RECOMMENDED DIETARY ALLOWANCES
Since individual variations are high, the ICMR has suggested the recommended allowances based on reference Indian man and woman.
Reference Indian man has been defined as 'an adult man between 20 - 39 years of age, weighing 60 kg. He is free from diseases and physically fit for active work. On each working day he is employed for eight hours in occupation that usually involves moderate activity. While not at work he spends eight hours in bed, four to six hours in sitting and moving about and two hours in walking, active recreation or house hold duties'. For such a reference man the ICMR has taken an average height of 163 cm.
Reference Indian woman is defined as 'an adult woman between 20 - 39 years of age, weighing 50 kg. She may be engaged for eight hours in general house hold work, in light industry or in any other moderately active work. Apart from eight hours in bed, she spends four to six hours in sitting and moving around (light activity) and two hours in walking, active recreation or household duties'. For such as reference woman the ICMR has taken a height of 151 cm.
The RDA for an adult man and woman engaged in different activities is tabulated in Table 7.1.
The energy requirement of an individual has been defined as 'the level of energy intake from food that will balance energy expenditure when the individual has body size and composition and level of physical activity, consistent with long term good health and that will allow for maintenance of economically necessary and socially desirable activity'.
1. The components of energy expenditure include
2. Basal Metabolic Rate (BMR)
3. Regulatory thermogenesis which includes the metabolic response to food ingested and stimuli such as cold, stimulants and drugs.
4. Nature and duration of activity. The allowances for those engaged in heavy work should be higher than those doing either sedentary or moderate work.
Studies on Indian adults have revealed that the minimum intake of dietary protein to maintain nitrogen equilibrium, on an average, is 0.58 g/kg body weight. After allowing for sweat losses the intake works out to 0.7 g/kg. The corresponding safe level of intake has been computed to be 0.88 g/kg body weight. Hence the ICMR has recommended 1.0 g protein per kg body weight for both men and women. Since protein needs are not affected by activity the RDA for an protein is 60 g/day and 50 g/day for adult man and adult woman respectively.
The two factors that need to be considered while assessing fat requirements are
1. The invisible fat in the diet which supplies majority of the essential fatty acid requirements.
2. A certain amount of visible fat is required to meet requirements of two essential fatty acids i.e., linoliec and linolenic fatty acids.
The requirement of linoleic acid has been estimated to be 3 percent of total energy requirement, which can be met by 12 g of visible fat. To provide energy density and palatability to the diet the ICMR has suggested 20 g visible fat per day. The type of visible fat used is also important. Oils containing high amount of saturated fatty acids may increase the linoleic acid requirements and are detrimental to health. Hence combination of oils with equal proportion of saturated, monounsaturated and polyunsaturated fatty acids has been recommended.
4. Calcium and phosphorus
In adults calcium is required for replacing calcium lost from body through urine, faeces, sweat and bile. Of the dietary calcium only 20 to 30 percent is absorbed and this is facilitated by vitamin D. Long term balance studies have shown that a positive calcium balance can be achieved by an intake of 300 to 500 mg of calcium daily. ICMR has suggested 400 mg calcium / day for both men and women.
Along with this, a desirable intake of phosphorus is recommended as the functions of calcium and phosphorus is closely linked. The elemental Ca:P ratio in the diet should be maintained at 1:1.
The loss of iron through sweat, gastrointestinal tract and urine is estimated to be 14 mg/kg body weight. Apart from this women have additional loss due to menstruation which varies between 0.5 to 1mg per day (an addition of 16 mg/kg taken as the upper limit). Based on these the iron requirements are arrived at as 28 mg for men and 30 mg for women per day respectively.
a. Vitamin A
Studies have revealed that 600 mg of retinol daily would be sufficient to maintain a normal serum vitamin A level at 20 mg / 100 ml. Hence the ICMR has suggested 600 mg of retinol for both men and women equivalent to 2400 mg of b carotene. Since Indian diets contain both retinol and b carotene it is advisable to express the Vitamin A content of diet in terms of retinol equivalents.
Retinol equivalent = mg of retinol + ¼mg of b - carotene.
b. B Complex vitamins
The requirement for B Vitamins is based on calorie intake i.e. 0.5 mg / 1000 k.cal, 0.6mg / 1000 k.cal and 6.6 mg / 1000 k.cal for thiamine, riboflavin and niacin respectively. The RDA for pyridoxine is 2.0 mg/day for both adult man and woman.
The minimal daily requirement of folic acid among Indians is 75 mg of folate. In this view the safe level of intake has been suggested to be 100 mg of folate per day. Due to lack of precise data on bioavailability of food folates ICMR has recommended 100 mg of free folate per day for adults.
c. Vitamin C (Ascorbic acid)
The concentration of Vitamin C in circulating leukocytes reflects the tissue concentration. Based on this a daily intake of 20 mg vitamin C is sufficient to maintain satisfactory ascorbic acid status. Considering 50 percent loss of vitamin C during cooking ICMR has recommended RDA of 40 mg vitamin C per day for both men and women.