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Chapter 6

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Biomedical Physio & Kines
BPK 140
Michael Walsh

1 KIN 140 Section 6 Dr Mike Walsh NUTRITION In the section on chronic diseases, the major preventive actions always included diet, exercise, and weight control.As such the next few lectures will encompass these effective preventative measures to enhance the health and wellness of an individual or a population. Certainly we recognize that eating is a homeostatic drive. The trick is to eat the correct foods for proper nutrition. English sailors are sometimes called ‘Limeys’because they ate limes in the 1750 through 1800’s during long sailing voyages. Before the consumption of limes, thousands of sailors died from scurvy. Scurvy is perhaps the longest known nutritional deficiency malady dating back to Egyptian times. In 1747 on a long sailing voyage, 12 sailors contracted scurvy. Dr James Lind divided the sick into 6 groups of 2 and gave each group the normal sailors diet but also consumed a supplement that was different between the groups. The supplements consisted of either apple juice, an elixir, herbs and spices, water, vinegar, or citrus fruit. Only the 2 sailors receiving the citrus fruit made a quick and full recovery. The apple juice group showed some recovery and the other supplement groups did not improve. Dr Lind concluded that something in the citrus fruit was responsible for the sailor’s recovery from scurvy. It was not until the 20th century that the substance has been identified as vitamin C. Now we have a very strong association between nutrition and disease. A. Essential Nutrients There are about 45 essential nutrients required by your body. There are 4 macronutrients and the rest micronutrients. You require a large volume of macronutrients. Three of them provide energy and structural building blocks: proteins, fats, and carbohydrates. The fourth macronutrient is fibre. Micronutrients are vitamins and minerals. One more essential nutrient is water. B. Energy Each day you need energy to survive. Even when you are asleep you are using about 70 % of the energy you use when you are awake and at rest. Pumping blood and breathing require constant energy. Replacing every structure in your body requires energy: whether it is stomach epithelium every 2 days or red blood cells every 4 months, body parts need to be replaced. For nutrition, energy is measured in calories.Acalorie is a unit of heat used to express the energy value of food. One calorie represents the amount of heat necessary to increase the 2 temperature of one gram of water by one degree centigrade. Sometimes the term Calorie is used. This term with a capital “C” is equivalent to 1,000 calories (i.e., 1 kilocalorie or 1 kcal). The capital “C” Calories is often confusing. Furthermore, the textbook used the capital “c” definition with a small “c”. In these notes and for your exams the small “c” definition above will and should be used. You need about 2,000 kcal per day for normal functioning. Protein: 4 kcal/gm Fat: 9 kcal/gm Carbohydrates: 4 kcal/gm Alcohol: 7 kcal/gm The joule (J) is the scientific unit of energy, but it is less commonly used. 1 cal = 4.18 joules C. Macronutrients 1. Proteins The basic building block of proteins is an amino acid (aa). There are 20 different amino acids that combine in various ways to make billions of different proteins. Of these 20 aa, 9 are essential. That means you must obtain them in your diet because your body does not make them or does not make enough of them. The other 11 aa can be made in adequate amounts by your body providing one’s diet is healthy. When we consume proteins, our body breaks them down in the digestive tract to aa. These aa are absorbed and linked up again to make the proteins our body requires. The recommended daily consumption of protein is about 10-15 % of total calories. In North America, most diets consist of > 20 % protein. The exact amount of protein required is dependent on the quality of protein consumed. High quality (aka complete) proteins contain all the essential aa and in the correct amounts needed by the body. These include most animal proteins, eggs, cheese, and soy. Low quality (aka incomplete) proteins do not contain all the essential aa. They are missing one or more of the essential aa or do not have enough of one or more essential aa. This includes most plant proteins. This does not mean vegetarians are going to eventually suffer an aa deficiency. It is common to consume complementary proteins. In this case 2 different protein sources, with different limiting aa are consumed. If the diet is varied, then adequate dietary aa is not a problem. 3 2. Fats As discussed in the cardiovascular disease section, fats are made up of a glycerol and 3 fatty acids. The fatty acids can be completely saturated (with hydrogen) or unsaturated.A monounsaturated fat has 1 double bond and a polyunsaturated fat has more than 1 double bond. a. Saturated Fats Saturated fats are generally solid at room temperature. Red meat tends to contain relatively more saturated fat than plant fats with the exception of tropical oils. Beef fat: 50 % saturated fats Corn oil: 13 % Coconut oil: 86 % Tuna fat: 27 % b. Unsaturated Fats Unsaturated fats contain double bonds that lower the melting point making them liquid at room temperature. The essential fatty acids linoleic (omega-6: controversially heart healthy) and linolenic (omega-3: heart healthy) have double bonds 6 and 3 carbons from the methyl end. [Normally you start counting carbons from the carboxyl group. If you start from the methyl end, you use the term ‘omega’]. Common monounsaturated fats are olive and canola oils and common polyunsaturated fats are soybean, safflower, and corn oil. Health Associations with Fats Saturated fatty acids tend to increase LDL cholesterol. Trans fatty acids tend to increase LDL cholesterol. Omega-3 fatty acids tend to increase HDL. Monounsaturated fats tend to decrease LDL and not affect HDL. Polyunsaturated fats decrease LDL and HDL. Plant sterols (new Becel) can lower cholesterol in the blood. 4 3. Carbohydrates Carbohydrates are available in food in the simple form of mono and disaccharides and in complex form as starches. Sugar is a disaccharide of glucose and fructose. Mono and disaccharides are often called simple sugars. All carbohydrates can ultimately be converted to glucose. Every cell in you body uses glucose as an energy source. For CNS and red blood cells, glucose is their only source of fuel. Glucose levels in the blood normally range from 70-140 mg/100 mL (3.9-7.8 mM). Values that are too high can destroy tissue such as discussed in diabetes. If values are less than 20, you start hallucinating. Glucose can be stored as glycogen (large number of glucose molecules attached together) in the liver and muscles. The liver can release the glucose into the blood whereas the muscles cannot. It is also possible to convert glucose to fat but this only occurs after days of excessive carbohydrate intake. Foods rich in carbohydrates come almost entirely from plants with the exception of milk. Carbohydrates make up about 55-60 % of daily caloric intake. From a nutritional perspective it is better to consume complex rather than simple sugars. It is even better if the complex sugars undergo minimal refinements. It is common in our food industry to take grains such as wheat, oats, and rice and remove the outer high fibre layer of bran and the inner nutritious layer of germ, leaving just the middle starchy layer of endosperm. We do this even though most of the nutrients are in the outer and inner layer. Glycemic index The glycemic index is a comparison of how high blood sugar increases after ingestion of a food compared to the ingestion of 50-100 g of glucose. The increase in blood glucose when glucose is ingested is given a value of 100.Abaked potato gives a glycemic index of 85, brown rice 55, and beans 30. Diets with a high glycemic index reduce HDL and are associated with diabetes. 5 4. Fibre Fibre is made up of mostly by carbohydrates that cannot be digested and thus not available for energy generation. However, indirectly, bacteria in the colon do metabolize some of the fibre and produce short chain fatty acids that are absorbed and have caloric value. These short chain fatty acids are very heart healthy and reduce the incidence of colon cancer. Fibre is classified as soluble and insoluble. Soluble fibre forms a gel (e.g., pectin). Intake of soluble fibre (fruits, legumes, vegetables, and oat bran) lowers cholesterol and reduces the glycemic index of a food being digested and lowers appetite.
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