BIOLOGY UNIT 2: NUTRIENTS AND FOOD part II

Exercise: See the table of the kilocalories that contain different types of food and answer the following questions:

What do you think is the normal Kcal/100g average? 0-100 Kcal/100g 200-300 Kcal/100g 300-400 Kcal/100g

What types of food have the higher Kcal/100g? Why?

Would you recommend avoiding these completely in a diet to lose weight? Why?

What types of food have the lower Kcal/100g? Why?

Would you recommend avoiding these completely in a diet to gain weight? Why?

5. LECTURES AND EXERCISES

5.1 INSULIN AND OBESITY

Glucose is the blood sugar and the main source of energy for our cells. Its concentration in our blood is about 70 to 110 mg/dL. When we eat an excess of sugars, there is an excess of glucose

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in our blood. To decrease the blood sugar, our pancreas produces a hormone called insulin that decreases the blood glucose by producing glycogen that is stored in the muscles and liver for when it is needed but our body can not store much glycogen, so the excess of glucose is turned into fats that will be stored (an excess of insulin activates the formation and storage of fat). If it happens very often we will get fat (it can lead to obesity).

Processed food (muffins, biscuits…) and processed drinks (sodas, industrial juices) contain large amounts of sugars without fibre (see fibre and health and whole grains versus refined grains), causing an excess of blood sugar that drives the pancreas to produce large amounts of insulin that leads to obesity.

Fruits do not have an excess of sugars and contains fibre. The fibre produces a slower absorption of sugar from the digestive system to the blood, so the pancreas does not need to produce as much insulin, in these conditions, there is not an excess of insulin and some glucose is stored as glycogen and some glucose is used in the cells to obtain energy instead of being turned into fats and stored.

What causes the production of high amounts of insulin and why does an excess of insulin causes obesity as time passes?

What recommendations can you give to reduce the risk of obesity?

5.2 FIBRE AND HEALTH

Plant cell walls are made up of cellulose and small quantities of other substances, all this form what we call dietary fibre. When we eat plant-based food, we obtain fibre in our diet that is very important for our health because of the following reasons:

- It prevents obesity, first because we can not digest it, so we obtain zero Kcal, second because fibre absorbs a lot of water, it swells in our stomach and when the stomach is full you don’t feel hungry, and third the absorption of glucose in the digestive system goes slower when there is fibre, so large amounts of insulin are not produced in our body (it reduces the risk of obesity because an excess of insulin produce the transformation of glucose into fat and the storage of this fat).

- In developed countries people eat a lot of animal products (meat, eggs, milk…), so there is an excess of cholesterol in our diet that can lead to cardiovascular diseases. Fibre decreases the absorption of cholesterol in the digestive system (it reduces the risk of cardiovascular diseases).

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- As fibre absorbs more water the faeces are soft and move more easily through the intestine (it prevents constipation). As the faeces move more easily, the faeces are excreted more often, it prevents cancer because toxic substances don’t stay long in the digestive system.

In developed countries the amount of fibre in our diet is low because of the refined grains and the big intake of animal products in the diet. As we can expect, the diseases that fibre prevents are very common in developed countries.

Name all the diseases that can be prevented eating enough fibre in our diet.

Are these diseases very common in developed countries?

Is there enough fibre in the developed countries diet?

Give three reasons to explain the fact that fibre prevents obesity.

5.3 WHOLE GRAINS VERSUS REFINED GRAINS

The most common food in human diets are cereal grains such as rice, wheat, corn… these grains are plant seeds, also, named whole grains. Whole grains are made up of three parts: the bran, the germ and the endosperm.

The bran is the outer layer it contains much fibre and some minerals and vitamins, the endosperm contains mainly carbohydrates (starch) and the germ is rich in nutrients such as minerals, vitamins, essential fatty acids and phytochemicals (protective plant substances).

The food industry removes the germ so that the grain can be preserved longer and they can store

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the grains, and the bran is also removed to taste better. This industrial process of removing the germ and the bran is to refine the grain.

Refined grains are very poor in nutrients, most processed food contains refined grains that leads to a deficiency in vitamins, minerals and other nutrients.

The food industry refines grain, so, when you buy from the supermarket any processed food that contains wheat such as bread, biscuits, pasta ... You can see in the ingredients that it usually appears wheat starch or wheat flour (almidón de trigo o harina de trigo) and never whole wheat (trigo integral). By refining grains all processed foods from the food industry are deficient in vitamins and minerals and fibre (these nutrients were in the germ and bran that were removed).

Conclusion: It is recommended to take whole foods (with the bran and germ) for proper nutrition (provides minerals and vitamins because whole food means no refined food). Sometimes the food industry adds to these foods vitamins and minerals that have been lost in the industrial processing (refining). Example: breakfast cereals (you can see that in the ingredients it has included minerals and vitamins).

What are healthier, refined grains or whole grains? Why?

How can I know whether the cereal has been refined or not looking at the ingredients?

5.4 OMEGA 6 / OMEGA 3 RATIO

Certain omega-6 fatty acids have an inflammatory effect (an excess of inflammation promotes cancer, cardiovascular diseases ...), stimulate coagulation (an excess of clotting increases the likelihood of cardiovascular disease ...), stimulate the storage of fats and the formation of fat cells (both increase obesity), stimulate cell growth (in excess this promotes cancer), inhibit the immune system, while omega-3 fatty acids have contrary functions: anticoagulant, anti-inflammatory, to limit the production of fats, regulates cell division, helps the development of the nervous system, stimulates the immune system...

Omega-6 fatty acids Omega-3 fatty acidsStimulate coagulation Anticoagulant effectinflammatory effect anti-inflammatory effect

produce fats and the formation of fat cells limit production of fatsstimulate cell growth regulate cell division

inhibit the immune system stimulate the immune system

We need to have a similar amount in the body of both types of fatty acids to keep a good balance in these functions. In the past the humans had a balance of fats Omega-6 and Omega-3 (in a ratio of 1: 1), but nowadays, in developed countries, mainly, the ratio is about 20:1 (too much omega-6 fatty acids). This dramatic change in the ratio of omega-6 and omega-3 fats consumed in the diet, perhaps more than any other dietary factor, has contributed to the epidemic of modern disease. Elevated omega-6 intake is associated with an increase in all inflammatory diseases – which is to say virtually all diseases. The list includes (but isn’t limited to): cardiovascular disease, type 2 diabetes, obesity, metabolic syndrome,

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irritable bowel syndrome & inflammatory bowel disease, macular degeneration, rheumatoid arthritis, asthma, cancer, psychiatric disorders, autoimmune diseases… Big Pharma (the pharmaceutical industry) is well aware of the effect of omega-6 on inflammation. In fact, over-the-counter and prescription NSAIDs (ibuprofen, aspirin, etc.) work by reducing the formation of inflammatory compounds derived from omega-6 fatty acids. (The same effect could be achieved by simply limiting dietary intake of omega-6, but of course the drug companies don’t want you to know that. Less profit for them.)

The omega-3 fatty acids are present mainly in grass and in fatty fish like salmon, sardines or mackerel and omega-6 fatty acids are present mainly in cereal grains, especially corn. Our ancestors subsisted on a diet that had a balance of fats Omega-6 and Omega-3 (in a ratio of 1: 1). The amount of Omega-6 fatty acids in the western diet increased substantially when refined vegetable oils (corn, soybeans, sunflower) began to form part of the diet and when livestock began to be fed with food rich in omega-6 (corn and other cereal grains instead of the natural livestock food such as grass). So the modern vegetable oil industry and the increased use of cereal grains as feed for domestic livestock have caused that we are eating oils and animal products (meat, eggs and milk) with very excessive amounts of omega-6 fatty acids. Nowadays, the current western diet is very high in Omega-6 fats and the ratio of Omega-6: Omega-3 fatty acids in people are about 20: 1. These excessive levels of omega-6 compared with omega-3, increase the risk of various diseases. The risks of this high concentration or consumption of omega-6 are associated with cardiovascular disease, arthritis, osteoporosis, swelling, mood changes (depression), obesity and cancer. Modern medicines are made to treat and control the harmful effects of omega-6 fatty acids such as decrease inflammation caused by excess omega-6 (aspirin, ibuprofen, cortisone are anti-inflammatory drugs).

Why do we have an excess of omega 6 fatty acids?

What do you recommend to have a good balance of omega-6 / omega-3 fatty acids in your diet?

What diseases are related to an excess of omega-6 fatty acids? Are they the most common chronic diseases of the developed countries?

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5.5 TRANS FATS

They are not present in natural food, but the food industry produces them by hydrogenating vegetable oils (process requiring high temperature). It could also appear when the oil is reused several times (restaurants, especially fast food restaurants always have chips on their menus and they do not change the oil in the fryer, they just add more oil as it is spent). In the fryer the oil temperature is very high for so long that trans fats are formed (the oils we usually eat at restaurants and in many homes are rich in trans fats, as they have been manipulated at high temperatures). The food industry hydrogenates vegetable oils to make them solid, to increase their expiration date and to improve its flavor.

Trans fats are very harmful because they are related to cardiovascular diseases, cancer and brain development problems. In some countries, trans fats are prohibited and others only allowed if they are less than 2% of the total fat and in Spain there are no restrictions on its use.

Trans fats are abundant in many processed foods. A trick to know if a food contains trans fats

is to look at the ingredients if it is written: hydrogenated or partially hydrogenated vegetable fats or

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vegetable oils. Look at processed food in your house and check the ingredients to see if they contain trans fats. What food did you find that contain trans fats?

Why does the food industry hydrogenate vegetable fats/oils, if it is unhealthy for the consumer?

What would you recommend to avoid trans fats in the diet?

5.6 PROCESSED FOODS IS NOT HEALTHY

The food industry creates a large variety of different processed foods using the 3 same cheap ingredients: refined carbohydrates (sugars and starches) and cheap refined vegetable fats. Most foods have these 3 ingredients among the most abundant and others at least one or two of them. For example confectionery: biscuits, cookies, cakes, muffins... they have these ingredients listed first (the ingredients are listed in order of abundance): wheat flour (this is to say starch which is the main nutrient in cereals), sugar, vegetable fat and then other ingredients in very small quantities such as milk and additives (colourings, preservatives, antioxidants ...). In conclusion, if you eat a lot of processed food your diet will not be varied and balanced because they are made of the same ingredients and besides they are all refined (refined = very low nutritional quality).

Starch comes from refined grains (poor in nutrients such as fibre, vitamins and minerals) and together with the refined sugars will greatly raise blood glucose, producing significant elevations of insulin (no fibre in sugar and starch = fast absorption of glucose in the intestine).

Vegetable fats do not usually indicate what type of oil it contains. It will almost certainly be the cheapest oils such as corn or soybeans that have large amounts of omega-6 and besides they are refined.

With all the lectures you read, you can draw the following conclusions: processed food does not provide a varied diet (almost everything is done with the 3 same ingredients), refined (lower in nutrients and fibre), rich in omega-6, trans fats usually appear in processed food. This explains the obesity epidemic in developed countries because their ingredients provide many kilocalories and our bodies also produce high levels of insulin and omega-6 (these 3 characteristics –high Kcal, high sugars and high omega-6- have been seen to produce obesity).

Do you think that processed food is healthy? Why?

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What do you think of soda and other sugary drinks?With all the readings on refined foods, trans fats, excess omega-6, excess sugar, importance

of fibre and composition of refined foods, all this is too much information to explain to someone interested in eating much healthier. To summarize it in one sentence in a simple way for everyone to understand, what could you advise people to reduce in their diet to eat much healthier? And in one sentence too, what could you advise people to increase in their diet to eat much healthier?

5.7 COOKING METHODS AND HEALTH

High frying temperatures can produce toxic substances. In a fryer temperature can exceed 300ºC, at this high temperature in oils, margarines or butter, small quantities of a toxic substance called acrolein can be formed. This is especially important when the same oil is reused many times (in many restaurants they never change the oil in the fryer, they just add more oil as it is getting depleted). Acroleins have been linked to an increased risk of lung and pancreatic cancer. The high temperatures when frying food, also alters some nutrients and it is also harder to digest the fats and proteins altered and consequently digestions become heavier.

Other high temperatures cooking methods are also grills and barbecues. In all of them (fryer, grill and barbecue) we can see black burnt pieces of food, these burnt food can contain acrolein and other carcinogenic substances such as benzopyrene and heterocyclic amines.

In conclusion, very high temperature produced in some cooking methods can produce toxic substances and alters food nutrients, for example it destroys vitamins. It is better not to eat burnt food and not to reuse the same oil several times when frying. Better cooking methods (less temperature) are boiling and steaming. Remember it is important to eat raw food everyday such as salads and fruits so vitamins and other nutrients are not altered.

Why we should not eat an excess of fried, grilled or barbecued food?

6. FOOD PRESERVATION

The fact that food goes bad and gets rotten is a natural process due mainly to the existence of microorganisms (fungi and bacteria) that grow in food, the atmospheric oxygen and enzymes present in the food itself can also alter food. Eliminating these microorganisms or stopping their action are ways of preserving food, both at home and in industry, so that we are able to store food for as long as possible, but food can not be preserved indefinitely and it is indicated in a expiration date label. The most common preservation methods are cooling, heating and the use of preservatives:

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- Cold preservation methods: Low temperatures reduce the action of enzymes and the action and growth of microorganisms, these methods are refrigeration where the temperature is only a few degrees above 0ºC and food can last for days, and freezing where the temperature is below zero and food can last for months.

- Heat preservation methods: Heat destroys the enzymes and kills the microorganisms in food, but it also destroys some nutrients such as vitamins. Two of these methods are UHT and pasteurisation. UHT (Ultra High Temperature) consists of heating food too 135ºC for a few seconds, this destroys all the microorganisms and pasteurisation consist of heating food to 80ºC for seconds, this kill most of the microorganisms.

- Food preservatives: Large quantities of sugar, oil or salt can help to preserve food by killing microorganisms. Microorganisms like all living beings can not live without water, sugar and salt dehydrate cells and oil doesn’t have any water. Acidc substances such as vinegar can kill microorganisms.

The industry uses many chemical substances called preservatives that are additives to kill microorganisms. There is also food which is preserved with smoke released by burning wood (smoke contains substances that kill microorganisms), this food is called smoked food (ahumados). Both of them, smoke and the additives called preservatives can be toxic in excess.

Exercises: 1) What are the 3 causes that make food to go bad?

2) If microorganisms can not live in olive oil and other oils because there is no water in oils, why do oils have a best before date label?

3) Why does most processed food contain antioxidant additives in their ingredients?

4) When is milk more nutritious, with or without heating it (pasteurisation or UHT)? Why?

Exercise: Bring to class processed food boxes or bags where we can see the nutritional label and the ingredients and answer the following questions:

Are sugar, vegetable oil (vegetable fat) and cereal grain (wheat, starch) listed as the most abundant ingredients? (¿Aparecen azúcares, grasas o aceites vegetales y cereales (harina, almidón) como los ingredientes más abundantes?)

These 3 ingredients are very cheap (they do not include olive oil that is more expensive) and all these ingredients are refined. Will it be healthy? Explain your answer.

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Do the processed food have much kilocalories (>400 Kcal/100g)?Do the processed foods have much sugar?

Do the processed food have a lot of saturated fat (>1/3) compared with monounsaturated and polyunsaturated fats?

7. FOOD RELATED ILLNESSES

Food related illnesses are those which are due to malnutrition or bad diet, as well as different forms of food poisoning.

Malnutrition

Malnutrition is caused by inadequate diet. Malnutrition may result from insufficient food (undernutrition) or excessive food (overnutrition) or because of the lack of some nutrient in the diet (deficiency diseases).

-Undernutrition: is common in poor countries, due to the lack of food.

-Overnutrition: is common in rich countries. Overnutrition and sedentarism together are responsible for the common chronic diseases in the rich countries such as obesity, diabetes, cardiovascular diseases, cancer… In rich countries we eat an excess of meat, milk, table salt, sugar, kilocalories and omega-6 fatty acids.

-Deficiency diseases: the most known deficiency diseases are anemia caused by the deficiency of iron, constipation caused by the deficiency of fibre, scurvy caused by the lack of vitamin C and rickets caused by the deficiency of vitamin D.

Food poisoning

Food poisoning may occur from eating food or drinking water contaminated with organisms that can produce a disease such as the bacteria that causes salmonelosis and other bacteria or viruses that can cause diarrhea.

Food poisoning may also occur from ingestion of food or water contaminated with toxic chemical substances, such as pesticides.

8. FOOD ADITIVES

Food additives are natural or artificial (synthetic) substances that become part of a food product when they are added during the processing or making of that food. Food additives are added to food to improve its taste, to preserve flavour or make it look more attractive and prevent it from spoiling. In the European Union (EU) all approved additives are identified by an E number.

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Although, the approved additives are generally recognized as safe for most people in the doses used, we still don’t know what effects many food additives can have on the body, especially synthetic additives. According to some scientists, excessive or indiscriminate use of certain additives can be damaging to your health.

Some food additives that are commonly used are:

- Colourings (colorantes, E-100-199): Make food look more attractive for the consumer. For example chlorophylls (E-140 and E-141) are natural green colourings, but some may cause problems such as tartracine, a synthetic yellow colouring used to make paella (it is advisable to use saffron instead of tartracine for making paellas).

- Preservatives (conservantes, E-200-299): Prolong the life of food by preventing microbial growth. Many of them can damage to your health for example benzoates (E-210-218), nitrates (E-249-252) and sulphites (E-220-228) are unhealthy preservatives.

- Antioxidants (antioxidantes, E-300-399): Prevent oxidative changes in food. Oxygen can destroy some vitamins, turn brown apples or potatoes and turn rancid fats and oils. For example vitamins C (E-300-304) and E (E-306-309) are antioxidants, but other antioxidants such BHA (E-320) and BHT (E-321) are synthetic antioxidants that can damage to your health.

- Flavour enhancers (potenciadores del sabor, E-600-699): Improve the flavour of food. The most commonly used is monosodium glutamate (glutamato monosódico, E-621) a synthetic flavour enhancer that may cause problems.

- Sweeteners (edulcorantes, E-900-999): Give food a sweet taste, they may be sugar or artificial sweeteners; the latter are used in diet food and drinks. For example aspartame, acesulfame K, sucralose, saccharine… and they may cause problems.

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