Lecture 35: Principles of Nutrition (1) PDF

Lippincott’s illustrated reviews Chapter 27 – Page 355 Lecture 35 Principles of Nutrition (1) 1  Specific Objectives By the end of this lecture students can be able to: Understand dietary reference intakes. Explain how energy is used in the body. 2...

Lippincott’s illustrated reviews Chapter 27 – Page 355 Lecture 35 Principles of Nutrition (1) 1  Specific Objectives By the end of this lecture students can be able to: Understand dietary reference intakes. Explain how energy is used in the body. 2 3 Nutrients are the constituents of food necessary to sustain the normal functions of the body. Macronutrients are nutrient needed in large amounts as fats, carbohydrates and protein These are needed to maintain optimal health and prevent chronic disease in adults. Micronutrients needed in lesser amounts are vitamins and minerals. 4  Dietary reference intakes (DRI) Estimates of the amounts of nutrients required to prevent deficiencies and maintain optimal health and growth. The DRIs replace and expand on the: 5 1. Estimated Average Requirement (EAR) 6 2. Recommended Dietary Allowance (RDA): The RDA is the average daily dietary intake level that is sufficient to meet the nutrient requirements of nearly all (97–98%) the individuals in a life stage and gender group. 7 3. Adequate Intake (AI): The AI is based on estimates of nutrient intake by a group (or groups) of apparently healthy people that are assumed to be adequate. 4.Tolerable Upper Intake Level (UL): The UL is the highest average daily nutrient intake level that is likely to pose no risk of adverse health effects to almost all individuals in the general population. As intake increases above the UL, the potential risk of adverse effects may increase. Intakes between the UL and the RDA can be considered to have no risk for adverse effects. 8  Energy requirement in humans The Estimated Energy Requirement is the average dietary energy intake predicted to maintain an energy balance (that is, when the calories consumed are equal to the energy expended) in a healthy adult of a defined age, gender, and height whose weight and level of physical activity 9 A. Energy content of food The energy content of food is calculated from the heat released by the total combustion of food in a calorimeter. It is expressed in kilocalories (kcal, or Cal). [Note: The joule is a unit of energy widely used in countries other than the United States. For uniformity, many scientists, One Cal = 4.2 J; 1Cal 10 (1 kcal, 1 food calorie) = 4.2 J. B. How energy is used in the body The energy generated by metabolism of the macronutrients is used for three energy-requiring processes that occur in the body: 11 1.Resting metabolic rate: (RMR) The energy expended by an individual in a resting, post absorptive state is called the resting (formerly, basal) metabolic rate (RMR). It represents the energy required to carry out the normal body functions, such as respiration, blood flow, ion transport, and maintenance of cellular integrity. From 50–70% of the daily energy expenditure in sedentary individuals is attributable to the RMR. 12 2. Thermic effect of food: The production of heat by the body increases as much as 30% above the resting level during the digestion and absorption of food. This effect is called the thermic effect of food or diet- induced thermogenesis. sociirringomophonooooookhook ohmaoohhhhhhafessishoissassissss Over a 24–hour period, the thermic response to food intake may amount to 5–10% of the total energy expenditure. 13 3. Physical activity: Muscular activity provides the greatest variation in energy expenditure. In general, a sedentary person requires about 30– 50% more than the resting caloric requirement for energy balance, whereas a highly active individual may require 100% or more calories above the RMR. 14 15 Reference Book: Champe, P. C., Harvey, R. A. and Ferrier, D. R., 2005. Biochemistry “Lippincott’s Illustrated Reviews”, 5th or 6th Edition 16