What Is United States Recommended Daily Allowances (USRDA)

USRDAs were devised by the Food and Drug Administration for nutritional labeling. These are the lists on processed foods and vitamin products that tell what percentage of each of 19 essential nutrients you get per serving or dose. It is a rough guide because it doesn't differentiate among people of different ages and sex who have different nutrient requirements.

The USRDAs, in turn, are based on the RDAs- Recommended Dietary Allowances derived by a prestigious group of nutritional scientists who advise the Food and Nutrition Board, a committee of the National Academy of Sciences-National Research Council. Every five years or so, the board reviews and revises its recommendations. As the board defines them, the RDAs are "the levels of intake of essential nutrients considered, in the judgment of the Food and Nutrition Board on the basis of available scientific knowledge, to be adequate to meet the known nutritional needs of practically all healthy persons."

Except for vitamins A and D, it's not harmful to consume two to three times the recommended levels of vitamins. Many people regularly do through the foods they eat and especially if they take a multivitamin supplement.

Shortcomings of the Recommended Daily Allowances

There are some caveats regarding the RDAs. The board that established them admits that scientific knowledge of nutritional requirements is far from complete: that the requirements for many nutrients have not been established; that several essential nutrients have only recently been discovered; and that in all likelihood other nutrients will be found to be essential in years to come. Therefore, to be sure that as yet undefined nutritional needs are met, it's important to eat a varied diet and not depend on pills or processed foods artificially stoked with known micronutrients.

The RDAs should not be confused with nutritional requirements. Requirements differ from individual to individual because of inherent genetic differences, among other factors. Therefore, the RDAs represent estimates that exceed the requirements of most people.

The RDAs were developed for healthy people under normal circumstances (i.e., no illness, no genetic weaknesses, no environmental toxin exposure) to prevent the development of overt deficiency diseases. They were not developed to serve as a guide to determining optimal nutritional needs.

In addition, the studies that were used to determine the level of a nutrient sufficient to prevent a nutritional deficiency were typically conducted for six to nine months, only about 1% of the average human life span. Nutritional studies with animals have shown that the amounts of some nutrients sufficient to provide health and the prevention of a deficiency disease for short periods of time may be totally inadequate to maintain the health of the animal over its entire lifespan.

Next Topic: 

Table of United States Recommended Daily Allowances (USRDA)

Recommeded Daily Allowances of Vitamins and Minerals

The Suggested Optimal Daily Nutritional Allowances (SONAS)

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