Nutrition and Metabolism

1. Nutrition and Metabolism OGUNGBEMI Stephen Idowu Department of Physiology, College of Medicine, University of Lagos, Lagos, Nigeria.

2. AIMS OF NUTRITION • Supply of balanced diet, vitamins, minerals and water to maintain health and well-being. • Supply of calories. • For growth, repair of worn out tissues and synthesis of cellular products.

3. CONSTITUENTS OF DIET • Carbohydrate • Protein • Lipids • Vitamins • Minerals and • Water

4. ENERGY CONTENT OF FOODSTUFFS • It is measured in calories • It can be determined: • Directly by bomb calorimeter • Indirectly by measuring oxygen consumption • The caloric value of foodstuffs when metabolised in the body are: • Carbohydrate - 4.1 Kcal/g • Fat – 9.3 Kcal/g and • Protein – 4.1 Kcal/g

5. Dietary Requirements of Food Stuffs • Dietary protein should not be less than 1 g/Kg body weight/day. • 1st class or animal proteins contain essential amino acids in the proportion similar to that required by the body. • 2nd class proteins are of plant origin and lack one or more of the essential amino acids.

7. Fat has a high store of energy because 1g gives 9.3 Kcals. Fat are classified as saturated and unsaturated fatty acids. • Dietary fat should be about 60 g/Kg body weight/day including the essential fatty acids: • Linoleic acid • Linolenic acid and • Arachidonic acid

8. Saturated fats are obtained from animal fat e.g. beef, pork, poultry, diary products like butter, cheese and chocolate. • Plant oils e.g. coconut oil, palm oil and cocoa butter. • Unsaturated fats monounsaturated e.g. groundnut oil and rapeseed oil. Polyunsaturated e.g. corn oil, sunflower oil, soyabean oil, fish oil.

9. Unsaturated fats reduce low density lipoprotein (LDL) but increase high density lipoprotein (HDL) which lowers serum cholesterol and is very beneficial to the cardiovascular, reproductive, endocrine and nervous systems. • Carbohydrates produces energy to keep and maintain the body systems. • Vitamins are essential dietary requirements necessary only in small amount which must be present before food can be adequately metabolised as well as for normal functioning of the tissues.

10. There are fat and water soluble vitamins. • Fat soluble vitamins are vitamins A, D, E and K. • Water soluble vitamins are vitamins B and C. • Vitamin A (aka retinol) produced from β carotene. • It can form retinal and has anti-oxidant properties. • It is found in vegetables (especially carrot), fish oil, fats and milk. • It is required for the synthesis of rhodopsin (retinal visual purple) and maintenance of epithelial surfaces.

11. Its deficiency results in night blindness as well as xerophthalmia (dry cornea). • Vitamin B complex is found in yeast, liver, germ layer of cereals. • Vitamin B1(or thiamine) is required by neural tissues and deficiency causes polyneuritis (beriberi) dry and wet, heart failure and oedema. • Vitamin B2 (or riboflavin) deficiency causes sore tongue, angular stomatitis.

12. Niacin or nicotinic acid deficiency causes diarrhoea, dermatitis and dementia. • Panthotenic acid is a component of co-enzyme A. • Pyridoxin is used for intermediary metabolism. • Vitamin B12(aka cyanocobalamin) is required for the maturation of red blood cells. • It requires intrinsic factors for its absorption from the stomach. • Its deficiency results in pernicious megaloblastic anaemia.

13. Folic acid is also required for red cell maturation, and its deficiency produces megaloblastic anaemia. • Vitamin C (aka ascorbic acid) is obtainable from citrus fruits (orange, tangerine, lime, lemon, currants and grape). • It is an antioxidant needed in many metabolic redox reactions. • It is required in collagen synthesis. • Its deficiency produces scurvy, loose and infected teeth and delayed wound healing.

14. Vitamin D is supplied from animal oils, fish oils, diary products required for calcium absorption, and bone formation. • Its deficiency results in rickets in infants or osteomalacia in adults. • Vitamin D3 is cholecalciferol, D2 (ergocalciferol), D3 is produced by the action of ultraviolent light on the skin which converts 7-dihydrocholecalciferol to cholecalciferol.

15. Cholecalciferol is hydroxylated in the liver to 25- cholecalciferol . • It is then converted in the kidney by 1 hydroxylase to 1, 25- dihydrocholecalciferol. • 1, 25- dihydrocholecalciferol (active form of vitamin D) promotes calcium absorption in guts with parathyroid hormone. • Vitamin K is obtained from green vegetables. • It is required for prothrombin synthesis.

16. Its deficiency results in haemorrhagic disorders. • Vitamin E (aka tocopherol) is obtained from vegetable oil, sunflower seed. • It likely supports gamatogenesis. • It prevents cell damage as an antioxidant. • Biotin is obtained from liver, kidney and yeasts part of enzyme systems. Its deficiency results in dematitis.

17. MINERALS SALTS • Sodium is supplied from common salt. It is universally present. • It is the main extracellular cation needed for generation and transmission of membrane potentials in nerves and muscles. • Deficiency is not likely. • But there can be sodium loss in cholera and diarrhoea and the consequence body and muscle weakness.

18. Calcium is obtained from dairy products and present in bones as CaCO3 and Ca3(PO4)2. • Absorption is influenced by vitamin D3. • There is increased requirement during growth, pregnancy, breast-feeding, bone repair and ageing • Deficiency leads to osteoporosis. • Iron is a key constituent of haemoglobin. • It is obtained from liver, bone marrow, snail, plantain and cereals.

19. Absorption is in ferrous state and requires gastric and ascorbic acids. • It combines with apoferritin in mucosal cells to form ferritin in upper intestine. • It is transported in the plasma as transferrin. • Potassium is found in most foods especially fruits, green vegetable, potash. • It is the main intracellular cation for impulses transmission in nerves and muscles. It lowers blood pressure

20. Phosphorous is present in most foods. • Forms phosphate to join calcium for bone and teeth formation. • Copper is an integral part of some enzyme systems in metabolic pathways. • Magnesium is required for intracellular reactions. • Its deficiency causes apathy and muscle weakness.

21. Manganese is found in nuts, dark leaves. • It supports proper growth and reproductive system. • It is a key part of antioxidant enzymes. • Zinc is obtained from seafood, grains. It is an antioxidant and a component of many enzymes. • Fluoride is found in seafood and helps for strong teeth, preventing dental decay. • Cobalt is an essential component of vitamin B12.

22. Sulphur is found in some protein and amino acids. It is a component of B1 (thiamine). • Chromium is found in brewers’ yeast. It may help to reduce rise in serum cholesterol. • Selenium is found in seafood. It may help to reduce incidence of hypertension.

23. METABOLISM • Energy metabolism comprises series of reaction in the body (catabolism and anabolism) eventually leading to: • Growth • Production of heat to maintain body temperature and • Supply of energy for the vital process in the body • It is distinguished from intermediary metabolism which are specific chemical reactions eventually leading to liberation of heat from the body

24. Basal metabolism is the metabolism at rest, which are required for: • Automatic muscular movement of the heart, respiratory organs and the guts. • Synthesis reactions in the tissues e.g. protein synthesis. • Maintenance of body temperature at 37°C.

25. Therefore the total metabolic rate of the body is the sum of that required for: • Basal metabolism • Occupational work • Recreation and • Feeding including specific dynamic action of foodstuffs.

26. Calorific Requirement For BMR in male = 1700 Kcal/day In female = 1400 Kcal/day + For work For recreation For feeding = Average total requirement in Male = 3000 Kcal/day Female = 2300 Kcal/day

27. Increased calorie intake is required under certain conditions such as in: • Children because they are growing • Adolescence when another burst of growth occurs • Pregnant and lactating mothers • Recovery from illness

28. The specific dynamic action is the increase in heat production above the basal level owing to the ingestion of food by a subject in the basal state. • The values are: • Proteins – 30% • Carbohydrates – 6% and • Fats – 4% • Protein sparer are carbohydrates and fats. • When they are present in substantial amount in ingested food relieve tissues of the necessity of using

29. proteins for the provision of energy for the body. • Proteins can then be used more for other processes like synthesis, growth, tissue repair. • Basal metabolic rate • It is the heat production of in complete physical and mental resting state, in post-absorptive phase i.e. 12 – 14 hours after the last meal.

30. Determination of BMR • Direct method by using the Atwater Rose-Benedict respiratory calorimeter but it is not widely used. • The indirect method by using the Benedict-Roth spirometer to determine oxygen consumption rate. • Principle • The rate of oxygen consumption can be calculated from the slope of the spirometer • tracing and converted to liters/hour.

31. The average caloric equivalent of oxygen is 4.83 kilocalories/liter at an average respiratory quotient (RQ) of 0.82 • The RQ for the individual nutrient are: • Carbohydrate = 1.0 • Fat = 0.7 and • Protein = 0.8 • On a mixed diet, the average rate RQ come to 0.82

32. Calculations • VO2 = oxygen consumption in liter/hour • Calorie equivalent of O2 = 4.83 kilocalories/liter • Therefore, rate of heat production = VO2 x 4.8 kilocalories/hour • Since basal metabolic rate BMR = VO2 x 4.8 (kilocalories/hour) / surface area, SA, (m²).

33. So BMR = Kcal/hr/m² • SA = 0.007184 X W (Kg)⁰˙⁴²⁵ X H (cm)⁰˙⁷²⁵ • In practice, the surface area is obtained from a normogramme from the values of height (cm) and weight of the subjects. • The prediction formula has a racial differences.

34. Average Values: • Reference man = 40 KCal/hr/m² • Reference woman = 37 KCal/hr/m² • Usually BMR is calculated for an individual and then expressed as ±% of that predicted for his / her sex. • Factors Influencing BMR • Age: BMR is higher in children (50 KCal/hr/m²) than adults and gradually decreases with age, because of their rapid growth and metabolic processes and smaller size.

35. Sex: BMR is greater in male (40 KCal/hr/m²) than in female (37 KCal/hr/m²). • Pregnancy causes increase in BMR due to increased mass of pregnancy structures and foetal metabolism. • Climate: BMR is slightly raised in cold regions (from increased thermogenesis) but slightly lowered in hot climate (due to heat absorbed from radiant energy).

36. Hunger may increase BMR, but starvation and malnutrition lowers it. • Caffeine, glucose, taurine, adrenaline, thyroxine, alcohol, sympathetic activation, exercise, ACTH/cortisol raise BMR. • Dinitrophenol, ouabin, lowers BMR. • Hormonal: hyperthyroidism, adrenal hyperfunction raise BMR.

37. Max O₂ consumption = 132.853 – (0.0769 x weight) – (0.3877 x age) + (6.315 x gender) – (3.2649 x time) – (0.1565 x HR) • Where weight is in pounds • Gender = 1 (male) and 0 (female) • Time taken in minutes to run 1069 m at peak speed • HR in b/min and • Age in years • Max MR = Max O₂ x 4.83Kcal/hr/m² • Efficiency = weight x 1069m/MaxMR

38. Percent Body Fat • Percent Body Fat Equation For Men • LBW = 98.42 + [1.082BW – 4.15WG] • %fat = BW – LBW x 100 / BW • LBW = lean body weight • BW = nude body weight in pounds (i.e 2.2 x Kg) • WG = waist circumference in inches at the level of the navel.

39. Percent Body Fat For Women • LBW = 8.987 + 0.732BW + 3.786WD – 0.157AC – 0.249HP + 0.434ArC • %fat = BW – LBW x 100 / BW • LBW = lean body weight in Kg • BW = nude body weight in Kg • WD = wrist diameter at the level of the styloid process in cm • AC = maximum abdominal circumference in cm • HP = hip maximum circumference in cm • ArC = forearm maximum circumference jus below the elbow in cm

40. Metabolic heat change, M = Vo₂ x 4.8 x 0.87. • Radiative heat exchange, R = 6.6 x (tw - tsk). • Evaporative heat loss, E = 14 x Va x 0.6 (Psk - Pa). • Convective heat exchange, C = 7 x Va x 0.6 (ta - tsk). • Respiratory heat loss, Res = 0.0014M (ta - tea) + 0.00173M (avp -vpea). • Change in heat content, ΔH = M+E+C+R+Res

41. Where tw = mean radiant temperature of the solid surrounding surface • Tsk = mean weighted skin temperature • Va = air speed in m/s • Pa = water pressure of ambient air in mmHg • Psk = vapour pressure of water on skin = 42 mmHg at 35 ̊C • Ta = air temperature in 25 ̊C • Tea = temperature of exhaled air = 35 ̊C • Avp = air vapour pressure = 23.76 mm Hg • Vpea vapour pressure of exhaled air = 42.1 mmHg.