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Transcript
BCH 282 Biochemistry of Nutrition Objectives: • To define nutrition and related words. • To identify nutritional requirements. • To understand Food pyramid. • To list types of nutrients and relation to health. • To define malnutrition and its classification. • To list main malnutrition problems. • To describe Obesity. • Nutrition is defined as the science of food and its relationship to health. Or, • The process of making use of food. • It is concerned primarily with the part played by nutrients in body growth, development and maintenance . • Dietetics is the practical application of the principles of nutrition; it includes the planning of meals for the well and the sick. • Good nutrition means “maintaining a nutritional status that enables us to grow well and enjoy good health.” • Nutrients are substances (specific dietary constituents) that are crucial for human life, growth & well-being. • Macronutrients (carbohydrates, lipids, proteins & water) are needed for energy and cell multiplication & repair. • Micronutrients are trace elements & vitamins, which are essential for metabolic processes. CLASSIFICATION OF FOODS • Classification by origin: - Foods of animal origin - Foods of vegetable origin • Classification by chemical composition: - Proteins – – – – Fats Carbohydrates Vitamins Minerals CLASSIFICATION BY PREDOMINANT FUNCTION • Body building foods: • -meat, milk, poultry, fish, eggs, pulses etc • Energy giving foods: • -cereals, sugars, fats, oils etc. • Protective foods: • -vegetables, fruits, milk, etc • Community Nutrition: Identification of nutritional needs of population groups and available resources. • Nutritional Epidemiology: It is the investigation of the relationship between diet and disease. Nutritional requirements Recommended Dietary Allowances (RDA): The level of nutrients considered to be adequate to meet the nutritional needs of all healthy persons. Knowledge of RDA is necessary to: • Assess the nutritional adequacy of diets for growth of infants, children and adolescents. • Maintain health in adults of both sexes and during pregnancy and lactation. The adequate diet & Food Pyramids Food Group System: • Classifies food according to similarity in nutrient content. • Foods placed in each group have a high nutrient density. Daily Food guide with Nutrient Pattern and Recommended Quantity. Group Milk and Cheese Key Nutrients Calcium, Protein Phosphorus, riboflavin Meats, poultry, fish, beans Protein, Iron Niacin, Thiamin Red meat -> Zinc Egg yolk and liver -> Vitamin A Dry beans and Nuts -> Magnesium Quantity Comments 3 cups for children 4 cups for teenagers 2 cups for adults Low-fat milk products have generally all the same nutrient content, however they are lower in calories and vitamin A. 2 servings Serving size: 2-3 ounces 1 ounce of meat = 1 egg or ½ cup cooked beans 1 ounce = 30 gm Legumes and nuts has a lower biological value than meat. They can be combined with animal or grain products to increase protein quality. Cholesterol and vitamin B12 are found only in animal sources. Food Pyramid Lessons from Food Pyramid: 1. Maintain a healthy weight. Studies show that the healthiest range for body weight is when the body mass index (BMI) is about 17 to 22. 2. Eat good fats and avoid bad fats. • • • • • Good fats are the oils found in nuts, seeds, grains and fish. They are high in the unsaturated fats necessary for good health. Good fats should contribute 30 to 45% of the total fat. Avoid saturated fats (animal fats and tropical oils e.g. coconut) to minimize the risk of heart disease. Trans-saturated fats are mainly found in margarines and commercial baked foods. 3. Eat whole-grain carbohydrates. Why? • whole-grain are more nutritious than refined carbohydrates • Being more slowly digested • Place less stress on pancreatic insulin production. • Sources of whole grain carbohydrates include whole meal bread, whole wheat, brown rice. • Avoid white bread, baked goods and pasta made with white flour. 4. Avoid red meat as a protein source and emphasize plant proteins. • Red meat consumption is linked to a variety of chronic diseases & increases the risk of hip fracture. • Animal proteins are usually packaged with saturated fat. 5. Eat plenty of vegetables and fruits. • Potatoes are not included as a vegetable. • Dark green leafy vegetables, and fruit are clearly beneficial. • A diet high in fruits and vegetables lowers blood pressure and cholesterol and reduces the risk of cancer. 6. Take a multivitamin daily. • This recommendation is insurance against any inadvertent deficiencies. Mediterranean Pyramid Main types of Nutrients Energy Supplying Nutrients: • Protein • Lipids • Carbohydrates Non-Energy Supplying Nutrients: • Vitamins • Minerals • Water PROTEINS • Proteins are complex organic nitrogenous compounds. • They also contain sulfur and in some cases phosphorous and iron. • Proteins are made of monomers called amino acids. • There are about 20 different aminoacids which are found in human body. • Of this 8-9 aa are termed “essential” as they are not synthesized in human body and must be obtained from dietary proteins. Protein Needs: • Adults: 0.8 gm/kg body weight per day • Excess protein is not used to build more muscle – If the body needs energy, the extra amino acids are used for energy – If the body does not need energy, the extra amino acids can be converted to fat and stored. Sources: • Complete proteins have all essential amino acids (animal sources) • Incomplete proteins lack one or more essential amino acids (plant sources) Functions of Proteins • Body building • Repair and maintenance of body tissues • Maintenance of osmotic pressure • Synthesis of bioactive substances and other vital molecules e.g. immunoglobulins Lipids • • Lipids include cholesterol and triglycerides Fat is necessary for health Functions 1. Main source of energy (9Kcal/g). 2. Spare protein. 3. Adipose tissue holds the body organs and nerves in place. 4. Maintain body temperature. 5. Transportation of fat soluble vitamins. Classification • Saturated fat: – Animal foods generally are rich sources – Palm and coconut oil also are rich sources • Monounsaturated fat – Olives, peanuts, and canola oil are rich sources • Polyunsaturated fat – Corn, sunflower, cotton seed, and nut oils are rich sources • Hydrogenated fat Hydrogenated fat • Hydrogenation process hardens liquid oils into more solid margarine. – It makes unsaturated fat in oil more saturated – Also it produces an unhealthy type of fat called “trans fatty acid” • Saturated fat and trans fatty acids may be harmful to health • Baked products and fried foods are often made with hydrogenated fats Cholesterol • Cholesterol is necessary for cell membranes and the production of vitamin D, bile, and certain hormones • It is found only in animal foods • High blood cholesterol levels are associated with increased risk of heart disease Fats yield fatty acids and glycerol on hydrolysis • Fatty acid content of different fats ( in per cent) • • • • • • • • • • Fats Saturated Monounsaturated Polyunsaturated fatty acids fatty acids fatty acids Coconut oil Palm oil Cotton seed oil Groundnut oil Sunflower oil Corn oil Soya bean oil Butter 92 46 25 19 8 8 14 60 6 44 25 50 27 27 24 37 2 10 50 31 65 65 62 3 Fat requirements • The WHO Expert committee on Prevention of Coronary Heart Disease has recommended only 20 to 30 per cent of total dietary energy to be provided by fats. (<30%) • At least 50 per cent of fat intake should consist of vegetable oils rich in essential fatty acids. Carbohydrates Functions: 1. Carbohydrate is the main source of energy, providing 4 Kcals per one gram 2. Carbohydrate is essential for the synthesis of certain non-essential amino acids. 3. Necessary for normal fat metabolism. 4. Necessary for integrity of nerve cells. 5. Lactose allow growth of beneficial bacteria in the intestine. 6. Important for normal elimination (excretion); fibers Recommended carbohydrate intake is 55% to 65% of calories, primarily from starchy foods Classification of Carbohydrates 1. 2. 3. 4. Monosaccharides: glucose &fractose Disaccharides: Sucrose (G + F) Oligosaccharides (3-10). Polysaccharides (11-1000) a-Indigestable e.g. cellulose b-partially digestable e.g.raffinose c-Digestable e.g. starch The inability of the body to metabolize carbohydrates properly =DM Fiber • Indigestible plant material e.g. cellulose • Dietary fiber is mainly non-starch polysaccharide • It is found in vegetables, fruits and grains. • Soluble fiber swells or dissolves in water – Rich sources include apples, bananas, citrus fruits, carrots • Importance: – Reduces cholesterol absorption – Slows absorption of glucose Fiber • Insoluble fiber remains unchanged in water – Rich food sources include brown rice, wheat bran, and whole grain products • Importance: • High fiber diet reduces the risk of heart disease, diabetes type II, diverticulosis, hemorrhoids, constipation, and possibly colorectal cancer * Refined foods lose fiber-rich parts during processing Non-Energy Supplying Nutrients • Vitamins • Minerals • Water Vitamins • Regulate growth, • maintain tissues, and • help carbohydrates, proteins, and fats release energy • Provide no calories (energy) • Needed in very small amounts Classes of Vitamins • Water Soluble: 8 different B vitamins and vitamin C • Fat Soluble: Vitamins A, D, E, and K • Most healthy people do not need supplements; vitamins can be obtained by eating a variety of foods – Supplementation can increase the risk of consuming toxic high levels Fat soluble vitamins Vitamin A • «Vitamin A» covers both: – a pre-formed vitamin, retinol, and – a pro-vitamin, beta carotene, which is converted to retinol in the intestinal mucosa. Sources: – Retinol in liver, code liver oil & eggs (animal sources) – Beta carotene: Coloured plants e.g. carrot, mango, apricot, pumpkin,….. (plant sources) VITAMIN Sources: • liver • milk • eggs • spinach • carrots • tomatoes • butter A Functions of Vitamin A • It is essential for normal vision. • It is necessary for maintaining the integrity and the normal functioning of glandular and epithelial tissue which lines intestinal, respiratory and urinary tracts as well as the skin and eyes. • It supports growth, especially skeletal growth • It may protect against some epithelial cancers such as bronchial cancers. Vitamin D • The nutritionally important forms of Vitamin D in man are: – Calciferol (Vitamin D2) and – Cholecalciferol (Vitamin D3) • Sources: Present in egg yolk + natural (ultraviolet rays in sunlight). VITAMIN • • • • contains in: liver caviar butter D Functions of vitamin D • Intestine: Promotes intestinal absorption of calcium and phosphorus • Bone: Stimulates normal mineralization, Enhances bone reabsorption, Affects collagen maturation • Kidney: Increases tubular reabsorption of phosphate Deficiency of vitamin D Deficiency of vitamin D leads to: • Rickets in children • Osteomalacia in adults Vitamin E • Antioxidant- Protects RBCs from haemolysis. • Present in wheat germ and green leafy vegetables Vitamin K • Important for blood coagulation • Present in leaves of plants + natural (flora). • Deficiency causes haemorrhagic manifestations. VITAMIN contains in: • liver • corn • eggs • vegetable oils E Water soluble vitamins Thiamine (B1) • Function: essential for the utilization of carbohydrates. • Present in brewer yeast, beans and legumes. • Deficiency: Beri-beri Deficiency of thiamine • Beriberi may occur in three main forms: – peripheral neuritis, – cardiac beriberi, – infantile beriberi, signs of peripheral neuropathy.