Summary: Recommended Dietary Allowances (RDA's) are levels of essential nutrients considered to be adequate to meet the known nutritional needs of most persons. They are established and updated by the National Academy of Sciences' (NAS) Food and Nutrition Board. RDA's have been criticized for the following: they are based on limited data; they overstate the needs of most individuals; they are limited to the needs of healthy people; and they do not cover all the essential nutrients. Most of these criticisms reflect limited scientific knowledge or misunderstandings of the purpose of RDA's. The high levels are established to cover variations in human needs and to cover the needs of most healthy individuals. RDA's are used in planning diets for groups, nutritional surveys, nutritional education, establishing guidelines for labeling, and in research-related activities. Comparisons with nutritional guidelines established in other countries revealed differences in dietary recommendations resulting from variations in people and lifestyles and differences of scientific opinion. RDA's are established through a reasonable process and serve their intended purpose. Additional research is needed to expand knowledge concerning nutrient requirements. NAS should identify these needs and establish priorities relating to human nutritional requirements. Also, more meaningful food planning and food choice guides for the consumer should be developed.
