Physiology of nutrition

INCLUDES INFORMATION OF NUTRITIONS, BALANCED DIET AND DISORDER RELATED TO IMPROPER BALANCED DIET

1. Date: March 2, 2019

2. The objectives of good nutrition are to: Restore and provide energy Maintain and control physiological processes of the body. Promote growth and development. Repair the tissue damages. Prevent degeneration of the tissues. Minimize the impact of diseases on the body. Maintain immunity and fight infection.

3. Introduction Nutrition is the science that interprets the interaction of nutrients and other substances in food in relation to maintenance, growth, reproduction, health and disease of an organism . In general, a standard diet for an adult should contains: 50 % carbohydrate, 20% fat, 20% protein and 10% fibres. With advance of age, the fat and carbohydrate intake should be reduced and the fiber intake should be increased. The total caloric intake mainly depends on the individual’s ability to use and store energy and on the level of physical activity . The diet should contain all essential amino acids and minimum proteins that are required for tissue maintenance and repair. Vitamins and minerals are not energy sources, but are necessary for enzymatic reactions, growth and metabolisms.

4. Essential nutrition The essential nutrients in balanced diet are: Carbohydrates Proteins Fats Vitamins Minerals Carbohydrates: Major source of energy. 1 gm yields 4 kcal Excess consumption can lead to obesity

5. Types of carbohydrates Three classes of carbohydrates: Monosaccharides : Hexose ( glucose, fructose and galactose ) and pentose ( ribose and xylose) Disaccharides: sucrose, lactose, maltose Polysaccharides : starch and glycogen Many glucose units arranged in a complex way. Glycogen : polysaccharides of glucose found in animals, branching is less complex than starch and has only storage property . Starch : plants and contains two types of fibres: crude fibre and dietary fibre. Crude fibre consists mainly of cellulose and forms the structural frame work of plant cells.

6. Dietary fibre : carbohydrates (e.g. pectin, cellulose, hemicellulose) and some non- carbohydrate substances( e.g. lignin) Dietary fibre can be soluble and insoluble types: Soluble fibres bind with the bile acid and reduce the absorption of cholesterol from intestine. Also dissolve in water to form gel that slows the passage of digested food in large intestine , increasing reabsorption Insoluble fibre Contain cellulose, hemicellulose and lignins Facilitate water absorption from intestine and aid to the volume of feces . Enhance bowel emptying

7. Sources and functions of carbohydrate carbohydrates Sources Functions Monosaccharides Glucose Sugar, rice, bread, fruits, vegetables, honey, etc. Final form for tissue utilization Fructose Fruits and honey Converted to glucose by the liver Galactose Milk Lactose Converted to glucose by liver Disaccharides Sucrose Sugarcane, pineapple Converted to glucose in liver Lactose Milk Converted to glucose by the liver Maltose Germinating seeds Converted to glucose by liver Polysaccharides Starch Plants, rice, potato, wheat, cassava, corn Converted to glucose in liver

8. Fibers Soluble fibres Fruits, legume, grains Increases time of absorption of food Decrease absorption of cholesterol from intestine Insoluble fibres Vegetables, wheat bran Increases passage of intestinal content, prevent from constipation. EFFECTS OF DEFICIENCY OR EXCESS OF CARBOHYDRATES: Deficiency: Lysis of fats resulting increase in free fatty acids, and then ketosis. Decreased dietary fibre: carcinoma of the colon, diverticulosis, constipation, heart disease and gallbladder stone . Excess = O besity .

9. LIPIDS The main lipids in the diet are triglycerides(TG ). The different TG differ in structure depending on the degree of saturation, the length of the carbon chain and the presence or absence of essential fatty acids . Saturated and unsaturated fatty acid. Essential fatty acids are the highly unsaturated like linoleic acid, linolenic and arachidonic acid . Cholesterol: forms steroid hormones and vitamin D, component of cell membranes, formed in the liver acetyl-CoA.

10. Degree O f Saturation A fatty acid is saturated when every carbon atom in it has two hydrogen atoms attached. When in the carbon chain of fatty acids two adjacent carbon atoms are attached with a double bond as each C doesn’t have a hydrogen atom to connect with, they are called monounsaturated fatty acids (MUFA). When two or more double bonds occur in a fatty acid, they are called polyunsaturated fatty acids(PUFA) Fatty acids containing five or six double bonds are said to be highly unsaturated fatty acids (HUFA). PUFA is better than MUFA as MUFA may not retard atherosclerosis and hence it decreases membrane plasticity.

11. Length of the carbon chain Fatty acids in biological system usually contain an even number of carbon atoms, commonly between fourteen and twenty-four. Fatty acids with twelve carbon atoms in the chain or less are described as short fatty acids, and those with fourteen or more are termed as long chain fatty acids.

12. Presence of essential fatty acids Essential fatty acids are the highly unsaturated. They are linoleic acid, linolenic and arachidonic acid. Essential for the synthesis of eicosanoids like thromboxane, leukotrienes , prostacyclin and prostaglandins. They are involved in various physiological processes of the body like conception, induction of labor , abortion, immunity, inflammation and maintenance of vascular tone. As arachidonic acid can be synthesized in the body from linoleic and linolenic acids, it is a semi-essential fatty acid. Cholesterol: forms steroid hormones and vitamin D, component of cell membranes, formed in the liver acetyl-CoA.

13. Functions O f Dietary Fats Lipids provide energy. Breakdown of 1gm of fat yields 9.0 calories, whereas carbohydrate and proteins provide only 4.0 calories each. Lipids are essential component of cell membrane as they maintain fluidity and integrity. Vitamins A, D, E, and K are soluble in fat. Thus, fat transports these vitamins for their absorption from intestine. Palatability of food depends on quantity of fat in it. Gastric emptying greatly depends on the fat content of food eaten. More the fat, slower is the emptying. Essential fatty acids are essential for fromation of many eicosanoid compounds like prostaglandins , leukotrienes etc. Cholesterol is the primary source of steroid hormones. Subcutaneous fat acts as an insulator that play important role in temperature regulation. It prevents transfer heat between the body and the environment. Brown fat in children contribute to non-shivering thermogenesis. During starvation, fatty acids converted to ketone bodies supply energy. Thus, more the fat content , better is the ability to sustain food-deprivation. Exert a cushioning effect and protect the internal organs.

14. Daily requirement and sources Average I ndian diet contains approx. 25% fat (especially linoleic acid). American and Africans consume about 40-45% and 10% fat respectively in diet. The major lipid in the diet is TG Cholesterol : egg yolk, meat and liver. Saturated fats (butyric, caproic , caprylic , lauric , palmitic , stearic and arachidic fatty acids) are present in butter, coconut oil, animal fat, vegetable oil and peanut oil. Unsaturated fats ( palmitoleic , oleic, linoleic, linolenic , arachidonic , eicosapentaenoic and docosahexaenoic fatty acids) are present in seed oils, soyabean , peanut oil and fish oil. After absorption from intestine, lipids are transported in the blood in four forms containing different proportion of TG, phospholipids, cholesterol and protein. Chylomicrons, containing about 85% TG VLDL LDL HDL

15. Diseases Associated with Excess Fat Consumption of excess fat leads to obesity. Acceleration of atherosclerosis, coronary heart disease(CHD), stroke, breast and prostate cancer, hypertension and diabetes are commonly obesity associated disorders. Serum TC levels below 200 mg/dl is considered normal. Though, only about 10% of the total plasma cholesterol is derived from diet , rest comes from liver. High LDL, VLDL and TG are harmful, whereas high HDL is good for health. Regular physical activities , practicing of yoga, cheerful mind and consumption of fish and vegetables in diet increases HDL and decreases VLDL. Mild to moderate alcohol consumption, especially red wine has been proved to be effective in increasing plasma HDL and reducing the incidence of coronary artery disease. Decreased calorie intake, decreased intake of unsaturated fat and increased consumption of PUFA is helpful in this regard.

16. PROTEINS Made up of amino acids. Usually, proteins contain about 16% Nitrogen. therefore, the food protein content, or the amount of protein loss in urine can be derived from estimating the nitrogen content in food or in urine. There essential and non-essential amino acids.

17. Classification of amino acids Essential amino acids Non-essential amino acids Lysine Aspartic acid Leucine Proline Isoleucine Alanine Phenylalanine Glycine Tryptophan Glutamic acid Methionine Serine Valine Tyrosine Threonine Cysteine Histidine Asparagine Arginine Glutamine

18. Functions of proteins Growth and development Synthetic functions Maintenance of pH Transport function Immunity functions Maintenance of osmotic pressure and filtration in capillaries. Storage Receptor Buffer Coagulation Enzymes

19. Daily requirement and sources The minimum intake of protein should be 1 g/Kg body weight. Proteins requirement is more in infants, children and adolescents and during pregnancy, lactation and recovery from diseases. Protein is derived from both animals and plants. Animal sources: meat, eggs, milk, poultry products and fish. Plant sources: nuts, beans, peas, cereals(maize and wheat) and dal. Animal proteins contain all the essential amino acids, and are referred to as grade I proteins. Plants proteins have limited amounts essential amino acids, and are referred to as grade II proteins.

20. VITAMINS Nomenclature for ‘Vitamins’ was coined by Casimir Funk in1912 for their ‘vital’ roles in the body. They are not energy sources but they play important role in metabolism. Acts as cofactor in many enzymatic reaction such as decarboxylation, carboxylation, etc. They act as oxidizing and reducing agents in oxido -reductive processes. Vitamins decreases the risk of various cancers by their antioxidant property e.g : β - carotene, vitamins C and E. Adequate vitamin E intake lowers the risk for coronory artery disease.

21. Type of Vitamins A. Water – soluble vitamins B. Fat- soluble Vitamins Thiamine ( vit . B1)- Beri -beri ( neurological and mental disturbance). Vitamin A( Retinal, retinol, retinoic acid) Riboflavin( Vit . B2)- glossitis ( cheilosis , soreness of the tongue, redness and burning sensation in eye, dermitits Vitamin D( Antirachitic factors, cholecalciferol , ergocalciferol , calcitriol ) Niacin ( Vit . B3)- pellagra( dermititis , diarrhoea, dementia), glossitis , mental disorder with polyneuropathy Vitamin E ( Tocopherol , anti- sterility factor) Pantothenic acid ( Vit B5)- dermititis , Enteritis, alopecia, adrenal insufficiency. Vitamin K ( Antihemorrahagic factor) Pyridoxine (Vit.B6)- convulsions, hyperirritability, dizziness and vomiting Colbamin ( Vit . B12)- pernicious anemia Folic acid ( Folate )- sprue , megaloblastic anaemia, sterility, low birth weight babies. Biotin (Vitamin H)- dermitis,enteritis Ascorbic acid ( Vit C)- scurvy

22. Vitamins deficiency can arise due to: Inadequate intake Impaired absorption Impaired metabolism Increased requirement( as in adolescence, pregnancy, lactation) Increased loss

23. VITAMIN A Functions in the body in three forms: retinol, retinal and retinoic acid. Animal sources: liver, egg yolk, fish, fish liver oil( cod liver oil, halibut liver oil) and cream of milk. Plant sources: Main plant sources are carrots, spinach, tomatoes, broccoli, green peas, mangoes, ripe papaya and sweet potato. The main plant source of vitamin A is carotenoid, which is the precursor of this vitamin. Daily requirement: 750-900 mg of retinol to adult, in lactating mothers, requirement is 50% more. 1 IU is 0.3 µg of retinol and 0.6 µg of β - carotene. Adult male and female require 3000 IU per day.

24. Function of Vitamin A: Role in Vision Epithelial cell function On bone and teeth formation On growth On reproduction Prevention of stress dysfunction On immunity

25. Vitamin A dysfunction Vitamin A deficiency: early and common features of vitamin A deficiency is night blindness, also called nyctalopia . Bitot’s spots appear on the conjunctiva and conjunctiva becomes dry and rough ( xerosis of conjunctiva or xerophthalmia ). The cornea becomes dry and opaque and finally degenerates( keratomalcia ). Vitamin A toxicity: Excess of vitamin A causes headache, drowsiness, nausea, dry skin, hair loss and diarrhoea. In infants, loss of appetite, weight loss, scaly dermatitis and bone pain and in women, menstrual irregularities

26. Vitamin D: Daily requirement: 100 IU in adults [ 1 IU= 2.5µg] Infants and children, and pregnant and lactating mothers need about 220 IU per day Plays important role in calcium metabolism Deficiency : rickets in children and osteomalacia in adults Hypervitaminosis D: anorexia, lassitude, constipation and polyuria. In chronic case, urinary lithiasis and metastatic calcification. Vitamin E: Daily requirement: For children: 10-15 IU per day For adults: 20- 25 IU per day 1 mg of α tocopherol is 1.49 IU of vitamin E Function: most potent antioxidant,anti -sterility, cofactors in electron transport in cytochrome chain. Deficiency : Hemolysis In infants, retinal damage and retrolental fibroplasia occur. Decreased immunity, degeneration and increased vulnerability to malignancies.

27. Vitamin K: Total daily dietary intake is estimated at 200-500mg Functions: Helps in physiological activity of II , VII, IX and X clotting factors by γ carboxylation of their glutamate residue, these are called vitamin K dependent clotting factors. Deficiency : clotting disorder Vitamin C: Daily requirement: Infants: 30 mg Children: 50mg Adolescence: 75 mg Adults: 100 mg Pregnant: 150mg Major sources : citrus fruits and vegetables Functions: Hasten oxidation- reduction reactions Collagen synthesis Conversion of tyrosine to noradrenaline, tryptophan to serotonin Smooth activity of fibroblast and osteoblast Anti-oxidant Converts folic to the folinic acid for its absorption Promotes formation of ferritin Helps in synthesis of carnitine It acts as a coenzyme for cathepsin and hepatic esterase

28. MINERALS Contains some 50 minerals which serve specific function in the body. Important minerals include: calcium, phosphorous, iron , sodium, potassium and magnesium Less quantity required: I, Zn, M n , Cu, Co and F. Zinc: Present is present in insulin and in many enzyme. Deficiency: skin ulcers, depress immune response and hypogonadal dwarfism. Copper: Forms ceruloplasmin by combining with α -globulin Deficiency: anaemia, changes in ossification and increase cholesterol. Minerals toxicity: Haemochromatosis Brain damage by excess copper.

29. Water It is the medium in which most of the chemical activities takes place in the body. More than 70% of the body wt. is imply because of the water it has. Loss of up to 10% body water=extremely tired and fatigue. More than 20% loss= may death.

30. BALANCED DIET A diet which contains types of food in such quantities and proportions that the need for energy, proteins, fats, carbohydrates, vitamins and minerals is adequate met for maintaining health, is called balanced diet Daily requirements of different types of food in an adult. Green vegetables=240gm Sugar=60gm Other vegetables=150gm Pulses=90gm Cereals=150gm Rice = 270gm Oil & fat = 60gm Milk = 120gm If the diet is deficient in any of these nutrients, malnutrition results and individual might suffer from physical and mental growth retardation.

31. FOOD ITEM CHILDREN( EITHER SEX) REFERENCE MAN REFERENCE WOMAN 1-3 yrs 4-6 yrs 10-12 yrs Cereals 175 270 420 460 410 Pulses 35 35 45 40 40 Leafy vegetables 40 50 50 40 100 Other vegetables 20 30 50 60 40 Roots and tubers 10 10 30 50 50 Milk and milk products 300 250 250 150 100 Oil and fat 15 25 40 40 20 Sugar and jaggery 30 40 45 30 20 Balances diets according to age and sex ( all values in gram) (source: ICMR)

32. Principles of diet planning No food is perfect though most foods contain more than one nutrient. In general, mixed diet is likely to adequate in protein, vitamins and minerals. For formulating diet for any individual, balanced diet should be based on: Of the total calorie requirements, at least 50% should be provided by carbohydrates; 25-30% from proteins and 20-25 % from fats. It should be a fibre rich balanced diet Should be locally available Should be such that it can prepared easily. Should fit with the local food habits. Diet should be easily digestible and palatable.

33. Applied aspects: Deficiency diseases: Health is affected not only by diseases but also by an unbalanced food. Inadequate amount of food leads to insufficient nutrition, resulting Malnutrition. The level of malnutrition in India is among the highest in the world, as many as 5000 children die of malnutrition everyday. Mal nutrition is more marked in vulnerable section of the population i.e. pregnant women, nursing mothers, infants and children

34. Diseases due to energy deficiency It leads to so called protein energy malnutrition.(PEM) The real deficiency is that of food energy which is measured terms of ‘calorie’. PEM is, therefore referred to as protein caloric malnutrition (PCM). PCM is the commonest form of malnutrition in India. Causative factors of PCM An inadequate diet, both in quantity and quality; primarily due to poverty Infectious and parasitic diseases such as repeated diarrhoea and chest infection, worms infestation, measles. Poor environmental condition. Adverse cultural practices like premature termination of breast feeding ; use of over-diluted milk; late weaning of the child PCM may lead to permanent mental and physical disabilities in children who survive.

35. Most serious forms of PCM: Kwashiorkor: gross protein deficiency Characteristic features: Generalized oedema (oedematous malnutrition):fluid retention in ankle, feet, belly Swollen face ( moon like) Hair ( sparse, straight with loss of pigment. Generalized skin changes: Areas of skin pigmentation alternating with scaling Areas of decreased pigmentation MARASMUS: severe calorie malnutrition Characteristics features: Absence of oedema. Marked muscular wasting, ribs are conspicuously visible. Brittle (fragile) hair Small sunken face (monkey like) Severe growth retardation: Limbs are thin ( look like sticks) Absence of fat from the buttocks.

36. Different between kwashiorkor and marasmus Principal features kwashiorkor Marasmus Causative factor Gross protein deficiency Severe calorie malnutrition Wt. as percentage of normal 60-80% Below 60% oedema present Absent Muscular wasting Occasionally seen Severe Growth retardation(physical and mental less Severe Appetite poor Usually good Skin changes Depigmentation of skin all over the body Loose with loss of elasticty hair Sparse, straight, greyish or reddish Brittle (fragile) face Swollen. Moon like face Small sunken, monkey face diarrhoea Often present May be present anaemia present May be present Liver enlargement Frequently, secondary to ‘fatty liver’ absent age In second and third year of life Usually seen in infants less than one year

37. Preventive measures Health promotion/ health education Provision of specific protection (immunization) against infectious diseases. Early detection and treatment of diarrhoea, chest infections and PCM Rehabilitation of the suffers by providing follow-up care.

38. B. UNDERNUTRITION AND STARVATION Under nutrition and starvation lead to wasting of the body with marked loss of adipose tissue and of muscles . During starvation, even if no physical work is being done, approx. 1500 kcal will be needed daily . So as long as fat is available tissue protein is ‘spared ’. Cause : Insufficient food in the diet. Severe diseases of the GIT such as malabsorption syndrome. Infection and toxaemias. They reduce appetite or interfere with normal metabolism.

39. Body changes During starvation, even if no physical work is being done, approx. 1500 kcal will be needed daily. The major source of energy is the fat reserve and tissue proteins. So as long as fat is available tissue protein is ‘spared’. Death occurs after about 4 weeks, when the body weight is reduced by 50%.

40. The major effects of under nutrition and starvation. Blood sugar : steady almost till the to the end. Body fat : Free fatty acids provide energy for muscles and favour to brain get continuous glucose supply. ketogenesis Tissue proteins : The brain and heart lose only 3% of their bulk; muscles, liver and spleen lose 30, 55 and 70% respectively. This is controlled through the action of adrenal cortex. Amino acids pool maintain the structure and so functional efficiency, to preserve normal sugar level. In first week, nitrogen excretion approx. 10gm/day. Water : Intracellular water is decreased but in extra cellular it not reduce, relative excess accumulates producing oedema. Water retention is promoted by : low plasma protein, fall in tissue tension secondary to loss of fat. Failure of hormone and enzyme production: During prolonged starvation the synthesis of protein hormones and enzymes is reduced causing: Delayed puberty and amenorrhoea in girls Lost of libido and impotence in male Marked atrophy of the thyroid gland due to reduced secretion of ‘ thyrotropic ’ hormone. Diarrhoea due to reduced formation of digestive enzymes.