The Recommended Daily Allowance (RDA) is defined as the average daily dietary nutrient intake level sufficient to meet the nutrient requirement of nearly all (97 to 98 percent) healthy individuals in a particular life stage and gender group. In simple words it means the level of nutrients that must be present in the daily diet to meet all the requirements of individuals in a given population. The daily dietary intake must be enough to meet the physiological needs of practically all healthy persons in a group with specified characteristics. The recommended dietary intake is based on available scientific knowledge.
In India, the first attempt to define nutrient requirements and desirable dietary intakes of nutrients for Indians to maintain good health was made in 1944 by the Nutrition Advisory Committee of the Indian Research Fund Association which is now the Indian Council of Medical Research (ICMR). At that time, the requirement and allowances of only energy, protein, iron, calcium, vitamin A, thiamine, riboflavin, ascorbic acid and vitamin D were considered. Based on these nutrients a typical balanced diet based on Indian dietary habits was formulated so that it would provide all the nutrients for a normal adult man of 55 kg and a normal adult woman of 45 kg body weight.
However, the Expert Groups of the ICMR along with the National Institute of Nutrition (NIN) has now revised and updated the nutrient requirement and RDA according to requirements of modern times. This revision is based on the knowledge generated by Indian research and on International Reports especially by those of the FAO, WHO and UNU. Accordingly newer nutrients and dietary components like selenium, B6 and dietary fibre and antioxidants are also taken into consideration now.
Humans require a wide range of nutrients to lead a healthy and active life. The nutrients for different physiological groups are different and are derived from a well- balanced diet. The diet needs to be composed judiciously so that it provides each individual with the right amount of nutrients according to his/her age, body weight and physiological status.
Adults require nutrients for the maintenance of constant body weight and for proper body functions. Infants and young children grow rapidly and require nutrients not only for maintenance but also for growth. They require relatively two to three times more nutrients per kg body weight than adults. In pregnancy and during lactation, adult woman need additional nutrients to meet the demand for the growth of the foetus and for milk secretion during lactation. These extra intakes of nutrients are essential for normal growth of infants in utero and during early post-natal life.
The RDA for the various groups of populations and individuals is different. For individuals the nutrients and dietary requirements are based on age, body weight and physiological and metabolic status of the individual. Considerations to keep in mind for population groups must take into account individual variation within the group, quality of the diet, effect of cooking and processing and bio-availability of the nutrient from the diet.