NAS Guidelines for the RDA
The National Academy of Sciences (NAS) has, for many years, set the Recommended Dietary Allowances (RDAs) for many nutrients. The latest version of the RDAs was published in 1989. Since then, use of Dietary Reference Intakes, adequate intake levels and tolerable upper intake levels have more commonly been used when setting dietary standards.
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Units of Measurement
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When calculating RDA for an individual nutrient, it is important to remember that different nutrients employ different units of measurement. For instance, individuals need 700 micrograms of Vitamin A but 2.5 milligrams of Vitamin B1 (thiamin).
Gender Differences
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When first introduced, RDAs were meant for all people. Subsequent research has produced different RDAs for women and men due to their different nutritional needs and body shapes and sizes.
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Age
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Another variable that affects the RDAs is a person's age. Children and infants need significantly smaller amounts of certain nutrients due to their smaller size. For most nutrients, the RDA for children between 4 and 8 is about half of the RDA for adult females.
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References
Resources
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