UNIT 3: FOOD NUTRIENTS COMMUNITY HEALTH NUTRITION BSPH 314 CHITUNDU KASASE BACHELOR OF SCIENCE IN PUBLIC HEALTH UNIVERSITY OF LUSAKA 1. Nutrients 2. Energy requirements 3. Dietary requirements. 4. Dietary Guidelines 5. RDA s The Two Classes of Nutrients ENERGY REQUIREMENTS 1. Energy Yielding: Carbohydrate, Fat, Protein 2. Non-energy Yielding: Vitamins, Minerals, Water 1
ACQUIRING NUTRIENTS Overview nutrients digestion, absorption glucose, amino acids, fats distribution precursors, available fuels metabolism macromolecules, energy, end products WHY IS INTAKE IMPORTANT? 1. Meet nutritional needs. 2. Avoid nutrient deficiencies. 3. Prevent nutrient toxicity. ENERGY RECOMMENDATIONS Estimated Energy Requirement Acceptable Macronutrient Distribution Ranges Carbohydrate: 45% - 65% Fat: 20% - 35% Protein: 10% - 35% The body uses most of its energy intake for basal metabolic work needs. Food energy is changed into body energy and cycled throughout the body to do work. 2
BASIC ENERGY NEEDS The body needs constant energy for voluntary and involuntary activity Voluntary work and exercise Includes all physical actions related to usual activities and additional physical exercise Basic Energy Needs Involuntary work: includes all activities of the body that are not consciously performed Circulation, respiration, digestion, other internal activities Requirements include: Chemical energy: in many metabolic products Electrical energy: in brain and nerve activities Mechanical energy: in muscle contraction Thermal energy: to keep the body warm Basic Energy Needs Fuel is provided in the form of nutrients Three energy nutrients: Carbohydrate is primary fuel Fat assists as storage fuel Protein is a back-up fuel source If sufficient carbohydrate is not consumed to meet energy needs, the body burns fat MEASUREMENT OF ENERGY Calorie: Amount of energy in food or expended in physical actions (common usage) Kilocalorie (1000 calories) Amount of heat necessary to raise 1 kg of water 1 degree Centigrade Large calorie unit used in nutritional science to avoid dealing with large numbers Abbreviation: kcalorie or kcal (1 kcal = 4.184 kj) 3
Carbohydrate: Fat: Protein: Alcohol: FUEL FACTORS 4 kcal/g 9 kcal/g 4 kcal/g 7 kcal/g ENERGY INTAKE The body s energy balance depends on energy intake in relation to energy output. Energy intake Three energy nutrients in food Energy intake is the calculated energy value of actual food consumption ENERGY OUTPUT Activities to sustain life require energy from food and body reserves Three demands for energy determine the body s total energy requirements 1. Resting energy expenditure (REE) 2. Physical activity 3. Thermic effect of food RESTING ENERGY EXPENDITURE (REE) Sum of all internal working activities of the body at rest Expressed as kcal/day Basal energy expenditure (BEE) is similar to REE, but requires complete physical rest (difficult to achieve) 4
Measurement of Basal Metabolic Rate General formula Men 1 kcal x kg body weight x 24 hours Women 0.9 kcal x kg body weight x 24 hours Factors affecting the metabolic rate: 1-Muscular exercise (most imp. Factor) Maximal exercise can increase the metabolic rate to 200 % of normal, there is increased O2 consumption 2-Recent food ingestion Specific dynamic action of food-sda - It is defined as the obligatory energy expenditure that occurs during food assimilation into the body. It is affected by : a- Type of food :an amount of proteins( provide 100 kcal) can increase total metabolism by 30 kcal, a similar amount of carbohydrates increases it 6 kcal& a similar amount of fat increases it by 4 calories. b- Amount of food 3- Environmental temperature: When it is lower than body temperature, the metabolic rate increases due activation of heat conserving mechanisms. Persons living in cold climate have increased thyroxin. 4-Fevers increase the metabolic rate because it increase the cellular chemical reactions. 1 C increases metabolic rate 14% of basal level. 5-Sympathetic stimulation increases metabolic rate due to liberation of catecholamines which causes muscle& liver glycogenolysis. 6-Sleep Metabolic rate falls to 15% below normal due to decreased Skeletal muscle tone& decreased sympathetic activity. 7-Age: It is greater in young children due to high rate of cellular reactions needed for growth. 8- Sex Metabolic rate is higher in males than Females due to stimulatory effect of testosterone & great muscle bulk. 5
9-Hormones Sex hormones, thyroxine & growth hormones, all stimulate cellular metabolism. 10-Malnutrition decreases metabolic rate due to decrease in circulating catecholamines & thyroid hormone specially with prolonged starvation with decresed necessary food substances in the cells. 11- Emotional state Anxiety& tension elevate the metabolic rate due to increased epinephrine, but depression decreases metabolic rate. 12-Race Pure races as Chinese and Indians have a lower BMR than mixed races as Americans & Egyptians. PHYSICAL ACTIVITY Energy expenditure for physical activity goes above and beyond energy used for resting energy needs Energy output during physical activity varies widely across individuals Physical activity level (PAL) Global activity during a fixed time period PAL value for one year Very light, Male = 1.30 and female = 1.30 light, Male = 1.55 and female = 1.56 Moderate, Male = 1.78 and female = 1.64 heavy activity Male = 2.10 and female = 1.82 exceptional Male = 2.40 and female = 2.20 THERMIC EFFECT OF FOOD After eating, food stimulates metabolism and Extra energy for digestion, absorption, and transport is required. This stimulating effect is called the Thermic Effect of Food (TEF). 5%-10% of the body s total energy needs for metabolism relates to the processing of food 6
TOTAL ENERGY REQUIREMENT Total energy requirement = +Resting energy expenditure (BMR) + Physical activity + Thermic effect of food Total Energy Expenditure 7