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NUTRITION -1

NUTRITION -1. Contents. Introduction Nutritional significance of macronutrients BMR SDA Calorific value of food RQ RDA. Introduction. The science of nutrition examines the qualitative and quantitative requirements of the diet necessary to maintain good health.

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NUTRITION -1

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  1. NUTRITION -1

  2. Contents • Introduction • Nutritional significance of macronutrients • BMR • SDA • Calorific value of food • RQ • RDA

  3. Introduction • The science of nutrition examines the qualitative and quantitative requirements of the diet necessary to maintain good health. • NUTRIENTS are the constituents of food necessary to sustain the normal functions of the body.

  4. IMPORTANCE OF MACRONUTRIENTS • Energy yielding nutrients are provided by dietary carbohydrate , fat and to a lesser extent, protein in widely varying proportions among different human and animal populations. • Carbohydrate , fat and protein are referred to as PROXIMATE PRINCIPLE.

  5. Basal metabolic rate (BMR) • Definition • The basal metabolic rate (BMR) is the energy required by a person during complete physical, mental, emotional and digestive rest in a thermo neutral environment.

  6. Explanation of BMR • It is the minimum amount of energy required to maintain life • or • sustain vital functions like the working of the heart, circulation, brain function, respiration, metabolic activity etc…

  7. Measurement of BMR • Basal metabolic rate can be measured by; • CALORIMETER directly by measuring the heat dissipated under basal condition or • INDIRECTLY by measuring the oxygen consumed and CO2 evolved per unit time. Benedict – Roth basal metabolism apparatus is used.

  8. Normal value for BMR • The BMR is calculated from oxygen consumption, calorific value and surface area. It is usually expressed in kilocalories per hour per square meter of body surface. • For • Adult men 34-37 and adult women 30-35 Kcal/sq mt /hour. • For easier calculations, BMR of an adult is fixed as 24 Kcal/kg body wt/day.

  9. FACTORS AFFECTING BMR • 1) Age : • During the period of active growth BMR is high. It reaches a maximum by 5 years of age. In old age BMR is lowered. • 2) Sex: • Males have higher BMR than females. • 3) Temperature: • Increased in cold climate as a compensatory mechanism to maintain body temperature. Eskimos have a higher BMR.

  10. FACTORS AFFECTING BMR(cont’d) • 4) Exercise : • The increase in BMR during exercise is due to increased cardiac output. Starvation lowers BMR. • 5) Fever: • A 12% increase in BMR is noticed per degree centigrade rise in temperature. • 6)Thyroid hormones: • thyroid hormones have a general stimulant effect on rate of metabolism and heat production.

  11. Calorific value of food • The calorific value of food (energy content or energy density) is calculated from the heat released by the total combustion of 1G of food in a calorimeter. • Calorie is the unit of heat, and the energy content of food materials is thus measured in calories.

  12. Calorific value of the nutrients • Carbohydrates 4 Kcal/gm • Fats 9 Kcal/gm • Proteins 4 Kcal/gm

  13. Respiratory quotient (RQ) • The respiratory quotient (RQ) is the ratio of the volume of CO2 produced to the volume of O2utilised in the oxidation of food stuffs. • RQ of carbohydrates is 1; RQ of fats is 0.7; and that of proteins is 0.8 . • For a mixed diet it is between 0.7- 1, often around 0.82 -0.85.

  14. Specific dynamic action (SDA) • Definition: • It is the increased heat production by the body or increased metabolic rate following the intake of food. It is also termed as thermogenic effect of food. • This is the energy expended in the digestion, absorption and active transport of the products of the digestion. • Energy is also expended in storage and subsequent processing of food.

  15. SDA (cont’d) • SDA can be considered as the activation energy needed for a chemical reaction which is to be supplied initially. • The energy lost during during protein metabolism is the highest compared to fat or carbohydrates. • The values for SDA are: for proteins 30% , lipids 15% , and carbohydrates 5% .

  16. Nutritional importance (significance) of carbohydrate • Dietary carbohydrate is of two types. • Available or DIGESTIBLE carbohydrate And • Unavailable or INDIGESTIBLE carbohydrate

  17. Digestible carbohydrates • Major source of food energy, yielding 4Kcal/gm. Dietary carbohydrates provide about 60-65% of total calories. • Protein sparing effect. • Examples; • starch, sugars.

  18. Dietary fiber • The unavailable or indigestible carbohydrate in the diet is called dietary fiber. • Dietary fiber is necessary to maintain the normal motility of the GIT. • They are - • CELLULOSE,HEMICELLULOSE,LIGNIN,PECTINS,GUMS and MUCILAGES

  19. Sources: • plant foods like vegetables ,fruits and grains. • Requirement: 30gm/day.

  20. Importance( properties of dietary fiber) • A diet rich in fiber • Improves bowel motility and thus prevents constipation. It also holds water and swells like sponge thereby adding bulk to the stool. • Improves glucose tolerance (HYPOGLYCEMIC EFFECT) due to delaying of starch hydrolysis and glucose absorption. • It decreases reabsorption of bile acids thus lowering cholesterol levels in the blood

  21. Clinical application • High fiber diet is associated with reduced incidence of a number of diseases like; • coronary artery disease (CAD) • colon cancer • diabetes mellitus • diverticulosis and • haemorrhoids (piles).

  22. Significance (nutritional importance of lipids) • Dietary fats are high energy yielding nutrients that provide 30-45% of the total energy needs. • Fat yields 9Kcal/gm , thus a concentrated source of energy.

  23. Significance (nutritional importance of lipids) • Besides satisfying metabolic energy needs there are 2 essential functions of dietary fat: • 1)A vehicle for the absorption of the fat soluble vitamins(A,D,E & K) • 2) Supplies EFA. • They also increase the taste and palatability of food.

  24. Clinical application • The atherogenic effect of cholesterol and the risk of coronary artery disease is well established. • Hence it is always advisable that dietary intake of fat be restricted within the RDA limits.

  25. Significance(nutritional importance of proteins) • Proteins form the building blocks for body tissues. • Only 10-15% of the total energy is derived from proteins. • Dietary proteins are the only source of essential amino acids. • Proteins yield 4Kcal/gm.

  26. Energy requirements of a normal person • The energy expended by an individual depends on four main factors. • 1) Maintenance of basal metabolic rate(BMR) • 2) The thermogenic effect (SDA-Specific dynamic action ) of food. • 3) Physical activities

  27. Energy requirement for Indians • Caloric requirements of adults per day are in the following ranges; Body wtKcal/day • MAN Sedentary work 602425 • Moderate work 602875 • Heavy work 60 3800

  28. Body wt Kcal/day • WOMAN Sedentary work 501875 • Moderate work 502225 Heavy work 50 2925

  29. RDA ( recommended daily/dietary allowance) • RDA represents the quantity of nutrient sufficient for the maintenance of health in nearly all individuals. • The estimates of allowances are based on the defined minimum requirement plus a safety margin.

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