protein – essential nutrient and buildingblock for body...
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Protein – essential nutrient and buildingblock for body
tissueTina Beermann
Clinical Dietitian, Msc Clinical Nutrition
GreenSoul
Protein as a nutrient
Necessary vs. optimal intake/dietary needs regarding
Age
Fysical activity
Weightloss/weight maintenance/weightgain
Disease and injury
Protein quality – animal vs. plant proteins
Indespensable/essential amino acid composition
Bioavailability - Digestibility
Protein at a glance
• Proteins are large molecules consisting of one or more long chain of amino acids (AA).
• AA´s are organic compounds containing amine (-NH2) and carboxyl (-COOH) functional groups along with a side chain (R group) specific to each AA. Two AA contain a sulphur (S) compound in the side chain, methionine and cysteine.
• Proteins differ from one another in their sequence of AA’s and folding into a specific 3D structure that determines its activity.
• Proteins are vital in living organisms, giving structure to cells and tissues (e.g. muscle, skin, bones), and participate in virtually every process within the cell (enzymes, hormones, carriers, immunesystem).
• Some AA’s can be made by the body—generally synthetized from other amino acids—but some can not. The ones that can not be synthetized are known as essential amino acids (EAA) or indispensable amino acids (IAA).
Billede: https://da.wikipedia.org/wiki/Protein
Protein metabolism and the nitrogen pool• The human body dont a have a particular reserve pool of
proteins, unlike fat that can be stored i fat cells, or carbohydrate that can be stored as glycogen in small amounts in muscles and liver.
• We do have a free amino acid pool, that reflects the constant turnover of rebuilding and breakdown of proteins in the cell.
• The nitrogen or amino acid pool is a mixture of amino acids available in the cell derived from dietary sources or the degradation of protein.
• Each day our bodies synthesize proteins, AA, and other non-protein nitrogen containing compounds needed for growth, replacement and repair.
• Proteins in excess are used to supply energy or build reserves of glucose, glycogen or lipids.
• Some of the amino acids are catabolized producing energy and ammonia. The ammonia is converted to urea and excreted from the body and represents a drain on the nitrogen pool.
• Nitrogen balance is achieved when the dietary intake is balanced by the excretion of urea wastes.
Figur: http://chemistry.elmhurst.edu/vchembook/630proteinmet.html
Recommended protein intake
Healthy adults
• Nordic Nutrition Recommendations (NNR-2012): • 10-20 % of energy intake
• For the elderly: 15-20 %• 6-11 mo: 7-15 %• 12-23 mo: 10-15 %• 2-17 years: 10-20 %
• WHO:• EAR: 0.66 g protein/kg (BW)/d • RDA: 0.83 g/kg (BW)/day corresponding to the
97.5th percentile.
• For vegans: suggested (no consensus) 0.9 -1.0 g/kg (BW)/d
Nordic Nutrition Recommendations 2012 - Integrating nutrition and physical activity: http://dx.doi.org/10.6027/Nord2014-002Jack Norris: https://veganhealth.org/protein-part-2/
Dietary intake of protein in Denmark
DTU Fødevareinstituttet, Danskernes Kostvaner 2011-2013. https://www.food.dtu.dk/Publikationer/Ernaering-og-kostvaner
Protein requirement for the elderly
• Recommended: 15-20 % of energy intake (NNR-2012) or 1.1-1.3 g/kg/day
• Insufficient supply of protein will lead to loss of muscle mass and -function, that further enhances the risk of mortality and hospitalization, lowers quality of life, and prolongs reconvalecense
• Still, elderly people (+65) is a diverse group with different nutritional needs that must be taken into consideration when planning the diet:• Healthy, with normal activity, weight and appetite or
• Frail, sarcopenic with low appetite and declining functional status
https://kosthåndbogen.dk/content/energi-og-proteinbehov-hos-ældre
Special attention for patients at risk of disease-related malnutrition
• Unintended weightloss as a consequence of disease-induced altered metabolism and/or medical/surgical treatment affecting appetite, mood, gutmobility, taste, foodpreferences, ability to swallow and chew food etc.
• During acute illness and injury, protein turover is enhanced, causing unwanted loss of lean body mass, if not counteracted by increased protein intake and muscle stimulation.
• Protein requirement is increased to aprox. 1,2-2,0 g/kg bodyweight depending on the severity of the disease/injury.
• About 30-40 % of hospitalized patients are reported to be at risk of disease-related malnutrition.
Rasmussen H et al. Clin Nutr. 2004 Oct;23(5):1009-15Sorensen et al. 2008. Clin Nutr. 2008 Jun;27(3):340-9
Protein qualityAmino Acid profile and digestibility
Where do EAA come from?
• Nitrogen is recycled just as carbon and oxygen are recycled in nature
• Various microorganisms have the appropriate enzymes to convert elemental nitrogen from the air into ammonia, nitrate, and nitrites.
• Green plants use the ammonia or nitrate as raw materials for the synthesis of amino acids and proteins.
• Animals and humans in turn use the plants to supply nitrogen to make amino acids and proteins.
• Finally, the nitrogen cycle is completed when plant and animal residues are decayed by microorganisms back to nitrates, nitrites and finally nitrogen gas for the air.
Distribution of essential amino acids in common foods
Egg Beef Milk Soya Potato Rice Maize Wheat Cassava Yam UK diet Indian diet
Lys 139 203 158 144 121 86 58 57 92 91 140 87
Tryp 293 213 417 217 240 224 117 217 192 213 211 293
Threo 223 202 191 191 167 153 157 127 115 157 177 143
SAA 225 182 164 114 131 176 132 203 124 125 174 182
BCAA 168 144 151 136 120 146 177 122 79 116 143 132
TAAA 301 275 271 281 243 305 314 306 135 265 311 317
Lys, lysine; Tryp, tryptophan; Threo, threonine; SAA, sulphur amino acids (methionine + cysteine); BCAA, branched-chain amino acids (leucine, isoleucine, valin); TAAA, total aromatic amino acids (phenylalanine, tyrosine), cysteine and tyrosine are considered conditionally essential.
From WHO technical Report Series 935: Protein and amino acids requirements in human nutrition
Digestibility
• Describes the extent to which a protein/amino acid is absorbed
• Most studies are based on animal studies (mostly rats) after feeding a single protein source, and the measuring the amount of nitrogen in fecal or urinary loss
• In plant proteins, the amount of fiber in the plants cell walls will negatively affect the digestibility, since the undigested fiber will carry a small percentage of the protein through the digestive system.
• Food preparation techniques like cooking, sprouting and soaking can positively affect digestibility
• This is assumedly linked to the activation of plant enzymes that begin protein breakdown and the destruction of phytates and trypsin inhibitors that can limit digestion
Davis B and Melina V. Becoming vegan – the comprehensive edition, 2014.
Measuring protein quality – PDCAAS and DIAASBoth methods are based on the same basic calculation formula:Limiting amino acid (mg/g)/Amino Acid requirement (mg/g) x digestibility
PDCAAS: Protein Digestibility Corrected Amino Acid Score• Recommended ”preferred best” method by FAO/WHO in
1989
• New: Based on human requirements (of a 2- to 5-year-old child), as opposed to former methods based on animal needs (rats).
• Fecal digestibility of the protein (based on animal studies)
• Values >1 are not used, but extrapolated (truncated) to 1
• Good quality protein defined as proteins with a PDCAAS value of 1.0
DIAAS: Digestible Indispensable Amino Acid Score• In 2013 FAO proposed changing to DIAAS as best method
• Ileal digestibility of the single AA, based on preferably human models, secondary pig or rat models.
• Ileal digestibility gives a more accurate measure of the amounts of the AA absorbed by the body and the protein’s contribution to human AA and nitrogen requirements
• Values above 100% should not be truncated exceptwhere calculating DIAAS for protein or AA intakes for mixed diets or sole source foods.
• Currently available data are insufficient to support the application in practice of true ileal AA digestibility in the calculation of DIAAS.
FAO Food and Nutrition Paper 92: “Dietary protein quality evaluation in human nutrition”. Report of an FAO Expert consultation, 31 March – 2 april 2011, Auckland, New Zealand. Food and agriculture organization of the United Nations, Rome 2013.
Are animal protein superior to plant protein?Depends on what you are looking for:
• With DIAAS and PDCAAS, all whole food plant protein have a lower score than animal protein, especially related to the lower digestibility
• Whey protein seems to be superior for rapid gaining of muscle mass when compared with soy protein. But is fast always better for health? Whey contains a high level of the branched chain amino acid (BCAA) leucine. Leucine turns on a receptor on the muscle cells called mTOR, that promotes muscle growth. But mTOR may also seem to promote diabetes and cancer.
• One single source of protein (a single food item) can never constitute a healthy DIET on its own. Neither a diet based on beef alone or a diet based on wheat alone. Essential nutrients will evidently be missing in the diet. You will get all IAA on the beef diet, but miss vitamins, minerals and fibers from plant sources. A diet consisting only of wheat will be short in lysine, and also miss some vitamins and minerals too.
• What really makes sense is to focus on a mixed diet with a variety of food sources.
• A diet of mixed plantfoods with grains, legumes, vegetables, fruits, nuts and seeds will provide above RDA of all essential AA, vitamins (- vit. B12 and D), minerals, + fibers and phytonutrients, as long as the calorie intake is sufficient to sustain a healthy body weight.
• Studies on people living to the oldest ages and still living healthy, active lives (Blue Zones), reveals a diet of aprox. 95-100 % plant-based diet. A low or absent intake of animal protein seems to be of no hinderance for staying active and healthy throughout the lifespan.
Berrazaga I et al. Nutrients 2019, 11(8): 1825. Yoon M. Nutrients 2016, 8(7): 405. Hua H et al. J Hematology and oncology 2019, vol. 12, 19.
Complementary proteins?
• Introduced in 1970 by Francis Moore Lappe in her book “Diet for a small planet”.
• The idea was to combine various plant protein sources in every meal to ”make” a complete protein, mostly by mixing legumes (lysine) with grains (methionine).
• Research have shown this is not true, we need a variety over the course of the day or a few days.
• Children may benefit from eating legumes and grain together, particularly if total protein intake is marginal, although not essential at each meal.
• Still, in many cultures mixing legumes and grains are an integrated part of the mealculture, eg. Tofu and rice in Asia, lentils and teff in Ethiopia, lentils (dahl) with millet, rice or bread in Nepal and India, black or pinto beans with maize or quinoa in Mexico/south America and peanutbutter sandwich in North America
• Vegans do need to consider getting a mix of plant proteins in their diet to secure sufficient intake of all IAA
Davis B and Melina V. Becoming vegan – the comprehensive edition, 2014. Milward DJ. Proc Nutr. Soc. 1999;58:249-60.
Is it possible to get enough protein on a purely plantbased diet?
• There are no studys on nitrogen balance or protein synthesis in vegans
• A 2015 report from EPIC-Oxford study analyzed the dietary intakes and blood levels of amino acids in variousdiet groups in adult men
• This study confirmed the idea that lysine is the limitingamino acid in vegan diets, with vegan men surpassing the RDA by the lowest amount – 9%. Methionine, the aminoacid of second most concern, surpassed the RDA at the next lowest level of 33%.
• In comparing blood levels of amino acids between diet groups, vegans had lower levels of lysine, methionine, tryptophan, and tyrosine, and higher levels of alanine and glycine. But all within or above the reference ranges given by the U.S. National Library of Medicine
• Lysine rich foods are legumes, peanuts, pumpkin seeds, quinoa, amaranth, buckwheat, pistachios
Schmidt JA et al. Plasma concentrations and intakes of amino acids in male meat-eaters, fish-eaters, vegetarians and vegans: a cross-sectional analysis in the EPIC-Oxford cohort. Eur J Clin Nutr. 2015 Sep 23.
Tabel: https://jacknorrisrd.com/category/protein/
