Physiological Value of Food

CHAPTER 6 PHYSIOLOGIC VALUE OF FOOD Objectives At the end of the chapter, the students should be able to: 1. calculate the physiologic value of food; and 2. compute the desirable body weight and energy needs of an adult. FOOD Food refers to the solid and liquid materials taken into the digestive tra...

CHAPTER 6 PHYSIOLOGIC VALUE OF FOOD Objectives At the end of the chapter, the students should be able to: 1. calculate the physiologic value of food; and 2. compute the desirable body weight and energy needs of an adult. FOOD Food refers to the solid and liquid materials taken into the digestive tract that are utilized to maintain and build body tissues, regulate body processes, and supply heat, thereby sustaining life. Food is composed of various compounds, both organic and inorganic, so that any food is either a chemical compound or a mixture of chemical compounds. These compounds and elements can be grouped as either organic and inorganic. Organic compounds are proteins, lipids, carbohydrates, and vitamins. Inorganic elements are water and minerals. The three major nutrients-carbohydrates, proteins, and fats-stand quite apart from the other requirements of the body such as vitamins and minerals since the former are needed in comparatively larger quantities. Vitamins and minerals act as catalysts which prompt the three major nutrients to interact. METABOLISM The word metabolism is derived from the Greek word metabolismos which means to change or alter. Metabolism is the chemical process of transforming food into complex tissue elements and of transforming complex body substances into simple ones, along with the production of heat and energy. It is the totality of the chemical processes in the body by which substances are changed into other substances to sustain life, thus it is the dynamic concept of change underlying all life. Energy is the force or power that enables the body to do its work. In nutrition, however, energy pertains to the chemical energy locked in foodstuffs brought about by metabolism. ENERGY FROM FOOD The Calorie The unit of energy commonly used in human nutrition is the kilogram calorie (kcal) or simply calorie. It is the unit of measurement for the energy that the body gets from food. 1,000 small calories = 1 kilocalorie or calorie Calories are not eaten. They are by-products of carbohydrates, proteins, and fats that are oxidized in the body. One kilocalorie is the amount of heat energy required to raise the temperature of 1 kilogram of water by 1°C. 1. Fuel factor of carbohydrate = 4 calories per gram 2. Fuel factor of fat - 9 calories per gram 3. Fuel factor of protein = 4 calories per gram The total calorie content (total energy) available from food can. be measured by a device called a bomb calorimeter. The Joule The joule is the measure of energy in the metric system. 1 calorie (kilocalorie) = 4.184 joule (kilojoules) Example: 1 cup of milk = 170 kcal 170 kcal x 4.184 kjoules = 711.28 kjoules Calculation of Food Value The energy value of one tablespoon of sugar (15 grams) is approximately 60 calories (15 × 4). Most foods, however, are complex and contain proteins, fats, and carbohydrates. For example, one cup of milk contains approximately: 12 gms carbohydrates × 4 cal/gm = 48 kcal 8 gms proteins x 4 cal/ gm = 32 kcal 10 gms fats × 9 cal/gm = 90 kcal Total = 170 kcal From this information, the percentage of each nutrient can be calculated. To calculate the percentage of kcalories from fat, for example, divide the 90 fat kcal by the total 170 kcal. 90 fat kcal / 170 kcal = 0.529 or 0.53 0.53 = 53% Table 31 Energy Allowances for Adults 22 Years of Age Body Weight (kg) Women (kcal) Women Men (kcal) Men (kJoules) (kJoules) 40 1,550 6,500 - - 45 1,700 7,100 - - 50 1,800 7,500 2,200 9,200 55 1,950 8,200 2,350 9,800 60 2,000 8,400 2,500 10,500 65 2,050 8,600 2,650 11,100 70 2,200 9,200 2,800 11,700 75 2,300 9,600 2,950 12,300  80 - - 3,050 12,800 85 - - 3,200 13,400 90 - - 3,350 14,000 COMPONENTS OF ENERGY EXPENDITURE Basal Metabolism Basal metabolism, also known as the required energy expenditure (REE), is the measure of energy needed by the body at rest for all its internal chemical activities which is approximately 1 calorie per kilogram of body weight per hour for an adult. It is the minimum amount of energy needed by the body at rest in the fasting state. It also indicates the amount of energy needed to suction the life processes: respiration, cellular metabolism, circulation, glandular activity, and the maintenance of body temperature. It accounts for more than one-half of calorie requirements for most people. The basal metabolic rate (BMR) is the rate of basal metabolism in a given person at a given time and situation. It constitutes one-half of the calorie requirements of an individual Conditions Necessary for BMR Test To ensure accuracy: 1. The subject must be in fasting or post-absorptive state, at least 1 hour after the meal. (The test is usually taken in the morning.) 2. The subject must be awake, lying quietly, and free from physical fatigue, nervousness, or tension as this causes an increase in heat production. 3. The environmental temperature should be between 20 °C - 25 °C so that the subject can maintain his/her body temperature. Values obtained in this test which are within the plus or minus 10% are still considered normal. Calculation of BMR 1. A simple method for the calculation of the BMR is to use the rule of thumb 1 kcal per kg per hour for adult male and 0.9 kcal per kg per hour for adult female. Thus, an individual whose ideal body weight (IBW) is 50 kg has a basal metabolic energy need of 1,200 kcal per day (50 x 1 kcal x 24 hrs). This value, however, may not be applicable for obese or lean individuals. Example: Male, 75 kg = 1 kcal × 75 × 24 = 1,800 kcal Female, 65 kg = 0.9 kcal × 65 × 24 = 1,404 kcal 2. Another method is the Harris-Benedict formula, developed in 1909, which uses information on weight, height, age, and sex. Example: Males REE = 66 + [13.7 x wt(kg)] + [5 x ht(cm)] - [6.8 x age (yr)] Females REE = 655 + [9.6 x wt(kg)] + [18 x ht(cm)] - [4.7 x age (r)] 3. One more method used in obtaining the metabolic or fat-free body size is called the biologic body weight raised to the ¾ power. The metabolic body size for the different body weights is given in Table 32. Once the metabolic body size is known based on weight in kilograms, the figure is multiplied by 70, a value which applies to all animals. A 50-kg man's REE = 18.8 × 70 = 1,326 kcal 4. The last method is developed by WHO/FAO/UNU in 1985. It uses the following equation: 1.6 x wt (kg) + 879 = REE Thus, a 50-kg man has a REE of 1,459 kcal. Table 32 Body Weights in Kilogram and Metabolic Body Size (kg)¾ Body Weights Metabolic Body Size (kg) (kg)¾ 5 3.3 10 5.6 15 7.6 20 9.5 25 12.1 30 12.8 35 14.4 40 15.9  45 17.4 50 18.8 65 21.6 70 24.2 80 26.7 90 29.2 100 31.6 Factors that Affect the Basal Metabolic Rate (BMR) 1. Surface area - The greater the body surface area or skin area, the greater the amount of heat loss, and, in turn, the greater the necessary heat produced by the body, Muscle issue requires more oxygen than adipose tissue. 2. Sex - Women, in general, have a metabolism of about 5% to 10% less than that of men even when they are of the same weight and height. Women have a little more fat and less muscular development than men. 3. Age - The metabolic rate is highest during the periods of rapid growth, chiefly during the first and second years, and reaches a lesser peak through the ages of puberty and adolescence in both sexes. The BMR declines slowly with increasing age to lower muscle tone from lessened activity. 4. Body composition - A large proportion of inactive adipose tissue lowers the BMR. Athletes with great muscular development show about 5% increase in basal metabolism over non-athletic individuals. 5. State of nutrition - A decrease in the mass of active tissue such as in the case of undernourishment or starvation causes a lowered metabolism often as much as 50% below normal. 6. Sleep - During sleep, the metabolic rate falls approximately 10% to 15% below that of waking levels. This decreased rate is due to muscular relaxation and decreased activity of the sympathetic nervous system. 7. Endocrine glands - The endocrine glands, which secrete hormones into the blood stream, are the principal regulators of the metabolic rate. The male sex hormones increase the BMR about 10% to 15% and the female sex hormones a little less. 8. Fever - It increases the BMR about 7% for each degree rise in the body temperature above 98.6 °F. Computation of DBW (Desirable Body Weight) 1. Ador Dionisio's Method Height - For every 5 feet, allow 100 lbs for female and 110 lbs for male. Then multiply the additional inches by 2. Age - Multiply any age between 25 and 50 by 2 then divide by 5. Example: Male, 45 years old, 5'4" tall Height = 5 feet = 110 lbs 4 inches x 2 = 8 lbs 118 lbs Age = (45 years)2 = 18 lbs 5 DBW = 118 lbs + 18 lbs = 136 lbs 2. Tannhauser's Method Measure height in cm and deduct 100. From the difference, take off its 10%. Example: Male, 45 years old, 5'4" tall Height = 5'4" = 162.56 cm 162.56 - 100 = 62.56 cm 10% of 62.56 cm = 6.256 62.56 - 6.256 = DBW (kg) DBW (kg) = 56.7 kg or 126 lbs Physical Activity Calorie requirements depend on the type and amount of exercise. The more vigorous the physical work, the greater the calorie cost. The kind of physical activity and the amount of time spent determine the amount of energy the body uses. Table 34: Calorie Expenditure for Various Types of Activities Calories Burned Sedentary Activities 80-100 - reading, writing, eating, watching TV, office work, sitting at work Light Activities 110-160 - cooking, washing dishes, ironing, welding, standing at work, rapid typing  Moderate Activities 170-240 - mopping, scrubbing, sweeping, gardening, carpentry, walking fast - standing at work with moderate arm movement - sitting at work with vigorous arm movement Heavy Activities 250-350 - heavy scrubbing, hand washing, walking fast, bowling, golfing, heavy gardening Specific Dynamic Action of Food Carbohydrate or fat increases the heat production of about 5% of the total calories consumed. It is the energy required to digest, transport, and utilize food. Estimation of Daily Energy Requirement of an Adult The daily energy requirement of an adult is commonly estimated by adding together the requirements for basal metabolism, physical or muscular activity, and the specific dynamic action (SDA) of food: 1. Determine the DBW in kg of the individual. 2. Determine the basal needs: Male - 1.0 kcalorie/kilo of DBW/hr × 24 Female = 0.9 kcalorie/kilo of DBW/hr × 24 3. Subtract 0.1 kcalorie/kilo of DBW/hours of sleep. 4. Add the activity increment. 5. Add the SDA (10% of basal needs + activity increment). 6. Sum equals the approximate daily calorie requirement. Table 35: Activity Increment Men Women Sedentary or light work 225 225 Moderate work 750 500 Heavy work 1,500 1,000 Very heavy work 2,500 - Estimation of Total Energy Need The total energy need of an individual is the composite of energy necessary to replace basal metabolic needs, energy expenditure for physical activities, thermogenic effect of food, and other factors. The total energy need of an adult may be determined using one of the methods on the following pages. 1. The most practical and rapid method of estimating energy need is based on desirable body weight (DBW) according to occupation. This method is often used in clinics and hospitals. Table 36: Occupation Female Female Male Male or Activity kcal/lb kcal/kg kcal/lb kcal/kg Bed patient 12 25 14 30 Light work 14 30 16 35 Moderate work 16 35 18 40 Heavy work 18 40 20 44 Example: 50 kg man x 40 (moderately active) = 2,000 kcal/ day 2. The second method of estimating the energy need is the factorial method. It uses the following equation: Basal energy (a) + physical activity (b) + thermogenic effect of food (c) = total energy need a. Calculate the basal metabolic rate using any of the four methods discussed earlier. b. Determine the energy need for physical activity (PA) by using the short method (Table 34). c. Add the basal energy cost and activity cost. a. Calculate the thermogenic effect of food. For a mixed diet adequate in protein, add 10% of the subtotal. For the average Filipino diet, use 6%. e. Add the basal energy, physical activity, and thermogenic effect of food. Example: a. Basal metabolic rate using the Harris & Benedict formula REE = 66.5 + [13 × 50 kg] + [5.0 × 157 cm] - [6.8 × 35 (age)] = 66.5 + 685 + 785 - 238 = 299 kcal = basal metabolic needs b. Energy need from PA = total PA kcal x 50 (wt in kg) = 17.24 kcal × 50 kg = 862 kcal for PA c. Basal energy cost and activity cost = 1,299 kcal + 862 kcal = 2,161 kcal d. Thermogenic effect of food = basal energy cost + activity cost × 6% = (1,299 kcal + 862 kcal) (0.06) = 2,161 × 0.06 = 130 e. Basal energy cost, activity cost, and thermogenic effect = 1,299 kcal + 862 kcal + 130 kcal = 2,291 kcal Table 37 Approximate Increase Above Basal Need for Selected Activities Activity Category Percentage Above Basal Sleeping, Reclining 10% Very Light Activities 30% (sitting and standing, painting, driving, laboratory work, typing, playing musical instruments, sewing, ironing) Light Activities 50% (walking on level 2.5-3 mph, tailoring, pressing, garbage work, electrical trades, carpentry work, washing clothes, golfing, sailing, playing table tennis, playing volleyball) Moderate Activities 75% (walking on 3.5-4 mph, plastering, weeding and hoeing, loading and stacking bales, scrubbing floors, shopping with heavy load, cycling, skiing, playing tennis, dancing) Heavy Activities 100% (walking with lead uphill, tree-felling, work with pick and shovel, playing basketball, swimming, climbing, playing football) 3. The daily energy need can also be determined by referring to the recommended dietary allowances for Filipinos (see Table 38), Table 38 Recommended Daily Energy Intake for Adults Age Men (Calories) Women (Calories) 20-31 2,580 1,920 40-49 2,450 1,820 50-59 2,320 1,730 60-69 2,060 1,540 70-79 1,810 1,340 4. The fourth method is recommended by FAO/WHO/UNU (1985). To get the energy need, multiply REE by the type of activity. Table 39: Energy Based on Type of Men Women Activity Very Light 1.3 1.3 Light 1.6 1.5 Moderate 1.7 1.6 Heavy 2.1 1.9 Very Heavy 2.4 2.2 Example: Basal metabolic needs of a 50-kg man is 1,459 kcal * 1.7 (moderate) = 2,480 kcal Energy Balance The amount of energy taken in by an individual should be equal to the amount of energy expended during the day. If this is so, then the individual is said to be in energy balance and, thus, attains a desirable body weight. A desirable or ideal body weight is still debatable since body weight is made up of fats, muscles, organs, bones, and fluid. Two individuals having the same height and age may not necessarily have the same weight because of the aforementioned components. In the absence of tables, any of the two methods shown here may be used. 1. Tannhauser's Method Height in centimeter = 157cm (factor) = 100 = 57 kg (10% of answer obtained to adjust weight to suit the Filipino standard) = 5.7 = 51.3 or 51 kg 2. For 5 feet, allow 100-105 Ibs (females); 105-110 Ibs (males). For each additional inch, add 5 lbs. 5'2" = 105 +10 = 115 lbs The values above apply to adults with small frame. Add 5 lbs for medium frame and 10 lbs for large frame.