Recommended Dietary Allowances (RDAs)

For many years the National Research Council of the United States National Academy of Sciences has taken responsibility for establishing guidelines on what quantities of the various nutrients should be eaten by human males and females at various ages. These were called RDAs (for Recommended Dietary Allowances, and often referred to as Recommended Daily Allowances).

However, on August 13, 1997, the Institute of Medicine of the National Academy published a report that: As their findings trickle in, here is a table of RDAs (or AIs) for young adult women and men.
FemalesMalesFemalesMales
Protein50 g63 g Folacin400 µgsame
Vitamin A (retinol)700 µg*900 µg* Biotin30 µg (AI)same
Thiamine (Vitamin B1)1.1 mg1.2 mg Calcium1000 mg (AI)same
Riboflavin (Vitamin B2)1.1 mg1.3 mg Phosphorus700 mgsame
Niacin (Vitamin B3)14 mg16 mg Selenium55 µg70 µg
Pantothenic acid (Vitamin B5)5 mg (AI)same Iron18 mg10 mg
Vitamin B61.3 mgsame Zinc8 mg15 mg
Vitamin B122.4 µgsame Magnesium310 mg400 mg
Vitamin C75 mg* 90 mg* Iodine150 µgsame
Vitamin D5 µg (AI)**same Fluoride3 mg4 mg
Vitamin E15 mg**same Potassium2 gsame
*This value has recently been lowered following the publication of data indicating that a high intake of retinol in older people leads to an increased risk of hip fractures. Vitamin A stimulates osteoclasts, the cells that degrade bone, and inhibits osteoblasts, the cells that build bone. To the extent that the vitamin A requirement is met by ingested beta-carotene, these amounts should be multiplied by 6. And that is probably the best way to get your vitamin A as the body only converts enough beta-carotene into vitamin A to meet its needs. In short, probably no one should consume vitamin tablets containing vitamin A (those with beta-carotene are fine).
*Smokers should add 35 mg to these values.
**5 µg = 200 IU ("International Units").
**The upper limit (UL) is 1,000 mg/day.

Some nutritionists think that the allowances for vitamins C and D are too low.

There is also evidence that beta-carotene has important functions besides being the precursor of vitamin A and therefore should be ingested in amounts greater than needed to meet the vitamin A requirement. In fact, this is probably the best way to secure a safe amount of vitamin A. Several studies have shown that in affluent countries, ingesting vitamin A from vitamin supplements and fortified food in amounts that are even slightly above the RDA lead to an increased risk of bone fractures later in life.

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16 March 2005