For many years the Food and Nutrition Board 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). They provide the data on which food labels are based. In 1997, the Institute of Medicine of the National Academy published a report that added three new categories, including:
- adequate intake ("AI"), where no RDA has been established
- tolerable upper intake levels ("UL"), to caution against excess intake of nutrients — like vitamin D — that can be harmful in large amounts.
As their findings trickle in, here is a table of RDAs (or AIs) for young adult women and men.
|Protein||46 g||56 g||Folacin||400 µg||same|
|Vitamin A (retinol)||700 µg*||900 µg*||Biotin||30 µg (AI)||same|
|Thiamine (Vitamin B1)||1.1 mg||1.2 mg||Calcium||1000 mg (AI)||same|
|Riboflavin (Vitamin B2)||1.1 mg||1.3 mg||Phosphorus||700 mg||same|
|Niacin (Vitamin B3)||14 mg||16 mg||Selenium||55 µg||same|
|Pantothenic acid (Vitamin B5)||5 mg (AI)||same||Iron||18 mg||8 mg|
|Vitamin B6||1.3 mg||same||Zinc||8 mg||11 mg|
|Vitamin B12||2.4 µg||same||Magnesium||310 mg||400 mg|
|Vitamin C||75 mg*||90 mg*||Iodine||150 µg||same|
|Vitamin D||15 µg **||same||Fluoride||3 mg (AI)||4 mg (AI)|
|Vitamin E||15 mg**||same||Linoleic acid||12 g (AI)||17 g (AI)|
|Vitamin K||90 µg (AI)||120 µg||α-Linolenic acid||1.1 g (AI)||1.6 g (AI)|
*This value has been questioned following the publication of data indicating that a high intake of vitamin A 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 12. 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. There is also evidence that beta-carotene has important functions besides being the precursor of vitamin A and therefore should be ingested in amounts even greater than needed to meet the vitamin A requirement. In short, one should consume vitamin tablets containing beta-carotene and not vitamin A.
*Smokers should add 35 mg to these values, and some nutritionists believe that 200 mg of vitamin C per day is probably optimal for everyone. This is more than twice the current RDA, but far lower than the 2,000 mg/day that is the upper limit (UL) and that some people exceed in the hope of warding off colds, cancer, etc.
**15 µg = 600 IU ("International Units").
**The upper limit (UL) is 1,000 mg/day.