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Specific dynamic action and nutrition
- 1. Specific Dynamic Action and Nutrition Dr. Rohini C Sane
- 2. Specific Dynamic Action(SDA) of food • Definition:The phenomenon of the extra heat production by the body over and above the calculated Caloric value, when a given food which is metabolised by the body is known as specific dynamic action(SDA). or SDA is increased metabolic rate following the intake of food . • SDA = Calorigenic action = thermic(effect)action /thermogenic action of food = diet induced thermogenesis • Part of this due to the expenditure of energy for digestion, absorption and active transport of products of digestion of food responsible for regulatory thermogenesis.
- 3. Specific Dynamic Action(SDA) of food Intake of Nutrient (25g) Calorie value (kcal) Heat liberation in human body (kcal) SDA(%) Carbohydrate 100(=25X4) 105 5 Protein 100(=25X4) 130 30 Lipid 100 115 15 Mixed diet ( regularly consumed) 10 Increased/ extra heat output after taking food is known as SDA. It is due to the activity of tissues mobilising these foodstuffs. Proteins have the highest SDA and carbohydrates have the lowest SDA. The energy is trapped from previously available energy, so that the actual energy from the food is lesser than that of calculated of SDA.
- 4. Thermogenic effect of food • Heat production (thermogenic effect of food) e.g. intake of carbohydrate :250 g • energy should produce = 250x 4 (kcal/g)=1000 kcal • energy trapped ( =10%) =100 kcal • Net energy generated =1000-100 = 900 kcal • If need is 1000 kcal then intake of food worth of 1100 kcal.
- 5. Specific Dynamic Action for proteins Highest SDA for proteins(30%) i.e. for 100 g of dietary proteins consumed , the energy available for doing useful work is 30% less than calculated value. Therefore it is not good source of energy. Diet very rich in protein unfavourable to heavy muscular activity. Expected heat generation on intake of 25 g of protein after overnight = 100 kcal(25 g x4) Actually heat output =130 kcal( rise of 30%) The presence of fats and carbohydrates reduces the SDA of proteins. SDA for proteins: to meet energy need / requirements for deamination , synthesis of urea , biosynthesis of proteins, biosynthesis of Triacylglycerol (from carbon skeletons of amino acids) , no absorption of proteins as such . Phenylalanine , Glycine and Alanine are fed increase SDA. Intravenous administration of amino acids or oral administration of proteins gives the same SDA. This indicates SDA of proteins ,is not due to their digestion and absorption. Benefits of SDA of protein : Consumption of protein rich diet makes us feel warm and comfortable in cold weather.This is due to the high SDA which help in maintenance of body temperature particularly in cold climate.
- 6. Specific dynamic action of lipids • SDA of lipid/fat =15% Heat output after ingestion of 11g of fat =113 kcal (11x9.1+13) not 100 kcal SDA for lipids : may be due to mobilisation ,storage and more rapid oxidation of fat. Fats is the best source of energy due to its lowering effect on SDA. However ,excessive utilisation of lipids leads to ketosis.
- 7. Specific dynamic action of carbohydrates • SDA of carbohydrates = 5% Heat output after ingestion of 25g carbohydrate =105 kcal (25x4)not 100 kcal. • SDA for carbohydrates : is attributed to the energy expenditure for conversion of Glucose to Glycogen.
- 8. Specific Dynamic action of a mixed diet SDA for mixed diet =10%(an extra energy/ calories should be provided in diet to account for loss of energy as SDA. e.g.calorie requirement to maintain basal metabolic needs: 1700 kcal/day Heat output after eating food = 1700+170 kcal(excess calorie derived from his own tissue) Energy requirement to maintain his weight =1900 kcal(1700+170) If persisted intaking 1700 kcal ,it would result in loss of the body weight .
- 9. Mechanism of Specific Dynamic Action • Excess energy (SDA) is required for digestion,absorption ,transport, metabolism and storage of foods in the human body. • SDA for carbohydrates(5%): is attributed to the energy expenditure for conversion of Glucose to Glycogen. • Higher SDA of proteins (30%) is due to meet extra energy requirement for energy utilisation for deamination , synthesis of urea , biosynthesis of proteins, biosynthesis of Triacylglycerol (from carbon skeletons of amino acids) , no absorption of proteins as such . Therefore ,it is not good source of energy. Phenylalanine , Glycine and Alanine decrease SDA. Intravenous administration of amino acids or oral administration of proteins gives the same SDA. This indicates SDA of proteins ,is not due to their digestion and absorption. • SDA for lipids(15%) : may be due to mobilisation ,storage and oxidation of fat.
- 10. Significance of specific Dynamic action:1 • Additional 10% calories should be added to the total energy needs of the body towards SDA for: 1. the extra heat liberated over and above the calorie value. It may be due to a specific stimulating effect of food on metabolism. 2. digestion,absorption ,transport, metabolism of foods in the human body. 3. consumption of certain amount of energy for utilisation of nutrients from the body stores(e.g. glycogen, triacyl glycerol, protein) by the human body. 4. synthesis of reserve materials such as glycogen , triacylglycerol , protein etc. from small molecules available after digestion in the human body . 5. the activation energy needed for a chemical reaction and this activation energy to be supplied initially. It is closely connected with the metabolic functions of liver.
- 11. Significance of specific Dynamic action:2 6. Higher SDA of proteins (30%) is due to extra energy utilisation for deamination , synthesis of urea , biosynthesis of proteins, biosynthesis of Triacylglycerol (from carbon skeletons of amino acids) , no absorption of proteins as such . Therefore ,it is not good source of energy. 7. for conversion of Glucose to Glycogen and fatty acids to Triacylglycerol for storage of energy. 8. Fats is the best source of energy due to its lowering effect on SDA. However ,excessive utilisation of lipids leads to ketosis.
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