemical specificity of short-chain fatty acids in stimulating insulin and glucagon secretion in sheep. Am J Physiol. 1994;267:E234-41.

17. Brighenti F, Casiraghi MC, Canzi E, Ferrari A. Effect of consumption of a ready-to-eat breakfast cereal containing inulin on the intestinal milieu and blood lipids in healthy male volunteers. Eur J Clin Nutr. 1999;53:726-733.

18. Yamashita K, Kawai K, Itakura M. Effects of fructo-oligosaccharides on blood glucose and serum lipids in diabetic subjects. Nutr Research. 1984;4:961-966.

19. Gibson GR, Roberfroid MB. Dietary modulation of the human colonic microbiota: Introducing the concept of prebiotics. J Nutr. 1995;125:1401-1412.

20. Kolida S, Gibson GR. Prebiotic capacity of inulin-type fructans. J Nutr. 2007;137:2503S-2506S.

21. Calame W, Weseler AR, Viebke C, Flynn C, Siemensma AD. Gum arabic establishes prebiotic functionality in healthy human volunteers in a dose-dependent manner. Br J Nutr. 2008;100:1269-1275.

22. Pasman W, Wils D, Saniez MH, Kardinaal A. Long-term gastrointestinal tolerance of NUTRIOSE FB in healthy men. Eur J Clin Nutr. 2006;60:1024-1034.

23. Topping DL, Clifton PM. Short-chain fatty acids and human colonic function: Roles of resistant starch and nonstarch polysaccharides. Physiol Rev. 2001;81:1031-1064.

24. Pratt VC, Tappenden KA, McBurney MI, Field CJ. Short-chain fatty acid-supplemented total parenteral nutrition improves nonspecific immunity after intestinal resection in rats. JPEN J Parenter Enteral Nutr. 1996;20:264-271.

25. Guigoz Y, Rochat F, Perruisseau-Carrier G, Rochat I, Schiffrin E. Effects of oligosaccharides on the faecal flora and nonspecific immune system in elderly people. Nutrition Research. 2002;22:13.

26. Firmansyah A, Pramita G, Fassler C, Haschke F, Link-Amster H. Improved humoral immune response to measles vaccine in infants receiving infant cereal with fructo-oligosaccharides. Journal of Paediatric Gastroenterology and Nutrition. 2001;31:A521.

27. Saavedra JM, Tschernia A. Human studies with probiotics and prebiotics: Clinical implications. Br J Nutr. 2002;87 Suppl 2:S241-6.

28. Vetvicka V, Thornton BP, Ross GD. Soluble beta-glucan polysaccharide binding to the lectin site of neutrophil or natural killer cell complement receptor type 3 (CD11b/CD18) generates a primed state of the receptor capable of mediating cytotoxicity of iC3b-opsonized target cells. J Clin Invest. 1996;98:50-61.

29. Parisi GC, Zilli M, Miani MP, et al. High-fibre diet supplementation in patients with irritable bowel syndrome (IBS): A multicenter, randomized, open trial comparison between wheat bran diet and partially hydrolyzed guar gum (PHGG). Dig Dis Sci. 2002;47:1697-1704.

30. Garcia Peris P, Cuerda Compes C, Camblor Alvarez M. Dieta enteral polimerica estandar vs. dieta polimerica con fibra soluble en pacientes con colitis ulcerosa. Rev Esp Enf Digest. 1997;87:86.

31. Howarth NC, Saltzman E, Roberts SB. Dietary fibre and weight regulation. Nutr Rev. 2001;59:129-139.

32. Slavin J, Green H. Dietary fibre and satiety. Nutrition Bulletin. 2007;32:32-42. 33. Willis HJ, Eldridge AL, Beiseigel J, Thomas W, Slavin JL. Greater satiety response

with resistant starch and corn bran in human subjects. Nutr Res. 2009;29:100-105.

Fast Fibre Facts: Different Fibres, Different Impact on Health

1. Wheat Bran Fibre is the Best Fibre for Promoting Regularity In scientific studies on regularity, wheat bran is generally seen as

the “gold standard” against which other fibres are measured for efficacy.1 Look for products that have wheat bran or whole wheat as the first ingredient.

2. Soluble Fibres Lower Blood LDL Cholesterol Levels Psyllium fibre, β-glucan from oats and pectin rich fruits such as pears and apples are some

examples of soluble fibres that act like a sponge in the digestive system, soaking up cholesterol and helping to remove it from the body.

3. Prebiotic Fibres Stimulate the Growth of Healthy Bacteria in the Digestive System There are many healthy bacteria in the digestive tract that play important roles in helping

maintain health. By stimulating the growth of healthy bacteria, inulin and other prebiotic fibres have been shown to have a positive impact on immunity, calcium absorption and overall digestive health. Asparagus, leeks and Jerusalem artichokes naturally contain prebiotics. Prebiotics are also found in some dairy products like yogurt and cottage cheese and cereal products like the examples below that provide a source of prebiotic fibre.

In general, eating a healthy diet high in fibre has many proven health benefits ranging from promotion of a healthy digestive system to weight management to blood sugar management.

The following provide a few, quick Fast Facts on the role specific types of fibres play in health:

1. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein and Amino Acids. Institute of Medicine (U.S.). Panel on Macronutrients, Institute of Medicine (U.S.). Standing Committee on the Scientific Evaluation of Dietary Reference Intakes 2005

2. US Department of Health and Human Services. National Institute of Health. http://www.nhlbi.nih.gov/chd/Tipsheets/solfiber.htm

* © 2010, Trademark of Kellogg Company used under licence by Kellogg Canada Inc.

As an example, the first ingredient in All-Bran Buds* cereal is wheat bran.

Kellogg’s Guardian* cereal provides 4 g of soluble psyllium fibre per 1 cup (34 g) serving.

Fruits such as pears, apples and citrus fruits provide between 1 to 2 g of soluble fibre per 1 medium fruit.2

Fibre Plus Bars Kashi* GoLean Crunch!* cereal

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Abby Klosterbuer, BSc. PhD (cand.)

Abby Klosterbuer is currently a Ph.D. candidate at the Department of Food Science and Nutrition at the University of Minnesota, under the supervision of Dr. Joanne Slavin. Her Ph.D. work focuses on the effects of dietary fiber on satiety, glucose and inulin

release, gut hormones, and gut microflora. Abby is currently enrolled in her dietetic internship to become a Registered Dietitian.

SUMMER 2010 Vol 71 No 2 INSERT TO THE CANADIAN JOURNAL OF DIETETIC PRACTICE AND RESEARCH

Brought to you by the team of Registered Dietitians & Nutrition Professionals at

w w w . k e l l o g g s n u t r i t i o n . c a

Functionality of Different Fibres and Their Effects on Human Health

Joanne Slavin, PhD, RD.

Dr. Joanne Slavin is a professor in the Department of Food Science and Nutrition at the University of Minnesota. She has presented more than 250 invited scientific lectures around the world on topics including dietary fiber, carbohydrates, whole grains, and the role of diet in disease prevention. She is the author of more than 150 scientific publications and numerous book chapters and review articles. She is a Science Communicator for the Institute of Food Technologists and a member of numerous scientific societies, including the American Dietetic Association and the American

Society for Nutrition. She is a frequent source for the media on topics ranging from functional foods to sports nutrition. Dr. Slavin received B.S., M.S., and Ph.D. degrees in Nutritional Sciences from the University of Wisconsin-Madison and is a Registered Dietitian.

Dietary fibre is widely recognized as beneficial for overall human health, and high fibre intake is associated with reduced risk for a number of chronic conditions. The Institute of Medicine defines fibre in two parts: dietary fibre, which consists of nondigestible carbohydrate and lignin that are intrinsic and intact in plants, and functional fibre, which consists of isolated, nondigestible carbohydrates that have beneficial physiological effects in humans. Fibre was first included as a nutrient in the Dietary Reference Intakes (DRIs) in 2002, and the current recommendations are for individuals to consume between 25-38 grams of fibre per day.1 However, Canadians’ fibre intake falls dramatically short of the recommendations, with average intakes of both children and adults at about half of the Adequate intake levels.2

It is well recognized that different fibers exert different physiological effects. Traditionally, dietary fiber has been classified according to its solubility. In general, soluble fibers are considered to have benefits on serum lipids, while insoluble fibers are linked with laxation benefits. However, scientific evidence supporting that all soluble fibers lower cholesterol and all insoluble fibers increase stool weight is inconsistent. Many fiber sources, including oat bran and psyllium, are mostly soluble but still enlarge stool weight, however, wheat bran fibre is the only fibre to attain significant scientific agreement and be recognized as the gold standard for increasing stool weight by the Institute of Medicine.1

Increasingly, research indicates that additional properties, such as viscosity and fermentability, are more important characteristics in terms of physiological benefits. Viscous fibres are those that have gel-forming properties in the intestinal tract, and fermentable fibres are those that can

be metabolized by colonic bacteria. In general, soluble fibres are more completely fermented and have a higher viscosity than insoluble fibres. However, not all soluble fibres are viscous (e.g. partially hydrolyzed guar gum and acacia gum) and some insoluble fibres may be well fermented. Table 1 summarizes the classification of fibres based on these characteristics.3 It is clear that the term fibre encompasses a diverse range of substances with varying physiochemical properties and physiological effects.

Dietary Fibre Functional Fibre• Lignin • Resistant dextrins • Cellulose • Psyllium• B-glucans • Fructooligosaccharides• Hemicelluloses • Polydextrose • Pectins• Gums• Resistant Starch

Soluble Fibres Insoluble Fibres• B-glucans • Cellulose• Gums • Lignin• Wheat dextrin • Some pectins• Psyllium • Some hemicelluloses• Pectin Primary sources: wheat • Fructooligosaccharides bran, some vegetables• Inulin• Some hemicelluloses

Primary sources: oat products, legumes

Fermentable Fibre Non-fermentable Fibres• Wheat dextrin • Cellulose• Pectins • Lignin• B-glucans Primary sources: cereal fibres • Guar gum rich in cellulose (e.g. wheat bran)• Partially hydrolyzed guar gum• Inulin and oligofructose• Fructooligosaccharides

Primary sources: oats, barley, fruits and vegetables

Viscous Fibres Non-viscous Fibres• Pectins • Cellulose• B-glucans • Lignin• Some gums (e.g. guar gum) • Some hemicelluloses• Psyllium

Adapted from: Slavin et al. Journal of International Medical Research. 2009; 37:1-17

Table 1: Classification of fibres based on four characteristics

Average increase in fecal weight per gram fibre fed

Wheat 5.4 g/g fibre fed

Psyllium 4.0 g/g fibre fed

Cellulose 3.5 g/g fibre fed

Oats 3.4 g/g fibre fed

Corn 3.3 g/g fibre fed

Legumes 2.2 g/g fibre fed

Pectin 1.2 g/g fibre fed

Source: Cumming JH. 1993. CRC Handbook of Dietary Fibre

Table 2

Unlike in the United States, the following fibres can be used as ingredients in Canada, but according to labeling regulations, do not contribute to the total fibre value found in the Nutrition Facts table.

• Polydextrose

• Fructooligosaccharide

• Oligofructose

Effects of soluble fibre intake on serum LDL-cholesterol

Fibre Number Number Grams fibre/day Weighted net of Trials of Subjects (median) change (%)

Barley β -glucan 9 129 5 -11.1

Guar gum 4 79 15 -10.6

Oat β -glucan 13 457 6 -5.3

Pectin 5 71 15 -13.0

Psyllium 9 494 6 -5.5

Adapted from: Anderson JW, et al. Nutrition Reviews. 2009; 67(4):188-205

Table 3

HEALTH BENEFITS OF DIETARY FIBRE

Laxation and RegularityIt is well recognized that fibre is important for normal laxation. This is due primarily to the ability of fibre to increase stool weight. The increased weight is due to the physical presence of the fibre itself, water held by the fibre, and increased bacterial mass from fermentation.4 Larger and softer stools increase the ease of defecation and reduce transit time through the intestinal tract, which may help to prevent or relieve constipation. In general, cereal fibres are the most effective at increasing stool weight. Wheat bran is considered the “gold standard” when it comes to fecal bulking, since no other fibre or laxative has been shown to be as effective. Table 2 summarizes the ability of different fibres to increase stool weight.5

Not only insoluble fibres have an effect on laxation. Short Chain Fatty Acids, or SCFAs produced from fermentation of soluble fibres contribute to fecal bulk and increase the water content of feces. Inulin and oligofructose have been shown to increase fecal weight, as has polydextrose; however, significant scientific agreement has not been attained with these fibres.6,7 In addition, psyllium has been shown to have a range of effects, including increased stool frequency, increased stool weight, and improved stool consistency.8

Cholesterol Lowering

High fibre intake is associated with a lower prevalence of coronary heart disease.9 This may be due to the modifying effect certain fibres have on cardiovascular risk factors. Soluble, viscous fibres have been shown to significantly lower serum cholesterol levels. Table 3 summarizes the results of randomized, controlled trials examining the effect of soluble fibre on LDL cholesterol.10 The net changes in cholesterol (change with fibre treatment minus change with placebo) were weighted by number of subjects per trial.

The FDA has approved health claims for psyllium and β-glucan, two common sources of soluble fibre, in relation to reduced risk for coronary heart disease. The FDA concluded that 10.2 g/d of psyllium (providing 7 g of viscous fibre) or ≥3 g of β-glucan from oats should be consumed to achieve significant reductions in LDL cholesterol. While most studies are fairly short in duration, a few longer term studies with psyllium (6 months)

and guar gum (12 months) indicate that cholesterol reductions may be maintained with chronic consumption.11,12 The effects of these soluble fibres on serum lipids seem to be limited to LDL-cholesterol, and are not associated with changes in HDL-cholesterol or triglycerides. Health Canada is currently reviewing this claim for permissibility in Canada.

The mechanism for the cholesterol-lowering effects of soluble fibre is likely related to the ability of fibre to increase bile acid excretion. Bile acids are produced in the liver from cholesterol, and enter the small intestine, where they may be bound by fibre and eliminated in the feces. Increased loss requires the liver to use more cholesterol for bile acid synthesis, thus reducing the body’s cholesterol pool.13 In addition, short-chain fatty acid production from colonic fermentation of soluble fibres is thought to suppress hepatic cholesterol synthesis, which may contribute to this effect.14

Improved Glycemic and Insulinemic Response

Soluble fibre has also been shown to decrease glycemia and insulinemia. This may be related to the viscosity of the fibre. Viscous fibres, such as psyllium, β-glucan, and pectin, may form a gel in the small intestine, which acts to delay nutrient absorption, thus slowing delivery of glucose into the bloodstream and reducing the need for insulin. The ability of these fibres to lower postprandial glycemia and insulinemia has been established in numerous studies, but long-term effects are less well known. One study followed over 65,000 women for 6 years and found that dietary fibre intake was inversely associated with the development of type 2 diabetes.15

In addition, SCFAs produced from non-viscous, fermentable fibres may stimulate release of insulin from the pancreas and alter glycogen breakdown by the liver and so play a role in glucose metabolism.16 Consumption of inulin resulted in a significant decrease in fasting insulin concentrations, and intake of Fructooligosaccharides (FOS) caused a reduction in fasting glucose in patients with type 2 diabetes.17,18 In general, the effects of fibre on glucose and insulin levels are more pronounced in individuals with diabetes mellitus.

Prebiotic Effect and SCFA Production

Fermentable fibres may provide a number of health benefits by altering the composition of the intestinal flora. Prebiotics are non-digestible substances that provide a beneficial physiological effect to the host by selectively stimulating the favorable growth or activity of a limited number of indigenous bacteria.19 This generally refers to the ability of a fibre to increase the growth of bifidobacteria and lactobacilli, which are considered beneficial to human health. Benefits of prebiotics include improvement in gut barrier function and host immunity, reduction of potentially pathogenic bacteria subpopulations (e.g. clostridia), and enhanced SCFA production. Inulin, oligofructose, and FOS have been extensively studied as prebiotics, and have been shown to significantly increase fecal bifidobacteria at fairly low levels of consumption (5-8 grams per day).20 While these are the most well-studied prebiotic fibres, the ability to favorably alter the intestinal microflora has been demonstrated by a number of other fibre sources. Acacia gum was shown to produce a greater increase in bifidobacteria and lactobacilli than an equal dose of inulin, and resulted in fewer gastrointestinal side effects, such as gas and bloating.21 Polydextrose consumption resulted in a dose-dependent decrease in bacteroides, as well as an increase in lactobacilli and bifidobacteria.7 Wheat dextrin has also been shown to increase lactobacilli and reduce Clostridium perfringens.22

Fermentable fibres, such as pectin and β-glucans, that don’t meet the definition for prebiotics still provide health benefits via production of SCFAs. The three most abundant SCFAs are acetate, propionate, and butyrate, each of which exerts unique physiological effects. Of these, butyrate is considered the most beneficial in terms of colonic health. Butyrate is the preferred energy source for colonic epithelial cells, and promotes normal cell differentiation and proliferation.23 SCFAs also help regulate sodium and water absorption, and can enhance absorption of calcium and other minerals. In addition, SCFAs act to lower colonic pH, which can inhibit

growth of potential pathogens and promote the growth of beneficial bacteria such as bifidobacteria and lactobacilli. Different fibres vary in the amounts and ratio of SCFA produced, as well as in the rate of production. Fibres that are fermented quickly may lead to excessive gas production and bloating, so dose is an important consideration. Fermentation pattern may be related to the molecular weight, chain length, and structure of the fibre. Short chain molecules, such as FOS, are generally fermented more rapidly than larger, longer chain molecules such as acacia gum and partially hydrolyzed guar gum.

Immune Function and Inflammation

Some fibres may also play a role in improving immune function via production of SCFAs. In animal studies, addition of SCFAs to parenteral feeding caused an increase in T helper cells, macrophages, and neutrophils, and increased cytotoxic activity of natural killer cells.24 In humans, FOS consumption has been shown to increase T lymphocytes in adults and improve antibody response to a vaccine in infants.25,26 There is also some evidence of increased resistance to illness or infection with fibre intake. Oligofructose consumption was found to reduce febrile illness associated with diarrhea or respiratory events, and reduce antibiotic use in infants.27 Certain fibres, such as β-glucans, have been shown to interact with immune cells, and can therefore stimulate the immune system directly.28 Soluble, non-viscous fibre may also be potentially useful in alleviating symptoms of inflammatory conditions, such as irritable bowel syndrome (IBS). In particular, partially hydrolyzed guar gum has been shown to improve abdominal pain and bowel habits better than wheat bran and qualitative scores of epithelial injury and inflammation compared to control.29,30

Weight Regulation

Epidemiologic evidence suggests that increased intake of dietary fibre is protective against the development of obesity, and fibre consumption is inversely correlated with body weight and body fat. High fibre foods take longer to chew and tend to have a high volume and low energy density, which may help to promote satiety. Fibre also delays gastric emptying and nutrient absorption, which can extend feelings of fullness. Likewise, most studies with controlled energy intake indicate that dietary fibre increases feelings of satiety and reduces hunger following a meal.31 Viscous fibres, such as psyllium and guar gum, seem to be most successful at promoting satiety, but insoluble fibres, such as cellulose and wheat bran, have also been shown to be satiating.32 Other fibres, such as polydextrose, seem to have little effect on satiation.33

CONCLUSION:

Dietary fibres exhibit a diverse range of physiochemical properties and corresponding physiological effects. The role of fibre in health has extended far beyond improved laxation, and includes benefits on risk factors for cardiovascular disease, diabetes, weight management, immune function, and colonic health. However, it is clear that not all fibres are equal in terms of the types and extent of health benefits they provide. Characteristics such as solubility, fermentability, and viscosity are important determinants of the effect the fibre will have in the body. Due to the variability of fibre’s effects in the body, it is important to consume fibre from a variety of sources. In general, it is recommended to increase fibre consumption from whole foods, such as legumes, fruits, vegetables, and whole grains. Overall, increasing consumption of dietary fibre to recommended levels could play an important role in improving health of the general population.

References

1. Institute of Medicine of the National Academies. Dietary Reference Intakes: Energy, Carbohydrates, Fibre, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. Washington, D.C., USA: The National Academies Press; 2002.

2. Health Canada, Canadian Community Health Survey Cycle 2.2, Nutrition. (2004). Nutrient Intakes from Food. Provincial, Regional and National Summary Data Tables: Volume 1.

3. Slavin JL, Savarino V, Paredes-Diaz A, Fotopoulos G. A review of the role of soluble fibre in health with specific reference to wheat dextrin. J Int Med Res. 2009;37:1-17.

4. Kurasawa S, Haack VS, Marlett JA. Plant residue and bacteria as bases for increased stool weight accompanying consumption of higher dietary fibre diets. J Am Coll Nutr. 2000;19:426-433.

5. Cummings JH. The effect of dietary fibre on fecal weight and composition. In: Spiller GA, ed. CRC Handbook of Dietary Fibre in Human Nutrition. Boca Raton, FL: CRC Press; 1993:263-333.

6. Gibson GR, Beatty ER, Wang X, Cummings JH. Selective stimulation of bifidobacteria in the human colon by oligofructose and inulin. Gastroenterology. 1995;108:975-982.

7. Jie Z, Bang-Yao L, Ming-Jie X, et al. Studies on the effects of polydextrose intake on physiologic functions in chinese people. Am J Clin Nutr. 2000;72:1503-1509.

8. Ashraf W, Park F, Lof J, Quigley EM. Effects of psyllium therapy on stool characteristics, colon transit and anorectal function in chronic idiopathic constipation. Aliment Pharmacol Ther. 1995;9:639-647.

9. Pereira MA, Ludwig DS. Dietary fibre and body-weight regulation. observations and mechanisms. Pediatr Clin North Am. 2001;48:969-980.

10. Anderson JW, Baird P, Davis RH,Jr, et al. Health benefits of dietary fibre. Nutr Rev. 2009;67:188-205.

11. Anderson JW, Davidson MH, Blonde L, et al. Long-term cholesterol-lowering effects of psyllium as an adjunct to diet therapy in the treatment of hypercholesterolemia. Am J Clin Nutr. 2000;71:1433-1438.

12. Tuomilehto J, Silvasti M, Aro A, et al. Long term treatment of severe hypercholesterolaemia with guar gum. Atherosclerosis. 1988;72:157-162.

13. Trautwein EA, Kunath-Rau A, Erbersdobler HF. Increased fecal bile acid excretion and changes in the circulating bile acid pool are involved in the hypocholesterolemic and gallstone-preventive actions of psyllium in hamsters. J Nutr. 1999;129:896-902.

14. Wright RS, Anderson JW, Bridges SR. Propionate inhibits hepatocyte lipid synthesis. Proc Soc Exp Biol Med. 1990;195:26-29.

15. Salmeron J, Manson JE, Stampfer MJ, Colditz GA, Wing AL, Willett WC. Dietary fibre, glycemic load, and risk of non-insulin-dependent diabetes mellitus in women. JAMA. 1997;277:472-477.

16. Mineo H, Hashizume Y, Hanaki Y, et al. Chemical specificity of short-chain fatty acids in stimulating insulin and glucagon secretion in sheep. Am J Physiol. 1994;267:E234-41.

17. Brighenti F, Casiraghi MC, Canzi E, Ferrari A. Effect of consumption of a ready-to-eat breakfast cereal containing inulin on the intestinal milieu and blood lipids in healthy male volunteers. Eur J Clin Nutr. 1999;53:726-733.

18. Yamashita K, Kawai K, Itakura M. Effects of fructo-oligosaccharides on blood glucose and serum lipids in diabetic subjects. Nutr Research. 1984;4:961-966.

19. Gibson GR, Roberfroid MB. Dietary modulation of the human colonic microbiota: Introducing the concept of prebiotics. J Nutr. 1995;125:1401-1412.

20. Kolida S, Gibson GR. Prebiotic capacity of inulin-type fructans. J Nutr. 2007;137:2503S-2506S.

21. Calame W, Weseler AR, Viebke C, Flynn C, Siemensma AD. Gum arabic establishes prebiotic functionality in healthy human volunteers in a dose-dependent manner. Br J Nutr. 2008;100:1269-1275.

22. Pasman W, Wils D, Saniez MH, Kardinaal A. Long-term gastrointestinal tolerance of NUTRIOSE FB in healthy men. Eur J Clin Nutr. 2006;60:1024-1034.

23. Topping DL, Clifton PM. Short-chain fatty acids and human colonic function: Roles of resistant starch and nonstarch polysaccharides. Physiol Rev. 2001;81:1031-1064.

24. Pratt VC, Tappenden KA, McBurney MI, Field CJ. Short-chain fatty acid-supplemented total parenteral nutrition improves nonspecific immunity after intestinal resection in rats. JPEN J Parenter Enteral Nutr. 1996;20:264-271.

25. Guigoz Y, Rochat F, Perruisseau-Carrier G, Rochat I, Schiffrin E. Effects of oligosaccharides on the faecal flora and nonspecific immune system in elderly people. Nutrition Research. 2002;22:13.

26. Firmansyah A, Pramita G, Fassler C, Haschke F, Link-Amster H. Improved humoral immune response to measles vaccine in infants receiving infant cereal with fructo-oligosaccharides. Journal of Paediatric Gastroenterology and Nutrition. 2001;31:A521.

27. Saavedra JM, Tschernia A. Human studies with probiotics and prebiotics: Clinical implications. Br J Nutr. 2002;87 Suppl 2:S241-6.

28. Vetvicka V, Thornton BP, Ross GD. Soluble beta-glucan polysaccharide binding to the lectin site of neutrophil or natural killer cell complement receptor type 3 (CD11b/CD18) generates a primed state of the receptor capable of mediating cytotoxicity of iC3b-opsonized target cells. J Clin Invest. 1996;98:50-61.

29. Parisi GC, Zilli M, Miani MP, et al. High-fibre diet supplementation in patients with irritable bowel syndrome (IBS): A multicenter, randomized, open trial comparison between wheat bran diet and partially hydrolyzed guar gum (PHGG). Dig Dis Sci. 2002;47:1697-1704.

30. Garcia Peris P, Cuerda Compes C, Camblor Alvarez M. Dieta enteral polimerica estandar vs. dieta polimerica con fibra soluble en pacientes con colitis ulcerosa. Rev Esp Enf Digest. 1997;87:86.

31. Howarth NC, Saltzman E, Roberts SB. Dietary fibre and weight regulation. Nutr Rev. 2001;59:129-139.

32. Slavin J, Green H. Dietary fibre and satiety. Nutrition Bulletin. 2007;32:32-42. 33. Willis HJ, Eldridge AL, Beiseigel J, Thomas W, Slavin JL. Greater satiety response

with resistant starch and corn bran in human subjects. Nutr Res. 2009;29:100-105.

Fast Fibre Facts: Different Fibres, Different Impact on Health

1. Wheat Bran Fibre is the Best Fibre for Promoting Regularity In scientific studies on regularity, wheat bran is generally seen as

the “gold standard” against which other fibres are measured for efficacy.1 Look for products that have wheat bran or whole wheat as the first ingredient.

2. Soluble Fibres Lower Blood LDL Cholesterol Levels Psyllium fibre, β-glucan from oats and pectin rich fruits such as pears and apples are some

examples of soluble fibres that act like a sponge in the digestive system, soaking up cholesterol and helping to remove it from the body.

3. Prebiotic Fibres Stimulate the Growth of Healthy Bacteria in the Digestive System There are many healthy bacteria in the digestive tract that play important roles in helping

maintain health. By stimulating the growth of healthy bacteria, inulin and other prebiotic fibres have been shown to have a positive impact on immunity, calcium absorption and overall digestive health. Asparagus, leeks and Jerusalem artichokes naturally contain prebiotics. Prebiotics are also found in some dairy products like yogurt and cottage cheese and cereal products like the examples below that provide a source of prebiotic fibre.

In general, eating a healthy diet high in fibre has many proven health benefits ranging from promotion of a healthy digestive system to weight management to blood sugar management.

The following provide a few, quick Fast Facts on the role specific types of fibres play in health:

1. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein and Amino Acids. Institute of Medicine (U.S.). Panel on Macronutrients, Institute of Medicine (U.S.). Standing Committee on the Scientific Evaluation of Dietary Reference Intakes 2005

2. US Department of Health and Human Services. National Institute of Health. http://www.nhlbi.nih.gov/chd/Tipsheets/solfiber.htm

* © 2010, Trademark of Kellogg Company used under licence by Kellogg Canada Inc.

As an example, the first ingredient in All-Bran Buds* cereal is wheat bran.

Kellogg’s Guardian* cereal provides 4 g of soluble psyllium fibre per 1 cup (34 g) serving.

Fruits such as pears, apples and citrus fruits provide between 1 to 2 g of soluble fibre per 1 medium fruit.2

Fibre Plus Bars Kashi* GoLean Crunch!* cereal

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Abby Klosterbuer, BSc. PhD (cand.)

Abby Klosterbuer is currently a Ph.D. candidate at the Department of Food Science and Nutrition at the University of Minnesota, under the supervision of Dr. Joanne Slavin. Her Ph.D. work focuses on the effects of dietary fiber on satiety, glucose and inulin

release, gut hormones, and gut microflora. Abby is currently enrolled in her dietetic internship to become a Registered Dietitian.

SUMMER 2010 Vol 71 No 2 INSERT TO THE CANADIAN JOURNAL OF DIETETIC PRACTICE AND RESEARCH

Brought to you by the team of Registered Dietitians & Nutrition Professionals at

w w w . k e l l o g g s n u t r i t i o n . c a

Functionality of Different Fibres and Their Effects on Human Health

Joanne Slavin, PhD, RD.

Dr. Joanne Slavin is a professor in the Department of Food Science and Nutrition at the University of Minnesota. She has presented more than 250 invited scientific lectures around the world on topics including dietary fiber, carbohydrates, whole grains, and the role of diet in disease prevention. She is the author of more than 150 scientific publications and numerous book chapters and review articles. She is a Science Communicator for the Institute of Food Technologists and a member of numerous scientific societies, including the American Dietetic Association and the American

Society for Nutrition. She is a frequent source for the media on topics ranging from functional foods to sports nutrition. Dr. Slavin received B.S., M.S., and Ph.D. degrees in Nutritional Sciences from the University of Wisconsin-Madison and is a Registered Dietitian.

Dietary fibre is widely recognized as beneficial for overall human health, and high fibre intake is associated with reduced risk for a number of chronic conditions. The Institute of Medicine defines fibre in two parts: dietary fibre, which consists of nondigestible carbohydrate and lignin that are intrinsic and intact in plants, and functional fibre, which consists of isolated, nondigestible carbohydrates that have beneficial physiological effects in humans. Fibre was first included as a nutrient in the Dietary Reference Intakes (DRIs) in 2002, and the current recommendations are for individuals to consume between 25-38 grams of fibre per day.1 However, Canadians’ fibre intake falls dramatically short of the recommendations, with average intakes of both children and adults at about half of the Adequate intake levels.2

It is well recognized that different fibers exert different physiological effects. Traditionally, dietary fiber has been classified according to its solubility. In general, soluble fibers are considered to have benefits on serum lipids, while insoluble fibers are linked with laxation benefits. However, scientific evidence supporting that all soluble fibers lower cholesterol and all insoluble fibers increase stool weight is inconsistent. Many fiber sources, including oat bran and psyllium, are mostly soluble but still enlarge stool weight, however, wheat bran fibre is the only fibre to attain significant scientific agreement and be recognized as the gold standard for increasing stool weight by the Institute of Medicine.1

Increasingly, research indicates that additional properties, such as viscosity and fermentability, are more important characteristics in terms of physiological benefits. Viscous fibres are those that have gel-forming properties in the intestinal tract, and fermentable fibres are those that can

be metabolized by colonic bacteria. In general, soluble fibres are more completely fermented and have a higher viscosity than insoluble fibres. However, not all soluble fibres are viscous (e.g. partially hydrolyzed guar gum and acacia gum) and some insoluble fibres may be well fermented. Table 1 summarizes the classification of fibres based on these characteristics.3 It is clear that the term fibre encompasses a diverse range of substances with varying physiochemical properties and physiological effects.

Dietary Fibre Functional Fibre• Lignin • Resistant dextrins • Cellulose • Psyllium• B-glucans • Fructooligosaccharides• Hemicelluloses • Polydextrose • Pectins• Gums• Resistant Starch

Soluble Fibres Insoluble Fibres• B-glucans • Cellulose• Gums • Lignin• Wheat dextrin • Some pectins• Psyllium • Some hemicelluloses• Pectin Primary sources: wheat • Fructooligosaccharides bran, some vegetables• Inulin• Some hemicelluloses

Primary sources: oat products, legumes

Fermentable Fibre Non-fermentable Fibres• Wheat dextrin • Cellulose• Pectins • Lignin• B-glucans Primary sources: cereal fibres • Guar gum rich in cellulose (e.g. wheat bran)• Partially hydrolyzed guar gum• Inulin and oligofructose• Fructooligosaccharides

Primary sources: oats, barley, fruits and vegetables

Viscous Fibres Non-viscous Fibres• Pectins • Cellulose• B-glucans • Lignin• Some gums (e.g. guar gum) • Some hemicelluloses• Psyllium

Adapted from: Slavin et al. Journal of International Medical Research. 2009; 37:1-17

Table 1: Classification of fibres based on four characteristics

Average increase in fecal weight per gram fibre fed

Wheat 5.4 g/g fibre fed

Psyllium 4.0 g/g fibre fed

Cellulose 3.5 g/g fibre fed

Oats 3.4 g/g fibre fed

Corn 3.3 g/g fibre fed

Legumes 2.2 g/g fibre fed

Pectin 1.2 g/g fibre fed

Source: Cumming JH. 1993. CRC Handbook of Dietary Fibre

Table 2

Unlike in the United States, the following fibres can be used as ingredients in Canada, but according to labeling regulations, do not contribute to the total fibre value found in the Nutrition Facts table.

• Polydextrose

• Fructooligosaccharide

• Oligofructose

Effects of soluble fibre intake on serum LDL-cholesterol

Fibre Number Number Grams fibre/day Weighted net of Trials of Subjects (median) change (%)

Barley β -glucan 9 129 5 -11.1

Guar gum 4 79 15 -10.6

Oat β -glucan 13 457 6 -5.3

Pectin 5 71 15 -13.0

Psyllium 9 494 6 -5.5

Adapted from: Anderson JW, et al. Nutrition Reviews. 2009; 67(4):188-205

Table 3

HEALTH BENEFITS OF DIETARY FIBRE

Laxation and RegularityIt is well recognized that fibre is important for normal laxation. This is due primarily to the ability of fibre to increase stool weight. The increased weight is due to the physical presence of the fibre itself, water held by the fibre, and increased bacterial mass from fermentation.4 Larger and softer stools increase the ease of defecation and reduce transit time through the intestinal tract, which may help to prevent or relieve constipation. In general, cereal fibres are the most effective at increasing stool weight. Wheat bran is considered the “gold standard” when it comes to fecal bulking, since no other fibre or laxative has been shown to be as effective. Table 2 summarizes the ability of different fibres to increase stool weight.5

Not only insoluble fibres have an effect on laxation. Short Chain Fatty Acids, or SCFAs produced from fermentation of soluble fibres contribute to fecal bulk and increase the water content of feces. Inulin and oligofructose have been shown to increase fecal weight, as has polydextrose; however, significant scientific agreement has not been attained with these fibres.6,7 In addition, psyllium has been shown to have a range of effects, including increased stool frequency, increased stool weight, and improved stool consistency.8

Cholesterol Lowering

High fibre intake is associated with a lower prevalence of coronary heart disease.9 This may be due to the modifying effect certain fibres have on cardiovascular risk factors. Soluble, viscous fibres have been shown to significantly lower serum cholesterol levels. Table 3 summarizes the results of randomized, controlled trials examining the effect of soluble fibre on LDL cholesterol.10 The net changes in cholesterol (change with fibre treatment minus change with placebo) were weighted by number of subjects per trial.

The FDA has approved health claims for psyllium and β-glucan, two common sources of soluble fibre, in relation to reduced risk for coronary heart disease. The FDA concluded that 10.2 g/d of psyllium (providing 7 g of viscous fibre) or ≥3 g of β-glucan from oats should be consumed to achieve significant reductions in LDL cholesterol. While most studies are fairly short in duration, a few longer term studies with psyllium (6 months)

and guar gum (12 months) indicate that cholesterol reductions may be maintained with chronic consumption.11,12 The effects of these soluble fibres on serum lipids seem to be limited to LDL-cholesterol, and are not associated with changes in HDL-cholesterol or triglycerides. Health Canada is currently reviewing this claim for permissibility in Canada.

The mechanism for the cholesterol-lowering effects of soluble fibre is likely related to the ability of fibre to increase bile acid excretion. Bile acids are produced in the liver from cholesterol, and enter the small intestine, where they may be bound by fibre and eliminated in the feces. Increased loss requires the liver to use more cholesterol for bile acid synthesis, thus reducing the body’s cholesterol pool.13 In addition, short-chain fatty acid production from colonic fermentation of soluble fibres is thought to suppress hepatic cholesterol synthesis, which may contribute to this effect.14

Improved Glycemic and Insulinemic Response

Soluble fibre has also been shown to decrease glycemia and insulinemia. This may be related to the viscosity of the fibre. Viscous fibres, such as psyllium, β-glucan, and pectin, may form a gel in the small intestine, which acts to delay nutrient absorption, thus slowing delivery of glucose into the bloodstream and reducing the need for insulin. The ability of these fibres to lower postprandial glycemia and insulinemia has been established in numerous studies, but long-term effects are less well known. One study followed over 65,000 women for 6 years and found that dietary fibre intake was inversely associated with the development of type 2 diabetes.15

In addition, SCFAs produced from non-viscous, fermentable fibres may stimulate release of insulin from the pancreas and alter glycogen breakdown by the liver and so play a role in glucose metabolism.16 Consumption of inulin resulted in a significant decrease in fasting insulin concentrations, and intake of Fructooligosaccharides (FOS) caused a reduction in fasting glucose in patients with type 2 diabetes.17,18 In general, the effects of fibre on glucose and insulin levels are more pronounced in individuals with diabetes mellitus.

Prebiotic Effect and SCFA Production

Fermentable fibres may provide a number of health benefits by altering the composition of the intestinal flora. Prebiotics are non-digestible substances that provide a beneficial physiological effect to the host by selectively stimulating the favorable growth or activity of a limited number of indigenous bacteria.19 This generally refers to the ability of a fibre to increase the growth of bifidobacteria and lactobacilli, which are considered beneficial to human health. Benefits of prebiotics include improvement in gut barrier function and host immunity, reduction of potentially pathogenic bacteria subpopulations (e.g. clostridia), and enhanced SCFA production. Inulin, oligofructose, and FOS have been extensively studied as prebiotics, and have been shown to significantly increase fecal bifidobacteria at fairly low levels of consumption (5-8 grams per day).20 While these are the most well-studied prebiotic fibres, the ability to favorably alter the intestinal microflora has been demonstrated by a number of other fibre sources. Acacia gum was shown to produce a greater increase in bifidobacteria and lactobacilli than an equal dose of inulin, and resulted in fewer gastrointestinal side effects, such as gas and bloating.21 Polydextrose consumption resulted in a dose-dependent decrease in bacteroides, as well as an increase in lactobacilli and bifidobacteria.7 Wheat dextrin has also been shown to increase lactobacilli and reduce Clostridium perfringens.22

Fermentable fibres, such as pectin and β-glucans, that don’t meet the definition for prebiotics still provide health benefits via production of SCFAs. The three most abundant SCFAs are acetate, propionate, and butyrate, each of which exerts unique physiological effects. Of these, butyrate is considered the most beneficial in terms of colonic health. Butyrate is the preferred energy source for colonic epithelial cells, and promotes normal cell differentiation and proliferation.23 SCFAs also help regulate sodium and water absorption, and can enhance absorption of calcium and other minerals. In addition, SCFAs act to lower colonic pH, which can inhibit

growth of potential pathogens and promote the growth of beneficial bacteria such as bifidobacteria and lactobacilli. Different fibres vary in the amounts and ratio of SCFA produced, as well as in the rate of production. Fibres that are fermented quickly may lead to excessive gas production and bloating, so dose is an important consideration. Fermentation pattern may be related to the molecular weight, chain length, and structure of the fibre. Short chain molecules, such as FOS, are generally fermented more rapidly than larger, longer chain molecules such as acacia gum and partially hydrolyzed guar gum.

Immune Function and Inflammation

Some fibres may also play a role in improving immune function via production of SCFAs. In animal studies, addition of SCFAs to parenteral feeding caused an increase in T helper cells, macrophages, and neutrophils, and increased cytotoxic activity of natural killer cells.24 In humans, FOS consumption has been shown to increase T lymphocytes in adults and improve antibody response to a vaccine in infants.25,26 There is also some evidence of increased resistance to illness or infection with fibre intake. Oligofructose consumption was found to reduce febrile illness associated with diarrhea or respiratory events, and reduce antibiotic use in infants.27 Certain fibres, such as β-glucans, have been shown to interact with immune cells, and can therefore stimulate the immune system directly.28 Soluble, non-viscous fibre may also be potentially useful in alleviating symptoms of inflammatory conditions, such as irritable bowel syndrome (IBS). In particular, partially hydrolyzed guar gum has been shown to improve abdominal pain and bowel habits better than wheat bran and qualitative scores of epithelial injury and inflammation compared to control.29,30

Weight Regulation

Epidemiologic evidence suggests that increased intake of dietary fibre is protective against the development of obesity, and fibre consumption is inversely correlated with body weight and body fat. High fibre foods take longer to chew and tend to have a high volume and low energy density, which may help to promote satiety. Fibre also delays gastric emptying and nutrient absorption, which can extend feelings of fullness. Likewise, most studies with controlled energy intake indicate that dietary fibre increases feelings of satiety and reduces hunger following a meal.31 Viscous fibres, such as psyllium and guar gum, seem to be most successful at promoting satiety, but insoluble fibres, such as cellulose and wheat bran, have also been shown to be satiating.32 Other fibres, such as polydextrose, seem to have little effect on satiation.33

CONCLUSION:

Dietary fibres exhibit a diverse range of physiochemical properties and corresponding physiological effects. The role of fibre in health has extended far beyond improved laxation, and includes benefits on risk factors for cardiovascular disease, diabetes, weight management, immune function, and colonic health. However, it is clear that not all fibres are equal in terms of the types and extent of health benefits they provide. Characteristics such as solubility, fermentability, and viscosity are important determinants of the effect the fibre will have in the body. Due to the variability of fibre’s effects in the body, it is important to consume fibre from a variety of sources. In general, it is recommended to increase fibre consumption from whole foods, such as legumes, fruits, vegetables, and whole grains. Overall, increasing consumption of dietary fibre to recommended levels could play an important role in improving health of the general population.

References

1. Institute of Medicine of the National Academies. Dietary Reference Intakes: Energy, Carbohydrates, Fibre, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. Washington, D.C., USA: The National Academies Press; 2002.

2. Health Canada, Canadian Community Health Survey Cycle 2.2, Nutrition. (2004). Nutrient Intakes from Food. Provincial, Regional and National Summary Data Tables: Volume 1.

3. Slavin JL, Savarino V, Paredes-Diaz A, Fotopoulos G. A review of the role of soluble fibre in health with specific reference to wheat dextrin. J Int Med Res. 2009;37:1-17.

4. Kurasawa S, Haack VS, Marlett JA. Plant residue and bacteria as bases for increased stool weight accompanying consumption of higher dietary fibre diets. J Am Coll Nutr. 2000;19:426-433.

5. Cummings JH. The effect of dietary fibre on fecal weight and composition. In: Spiller GA, ed. CRC Handbook of Dietary Fibre in Human Nutrition. Boca Raton, FL: CRC Press; 1993:263-333.

6. Gibson GR, Beatty ER, Wang X, Cummings JH. Selective stimulation of bifidobacteria in the human colon by oligofructose and inulin. Gastroenterology. 1995;108:975-982.

7. Jie Z, Bang-Yao L, Ming-Jie X, et al. Studies on the effects of polydextrose intake on physiologic functions in chinese people. Am J Clin Nutr. 2000;72:1503-1509.

8. Ashraf W, Park F, Lof J, Quigley EM. Effects of psyllium therapy on stool characteristics, colon transit and anorectal function in chronic idiopathic constipation. Aliment Pharmacol Ther. 1995;9:639-647.

9. Pereira MA, Ludwig DS. Dietary fibre and body-weight regulation. observations and mechanisms. Pediatr Clin North Am. 2001;48:969-980.

10. Anderson JW, Baird P, Davis RH,Jr, et al. Health benefits of dietary fibre. Nutr Rev. 2009;67:188-205.

11. Anderson JW, Davidson MH, Blonde L, et al. Long-term cholesterol-lowering effects of psyllium as an adjunct to diet therapy in the treatment of hypercholesterolemia. Am J Clin Nutr. 2000;71:1433-1438.

12. Tuomilehto J, Silvasti M, Aro A, et al. Long term treatment of severe hypercholesterolaemia with guar gum. Atherosclerosis. 1988;72:157-162.

13. Trautwein EA, Kunath-Rau A, Erbersdobler HF. Increased fecal bile acid excretion and changes in the circulating bile acid pool are involved in the hypocholesterolemic and gallstone-preventive actions of psyllium in hamsters. J Nutr. 1999;129:896-902.

14. Wright RS, Anderson JW, Bridges SR. Propionate inhibits hepatocyte lipid synthesis. Proc Soc Exp Biol Med. 1990;195:26-29.

15. Salmeron J, Manson JE, Stampfer MJ, Colditz GA, Wing AL, Willett WC. Dietary fibre, glycemic load, and risk of non-insulin-dependent diabetes mellitus in women. JAMA. 1997;277:472-477.

16. Mineo H, Hashizume Y, Hanaki Y, et al. Chemical specificity of short-chain fatty acids in stimulating insulin and glucagon secretion in sheep. Am J Physiol. 1994;267:E234-41.

17. Brighenti F, Casiraghi MC, Canzi E, Ferrari A. Effect of consumption of a ready-to-eat breakfast cereal containing inulin on the intestinal milieu and blood lipids in healthy male volunteers. Eur J Clin Nutr. 1999;53:726-733.

18. Yamashita K, Kawai K, Itakura M. Effects of fructo-oligosaccharides on blood glucose and serum lipids in diabetic subjects. Nutr Research. 1984;4:961-966.

19. Gibson GR, Roberfroid MB. Dietary modulation of the human colonic microbiota: Introducing the concept of prebiotics. J Nutr. 1995;125:1401-1412.

20. Kolida S, Gibson GR. Prebiotic capacity of inulin-type fructans. J Nutr. 2007;137:2503S-2506S.

21. Calame W, Weseler AR, Viebke C, Flynn C, Siemensma AD. Gum arabic establishes prebiotic functionality in healthy human volunteers in a dose-dependent manner. Br J Nutr. 2008;100:1269-1275.

22. Pasman W, Wils D, Saniez MH, Kardinaal A. Long-term gastrointestinal tolerance of NUTRIOSE FB in healthy men. Eur J Clin Nutr. 2006;60:1024-1034.

23. Topping DL, Clifton PM. Short-chain fatty acids and human colonic function: Roles of resistant starch and nonstarch polysaccharides. Physiol Rev. 2001;81:1031-1064.

24. Pratt VC, Tappenden KA, McBurney MI, Field CJ. Short-chain fatty acid-supplemented total parenteral nutrition improves nonspecific immunity after intestinal resection in rats. JPEN J Parenter Enteral Nutr. 1996;20:264-271.

25. Guigoz Y, Rochat F, Perruisseau-Carrier G, Rochat I, Schiffrin E. Effects of oligosaccharides on the faecal flora and nonspecific immune system in elderly people. Nutrition Research. 2002;22:13.

26. Firmansyah A, Pramita G, Fassler C, Haschke F, Link-Amster H. Improved humoral immune response to measles vaccine in infants receiving infant cereal with fructo-oligosaccharides. Journal of Paediatric Gastroenterology and Nutrition. 2001;31:A521.

27. Saavedra JM, Tschernia A. Human studies with probiotics and prebiotics: Clinical implications. Br J Nutr. 2002;87 Suppl 2:S241-6.

28. Vetvicka V, Thornton BP, Ross GD. Soluble beta-glucan polysaccharide binding to the lectin site of neutrophil or natural killer cell complement receptor type 3 (CD11b/CD18) generates a primed state of the receptor capable of mediating cytotoxicity of iC3b-opsonized target cells. J Clin Invest. 1996;98:50-61.

29. Parisi GC, Zilli M, Miani MP, et al. High-fibre diet supplementation in patients with irritable bowel syndrome (IBS): A multicenter, randomized, open trial comparison between wheat bran diet and partially hydrolyzed guar gum (PHGG). Dig Dis Sci. 2002;47:1697-1704.

30. Garcia Peris P, Cuerda Compes C, Camblor Alvarez M. Dieta enteral polimerica estandar vs. dieta polimerica con fibra soluble en pacientes con colitis ulcerosa. Rev Esp Enf Digest. 1997;87:86.

31. Howarth NC, Saltzman E, Roberts SB. Dietary fibre and weight regulation. Nutr Rev. 2001;59:129-139.

32. Slavin J, Green H. Dietary fibre and satiety. Nutrition Bulletin. 2007;32:32-42. 33. Willis HJ, Eldridge AL, Beiseigel J, Thomas W, Slavin JL. Greater satiety response

with resistant starch and corn bran in human subjects. Nutr Res. 2009;29:100-105.

Fast Fibre Facts: Different Fibres, Different Impact on Health

1. Wheat Bran Fibre is the Best Fibre for Promoting Regularity In scientific studies on regularity, wheat bran is generally seen as

the “gold standard” against which other fibres are measured for efficacy.1 Look for products that have wheat bran or whole wheat as the first ingredient.

2. Soluble Fibres Lower Blood LDL Cholesterol Levels Psyllium fibre, β-glucan from oats and pectin rich fruits such as pears and apples are some

examples of soluble fibres that act like a sponge in the digestive system, soaking up cholesterol and helping to remove it from the body.

3. Prebiotic Fibres Stimulate the Growth of Healthy Bacteria in the Digestive System There are many healthy bacteria in the digestive tract that play important roles in helping

maintain health. By stimulating the growth of healthy bacteria, inulin and other prebiotic fibres have been shown to have a positive impact on immunity, calcium absorption and overall digestive health. Asparagus, leeks and Jerusalem artichokes naturally contain prebiotics. Prebiotics are also found in some dairy products like yogurt and cottage cheese and cereal products like the examples below that provide a source of prebiotic fibre.

In general, eating a healthy diet high in fibre has many proven health benefits ranging from promotion of a healthy digestive system to weight management to blood sugar management.

The following provide a few, quick Fast Facts on the role specific types of fibres play in health:

1. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein and Amino Acids. Institute of Medicine (U.S.). Panel on Macronutrients, Institute of Medicine (U.S.). Standing Committee on the Scientific Evaluation of Dietary Reference Intakes 2005

2. US Department of Health and Human Services. National Institute of Health. http://www.nhlbi.nih.gov/chd/Tipsheets/solfiber.htm

* © 2010, Trademark of Kellogg Company used under licence by Kellogg Canada Inc.

As an example, the first ingredient in All-Bran Buds* cereal is wheat bran.

Kellogg’s Guardian* cereal provides 4 g of soluble psyllium fibre per 1 cup (34 g) serving.

Fruits such as pears, apples and citrus fruits provide between 1 to 2 g of soluble fibre per 1 medium fruit.2

Fibre Plus Bars Kashi* GoLean Crunch!* cereal

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Abby Klosterbuer, BSc. PhD (cand.)

Abby Klosterbuer is currently a Ph.D. candidate at the Department of Food Science and Nutrition at the University of Minnesota, under the supervision of Dr. Joanne Slavin. Her Ph.D. work focuses on the effects of dietary fiber on satiety, glucose and inulin

release, gut hormones, and gut microflora. Abby is currently enrolled in her dietetic internship to become a Registered Dietitian.

SUMMER 2010 Vol 71 No 2 INSERT TO THE CANADIAN JOURNAL OF DIETETIC PRACTICE AND RESEARCH

Brought to you by the team of Registered Dietitians & Nutrition Professionals at

w w w . k e l l o g g s n u t r i t i o n . c a

Functionality of Different Fibres and Their Effects on Human Health

Joanne Slavin, PhD, RD.

Dr. Joanne Slavin is a professor in the Department of Food Science and Nutrition at the University of Minnesota. She has presented more than 250 invited scientific lectures around the world on topics including dietary fiber, carbohydrates, whole grains, and the role of diet in disease prevention. She is the author of more than 150 scientific publications and numerous book chapters and review articles. She is a Science Communicator for the Institute of Food Technologists and a member of numerous scientific societies, including the American Dietetic Association and the American

Society for Nutrition. She is a frequent source for the media on topics ranging from functional foods to sports nutrition. Dr. Slavin received B.S., M.S., and Ph.D. degrees in Nutritional Sciences from the University of Wisconsin-Madison and is a Registered Dietitian.

Dietary fibre is widely recognized as beneficial for overall human health, and high fibre intake is associated with reduced risk for a number of chronic conditions. The Institute of Medicine defines fibre in two parts: dietary fibre, which consists of nondigestible carbohydrate and lignin that are intrinsic and intact in plants, and functional fibre, which consists of isolated, nondigestible carbohydrates that have beneficial physiological effects in humans. Fibre was first included as a nutrient in the Dietary Reference Intakes (DRIs) in 2002, and the current recommendations are for individuals to consume between 25-38 grams of fibre per day.1 However, Canadians’ fibre intake falls dramatically short of the recommendations, with average intakes of both children and adults at about half of the Adequate intake levels.2

It is well recognized that different fibers exert different physiological effects. Traditionally, dietary fiber has been classified according to its solubility. In general, soluble fibers are considered to have benefits on serum lipids, while insoluble fibers are linked with laxation benefits. However, scientific evidence supporting that all soluble fibers lower cholesterol and all insoluble fibers increase stool weight is inconsistent. Many fiber sources, including oat bran and psyllium, are mostly soluble but still enlarge stool weight, however, wheat bran fibre is the only fibre to attain significant scientific agreement and be recognized as the gold standard for increasing stool weight by the Institute of Medicine.1

Increasingly, research indicates that additional properties, such as viscosity and fermentability, are more important characteristics in terms of physiological benefits. Viscous fibres are those that have gel-forming properties in the intestinal tract, and fermentable fibres are those that can

be metabolized by colonic bacteria. In general, soluble fibres are more completely fermented and have a higher viscosity than insoluble fibres. However, not all soluble fibres are viscous (e.g. partially hydrolyzed guar gum and acacia gum) and some insoluble fibres may be well fermented. Table 1 summarizes the classification of fibres based on these characteristics.3 It is clear that the term fibre encompasses a diverse range of substances with varying physiochemical properties and physiological effects.

Dietary Fibre Functional Fibre• Lignin • Resistant dextrins • Cellulose • Psyllium• B-glucans • Fructooligosaccharides• Hemicelluloses • Polydextrose • Pectins• Gums• Resistant Starch

Soluble Fibres Insoluble Fibres• B-glucans • Cellulose• Gums • Lignin• Wheat dextrin • Some pectins• Psyllium • Some hemicelluloses• Pectin Primary sources: wheat • Fructooligosaccharides bran, some vegetables• Inulin• Some hemicelluloses

Primary sources: oat products, legumes

Fermentable Fibre Non-fermentable Fibres• Wheat dextrin • Cellulose• Pectins • Lignin• B-glucans Primary sources: cereal fibres • Guar gum rich in cellulose (e.g. wheat bran)• Partially hydrolyzed guar gum• Inulin and oligofructose• Fructooligosaccharides

Primary sources: oats, barley, fruits and vegetables

Viscous Fibres Non-viscous Fibres• Pectins • Cellulose• B-glucans • Lignin• Some gums (e.g. guar gum) • Some hemicelluloses• Psyllium

Adapted from: Slavin et al. Journal of International Medical Research. 2009; 37:1-17

Table 1: Classification of fibres based on four characteristics

Average increase in fecal weight per gram fibre fed

Wheat 5.4 g/g fibre fed

Psyllium 4.0 g/g fibre fed

Cellulose 3.5 g/g fibre fed

Oats 3.4 g/g fibre fed

Corn 3.3 g/g fibre fed

Legumes 2.2 g/g fibre fed

Pectin 1.2 g/g fibre fed

Source: Cumming JH. 1993. CRC Handbook of Dietary Fibre

Table 2

Unlike in the United States, the following fibres can be used as ingredients in Canada, but according to labeling regulations, do not contribute to the total fibre value found in the Nutrition Facts table.

• Polydextrose

• Fructooligosaccharide

• Oligofructose

Effects of soluble fibre intake on serum LDL-cholesterol

Fibre Number Number Grams fibre/day Weighted net of Trials of Subjects (median) change (%)

Barley β -glucan 9 129 5 -11.1

Guar gum 4 79 15 -10.6

Oat β -glucan 13 457 6 -5.3

Pectin 5 71 15 -13.0

Psyllium 9 494 6 -5.5

Adapted from: Anderson JW, et al. Nutrition Reviews. 2009; 67(4):188-205

Table 3

HEALTH BENEFITS OF DIETARY FIBRE

Laxation and RegularityIt is well recognized that fibre is important for normal laxation. This is due primarily to the ability of fibre to increase stool weight. The increased weight is due to the physical presence of the fibre itself, water held by the fibre, and increased bacterial mass from fermentation.4 Larger and softer stools increase the ease of defecation and reduce transit time through the intestinal tract, which may help to prevent or relieve constipation. In general, cereal fibres are the most effective at increasing stool weight. Wheat bran is considered the “gold standard” when it comes to fecal bulking, since no other fibre or laxative has been shown to be as effective. Table 2 summarizes the ability of different fibres to increase stool weight.5

Not only insoluble fibres have an effect on laxation. Short Chain Fatty Acids, or SCFAs produced from fermentation of soluble fibres contribute to fecal bulk and increase the water content of feces. Inulin and oligofructose have been shown to increase fecal weight, as has polydextrose; however, significant scientific agreement has not been attained with these fibres.6,7 In addition, psyllium has been shown to have a range of effects, including increased stool frequency, increased stool weight, and improved stool consistency.8

Cholesterol Lowering

High fibre intake is associated with a lower prevalence of coronary heart disease.9 This may be due to the modifying effect certain fibres have on cardiovascular risk factors. Soluble, viscous fibres have been shown to significantly lower serum cholesterol levels. Table 3 summarizes the results of randomized, controlled trials examining the effect of soluble fibre on LDL cholesterol.10 The net changes in cholesterol (change with fibre treatment minus change with placebo) were weighted by number of subjects per trial.

The FDA has approved health claims for psyllium and β-glucan, two common sources of soluble fibre, in relation to reduced risk for coronary heart disease. The FDA concluded that 10.2 g/d of psyllium (providing 7 g of viscous fibre) or ≥3 g of β-glucan from oats should be consumed to achieve significant reductions in LDL cholesterol. While most studies are fairly short in duration, a few longer term studies with psyllium (6 months)

and guar gum (12 months) indicate that cholesterol reductions may be maintained with chronic consumption.11,12 The effects of these soluble fibres on serum lipids seem to be limited to LDL-cholesterol, and are not associated with changes in HDL-cholesterol or triglycerides. Health Canada is currently reviewing this claim for permissibility in Canada.

The mechanism for the cholesterol-lowering effects of soluble fibre is likely related to the ability of fibre to increase bile acid excretion. Bile acids are produced in the liver from cholesterol, and enter the small intestine, where they may be bound by fibre and eliminated in the feces. Increased loss requires the liver to use more cholesterol for bile acid synthesis, thus reducing the body’s cholesterol pool.13 In addition, short-chain fatty acid production from colonic fermentation of soluble fibres is thought to suppress hepatic cholesterol synthesis, which may contribute to this effect.14

Improved Glycemic and Insulinemic Response

Soluble fibre has also been shown to decrease glycemia and insulinemia. This may be related to the viscosity of the fibre. Viscous fibres, such as psyllium, β-glucan, and pectin, may form a gel in the small intestine, which acts to delay nutrient absorption, thus slowing delivery of glucose into the bloodstream and reducing the need for insulin. The ability of these fibres to lower postprandial glycemia and insulinemia has been established in numerous studies, but long-term effects are less well known. One study followed over 65,000 women for 6 years and found that dietary fibre intake was inversely associated with the development of type 2 diabetes.15

In addition, SCFAs produced from non-viscous, fermentable fibres may stimulate release of insulin from the pancreas and alter glycogen breakdown by the liver and so play a role in glucose metabolism.16 Consumption of inulin resulted in a significant decrease in fasting insulin concentrations, and intake of Fructooligosaccharides (FOS) caused a reduction in fasting glucose in patients with type 2 diabetes.17,18 In general, the effects of fibre on glucose and insulin levels are more pronounced in individuals with diabetes mellitus.

Prebiotic Effect and SCFA Production

Fermentable fibres may provide a number of health benefits by altering the composition of the intestinal flora. Prebiotics are non-digestible substances that provide a beneficial physiological effect to the host by selectively stimulating the favorable growth or activity of a limited number of indigenous bacteria.19 This generally refers to the ability of a fibre to increase the growth of bifidobacteria and lactobacilli, which are considered beneficial to human health. Benefits of prebiotics include improvement in gut barrier function and host immunity, reduction of potentially pathogenic bacteria subpopulations (e.g. clostridia), and enhanced SCFA production. Inulin, oligofructose, and FOS have been extensively studied as prebiotics, and have been shown to significantly increase fecal bifidobacteria at fairly low levels of consumption (5-8 grams per day).20 While these are the most well-studied prebiotic fibres, the ability to favorably alter the intestinal microflora has been demonstrated by a number of other fibre sources. Acacia gum was shown to produce a greater increase in bifidobacteria and lactobacilli than an equal dose of inulin, and resulted in fewer gastrointestinal side effects, such as gas and bloating.21 Polydextrose consumption resulted in a dose-dependent decrease in bacteroides, as well as an increase in lactobacilli and bifidobacteria.7 Wheat dextrin has also been shown to increase lactobacilli and reduce Clostridium perfringens.22

Fermentable fibres, such as pectin and β-glucans, that don’t meet the definition for prebiotics still provide health benefits via production of SCFAs. The three most abundant SCFAs are acetate, propionate, and butyrate, each of which exerts unique physiological effects. Of these, butyrate is considered the most beneficial in terms of colonic health. Butyrate is the preferred energy source for colonic epithelial cells, and promotes normal cell differentiation and proliferation.23 SCFAs also help regulate sodium and water absorption, and can enhance absorption of calcium and other minerals. In addition, SCFAs act to lower colonic pH, which can inhibit

growth of potential pathogens and promote the growth of beneficial bacteria such as bifidobacteria and lactobacilli. Different fibres vary in the amounts and ratio of SCFA produced, as well as in the rate of production. Fibres that are fermented quickly may lead to excessive gas production and bloating, so dose is an important consideration. Fermentation pattern may be related to the molecular weight, chain length, and structure of the fibre. Short chain molecules, such as FOS, are generally fermented more rapidly than larger, longer chain molecules such as acacia gum and partially hydrolyzed guar gum.

Immune Function and Inflammation

Some fibres may also play a role in improving immune function via production of SCFAs. In animal studies, addition of SCFAs to parenteral feeding caused an increase in T helper cells, macrophages, and neutrophils, and increased cytotoxic activity of natural killer cells.24 In humans, FOS consumption has been shown to increase T lymphocytes in adults and improve antibody response to a vaccine in infants.25,26 There is also some evidence of increased resistance to illness or infection with fibre intake. Oligofructose consumption was found to reduce febrile illness associated with diarrhea or respiratory events, and reduce antibiotic use in infants.27 Certain fibres, such as β-glucans, have been shown to interact with immune cells, and can therefore stimulate the immune system directly.28 Soluble, non-viscous fibre may also be potentially useful in alleviating symptoms of inflammatory conditions, such as irritable bowel syndrome (IBS). In particular, partially hydrolyzed guar gum has been shown to improve abdominal pain and bowel habits better than wheat bran and qualitative scores of epithelial injury and inflammation compared to control.29,30

Weight Regulation

Epidemiologic evidence suggests that increased intake of dietary fibre is protective against the development of obesity, and fibre consumption is inversely correlated with body weight and body fat. High fibre foods take longer to chew and tend to have a high volume and low energy density, which may help to promote satiety. Fibre also delays gastric emptying and nutrient absorption, which can extend feelings of fullness. Likewise, most studies with controlled energy intake indicate that dietary fibre increases feelings of satiety and reduces hunger following a meal.31 Viscous fibres, such as psyllium and guar gum, seem to be most successful at promoting satiety, but insoluble fibres, such as cellulose and wheat bran, have also been shown to be satiating.32 Other fibres, such as polydextrose, seem to have little effect on satiation.33

CONCLUSION:

Dietary fibres exhibit a diverse range of physiochemical properties and corresponding physiological effects. The role of fibre in health has extended far beyond improved laxation, and includes benefits on risk factors for cardiovascular disease, diabetes, weight management, immune function, and colonic health. However, it is clear that not all fibres are equal in terms of the types and extent of health benefits they provide. Characteristics such as solubility, fermentability, and viscosity are important determinants of the effect the fibre will have in the body. Due to the variability of fibre’s effects in the body, it is important to consume fibre from a variety of sources. In general, it is recommended to increase fibre consumption from whole foods, such as legumes, fruits, vegetables, and whole grains. Overall, increasing consumption of dietary fibre to recommended levels could play an important role in improving health of the general population.

References

1. Institute of Medicine of the National Academies. Dietary Reference Intakes: Energy, Carbohydrates, Fibre, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. Washington, D.C., USA: The National Academies Press; 2002.

2. Health Canada, Canadian Community Health Survey Cycle 2.2, Nutrition. (2004). Nutrient Intakes from Food. Provincial, Regional and National Summary Data Tables: Volume 1.

3. Slavin JL, Savarino V, Paredes-Diaz A, Fotopoulos G. A review of the role of soluble fibre in health with specific reference to wheat dextrin. J Int Med Res. 2009;37:1-17.

4. Kurasawa S, Haack VS, Marlett JA. Plant residue and bacteria as bases for increased stool weight accompanying consumption of higher dietary fibre diets. J Am Coll Nutr. 2000;19:426-433.

5. Cummings JH. The effect of dietary fibre on fecal weight and composition. In: Spiller GA, ed. CRC Handbook of Dietary Fibre in Human Nutrition. Boca Raton, FL: CRC Press; 1993:263-333.

6. Gibson GR, Beatty ER, Wang X, Cummings JH. Selective stimulation of bifidobacteria in the human colon by oligofructose and inulin. Gastroenterology. 1995;108:975-982.

7. Jie Z, Bang-Yao L, Ming-Jie X, et al. Studies on the effects of polydextrose intake on physiologic functions in chinese people. Am J Clin Nutr. 2000;72:1503-1509.

8. Ashraf W, Park F, Lof J, Quigley EM. Effects of psyllium therapy on stool characteristics, colon transit and anorectal function in chronic idiopathic constipation. Aliment Pharmacol Ther. 1995;9:639-647.

9. Pereira MA, Ludwig DS. Dietary fibre and body-weight regulation. observations and mechanisms. Pediatr Clin North Am. 2001;48:969-980.

10. Anderson JW, Baird P, Davis RH,Jr, et al. Health benefits of dietary fibre. Nutr Rev. 2009;67:188-205.

11. Anderson JW, Davidson MH, Blonde L, et al. Long-term cholesterol-lowering effects of psyllium as an adjunct to diet therapy in the treatment of hypercholesterolemia. Am J Clin Nutr. 2000;71:1433-1438.

12. Tuomilehto J, Silvasti M, Aro A, et al. Long term treatment of severe hypercholesterolaemia with guar gum. Atherosclerosis. 1988;72:157-162.

13. Trautwein EA, Kunath-Rau A, Erbersdobler HF. Increased fecal bile acid excretion and changes in the circulating bile acid pool are involved in the hypocholesterolemic and gallstone-preventive actions of psyllium in hamsters. J Nutr. 1999;129:896-902.

14. Wright RS, Anderson JW, Bridges SR. Propionate inhibits hepatocyte lipid synthesis. Proc Soc Exp Biol Med. 1990;195:26-29.

15. Salmeron J, Manson JE, Stampfer MJ, Colditz GA, Wing AL, Willett WC. Dietary fibre, glycemic load, and risk of non-insulin-dependent diabetes mellitus in women. JAMA. 1997;277:472-477.

16. Mineo H, Hashizume Y, Hanaki Y, et al. Chemical specificity of short-chain fatty acids in stimulating insulin and glucagon secretion in sheep. Am J Physiol. 1994;267:E234-41.

17. Brighenti F, Casiraghi MC, Canzi E, Ferrari A. Effect of consumption of a ready-to-eat breakfast cereal containing inulin on the intestinal milieu and blood lipids in healthy male volunteers. Eur J Clin Nutr. 1999;53:726-733.

18. Yamashita K, Kawai K, Itakura M. Effects of fructo-oligosaccharides on blood glucose and serum lipids in diabetic subjects. Nutr Research. 1984;4:961-966.

19. Gibson GR, Roberfroid MB. Dietary modulation of the human colonic microbiota: Introducing the concept of prebiotics. J Nutr. 1995;125:1401-1412.

20. Kolida S, Gibson GR. Prebiotic capacity of inulin-type fructans. J Nutr. 2007;137:2503S-2506S.

21. Calame W, Weseler AR, Viebke C, Flynn C, Siemensma AD. Gum arabic establishes prebiotic functionality in healthy human volunteers in a dose-dependent manner. Br J Nutr. 2008;100:1269-1275.

22. Pasman W, Wils D, Saniez MH, Kardinaal A. Long-term gastrointestinal tolerance of NUTRIOSE FB in healthy men. Eur J Clin Nutr. 2006;60:1024-1034.

23. Topping DL, Clifton PM. Short-chain fatty acids and human colonic function: Roles of resistant starch and nonstarch polysaccharides. Physiol Rev. 2001;81:1031-1064.

24. Pratt VC, Tappenden KA, McBurney MI, Field CJ. Short-chain fatty acid-supplemented total parenteral nutrition improves nonspecific immunity after intestinal resection in rats. JPEN J Parenter Enteral Nutr. 1996;20:264-271.

25. Guigoz Y, Rochat F, Perruisseau-Carrier G, Rochat I, Schiffrin E. Effects of oligosaccharides on the faecal flora and nonspecific immune system in elderly people. Nutrition Research. 2002;22:13.

26. Firmansyah A, Pramita G, Fassler C, Haschke F, Link-Amster H. Improved humoral immune response to measles vaccine in infants receiving infant cereal with fructo-oligosaccharides. Journal of Paediatric Gastroenterology and Nutrition. 2001;31:A521.

27. Saavedra JM, Tschernia A. Human studies with probiotics and prebiotics: Clinical implications. Br J Nutr. 2002;87 Suppl 2:S241-6.

28. Vetvicka V, Thornton BP, Ross GD. Soluble beta-glucan polysaccharide binding to the lectin site of neutrophil or natural killer cell complement receptor type 3 (CD11b/CD18) generates a primed state of the receptor capable of mediating cytotoxicity of iC3b-opsonized target cells. J Clin Invest. 1996;98:50-61.

29. Parisi GC, Zilli M, Miani MP, et al. High-fibre diet supplementation in patients with irritable bowel syndrome (IBS): A multicenter, randomized, open trial comparison between wheat bran diet and partially hydrolyzed guar gum (PHGG). Dig Dis Sci. 2002;47:1697-1704.

30. Garcia Peris P, Cuerda Compes C, Camblor Alvarez M. Dieta enteral polimerica estandar vs. dieta polimerica con fibra soluble en pacientes con colitis ulcerosa. Rev Esp Enf Digest. 1997;87:86.

31. Howarth NC, Saltzman E, Roberts SB. Dietary fibre and weight regulation. Nutr Rev. 2001;59:129-139.

32. Slavin J, Green H. Dietary fibre and satiety. Nutrition Bulletin. 2007;32:32-42. 33. Willis HJ, Eldridge AL, Beiseigel J, Thomas W, Slavin JL. Greater satiety response

with resistant starch and corn bran in human subjects. Nutr Res. 2009;29:100-105.

Fast Fibre Facts: Different Fibres, Different Impact on Health

1. Wheat Bran Fibre is the Best Fibre for Promoting Regularity In scientific studies on regularity, wheat bran is generally seen as

the “gold standard” against which other fibres are measured for efficacy.1 Look for products that have wheat bran or whole wheat as the first ingredient.

2. Soluble Fibres Lower Blood LDL Cholesterol Levels Psyllium fibre, β-glucan from oats and pectin rich fruits such as pears and apples are some

examples of soluble fibres that act like a sponge in the digestive system, soaking up cholesterol and helping to remove it from the body.

3. Prebiotic Fibres Stimulate the Growth of Healthy Bacteria in the Digestive System There are many healthy bacteria in the digestive tract that play important roles in helping

maintain health. By stimulating the growth of healthy bacteria, inulin and other prebiotic fibres have been shown to have a positive impact on immunity, calcium absorption and overall digestive health. Asparagus, leeks and Jerusalem artichokes naturally contain prebiotics. Prebiotics are also found in some dairy products like yogurt and cottage cheese and cereal products like the examples below that provide a source of prebiotic fibre.

In general, eating a healthy diet high in fibre has many proven health benefits ranging from promotion of a healthy digestive system to weight management to blood sugar management.

The following provide a few, quick Fast Facts on the role specific types of fibres play in health:

1. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein and Amino Acids. Institute of Medicine (U.S.). Panel on Macronutrients, Institute of Medicine (U.S.). Standing Committee on the Scientific Evaluation of Dietary Reference Intakes 2005

2. US Department of Health and Human Services. National Institute of Health. http://www.nhlbi.nih.gov/chd/Tipsheets/solfiber.htm

* © 2010, Trademark of Kellogg Company used under licence by Kellogg Canada Inc.

As an example, the first ingredient in All-Bran Buds* cereal is wheat bran.

Kellogg’s Guardian* cereal provides 4 g of soluble psyllium fibre per 1 cup (34 g) serving.

Fruits such as pears, apples and citrus fruits provide between 1 to 2 g of soluble fibre per 1 medium fruit.2

Fibre Plus Bars Kashi* GoLean Crunch!* cereal

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Schawk Creative Inc. 5350 Creekbank Rd., Mississauga, ON L4W 5S1 905.290.5312 905.290.5432

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