These numerical values provide nutrition guidance to health professionals and to the general public. You may have heard, for example, that the RDA for vitamin C is 60 milligrams per day for adults. RDAs are defined as the levels of intake of essential nutrients that are judged to be adequate to meet the known needs of practically all healthy persons. In addition to providing information for labels on food, RDAs are used for many other purposes.
Institutions use the RDAs to plan healthful diets for schools, prisons, hospitals and nursing homes.
Industry uses them to develop new food products. Policy makers use them to evaluate and improve food supplies to meet national needs, and health workers use them to provide nutrition education. Since 1941, when the first RDAs were published, they have been updated 10 times. RDAs were set for different age groups, for men and women, and for pregnant and nursing mothers. In 1995, the Food and Nutrition Board deemed that a new, more comprehensive approach was necessary to setting dietary guidelines.