Table 3-1 shows the most recent RDAs for vitamins for healthy adults; Table 3-2 shows RDAs for minerals for healthy adults. Where no RDA is given, an AI is indicated by an asterisk (*) by the column heading.
REVIEWING TERMS USED TO DESCRIBE NUTRIENT RECOMMENDATIONS
Nutrient listings use the metric system. RDAs for protein are listed in grams. The RDA and AIs for vitamins and minerals are shown in milligrams (mg) and micrograms (mcg). A milligram is 1/1000 of a gram; a microgram is 1/1000 of a milligram.
Vitamin A, vitamin D, and vitamin E are special cases. For instance, one form of vitamin A is preformed vitamin A, a form of the nutrient that your body can use right away. Preformed vitamin A, known as retinol, is found in food from animals — liver, milk, and eggs. Carotenoids (red or yellow pigments in plants) also provide vitamin A. But to get vitamin A from carotenoids, your body has to convert the pigments to chemicals similar to retinol. Because retinol is a ready-made nutrient, the RDA for vitamin A is listed in units called retinol equivalents (RE). One microgram (mcg) RE is approximately equal to 3.33 international units (IU, the former unit of measurement for vitamin A).
Vitamin D consists of three compounds: vitamin D1, vitamin D2, and vitamin D3. Cholecalciferol, the chemical name for vitamin D3, is the most active of the three, so the RDA for vitamin D is measured in equivalents of cholecalciferol.
Your body gets vitamin E from two classes of chemicals in food: tocopherols and tocotrienols. The compound with the greatest vitamin E activity is a tocopherol: alpha-tocopherol. The RDA for vitamin E is measured in milligrams of alpha-tocopherol equivalents (a-TE).
HOW MUCH IS THAT?
Nutrient amounts are measured in various units:
g = gram
mg = milligram = of a gram
mcg = microgram = of a gram
IU = international unit
RE = retinol equivalent = the amount of “true” vitamin A in an IU
a-TE = alpha-tocopherol equivalent = the amount of alpha-tocopherol in a unit of vitamin E
TABLE 3-1 Vitamin RDAs for Healthy Adults
| Age (Years) | Vitamin A (RE/IU)† | Vitamin D (mcg/IU)‡* | Vitamin E (a-TE) | Vitamin K (mcg)* | Vitamin C (mg) |
|---|---|---|---|---|---|
| Males | |||||
| 19–30 | 900/2,970 | 15/600 | 15 | 120 | 90 |
| 31–50 | 900/2,970 | 15/600 | 15 | 120 | 90 |
| 51–70 | 900/2,970 | 15/600 | 15 | 120 | 90 |
| 71 and older | 900/2,970 | 20/800 | 15 | 120 | 90 |
| Females | |||||
| 19–30 | 700/2,310 | 15/600 | 15 | 90 | 75 |
| 31–50 | 700/2,310 | 15/600 | 15 | 90 | 75 |
| 51–70 | 700/2,310 | 15/600 | 15 | 90 | 75 |
| 71 and older | 700/2,310 | 20/900 | 15 | 90 | 75 |
* Adequate Intake (AI)
† The “official” RDA for vitamin A is still 1,000 RE/5,000 IU for a male, 800 RE/4,000 IU for a female who isn’t pregnant or nursing; the lower numbers listed on this chart are the currently recommended levels for adults.
‡ The current recommendations are the amounts required to prevent vitamin D deficiency disease; recent studies suggest that the optimal levels for overall health may actually be higher, in the range of 800–1,000 IU a day.
| Age (years) | Thiamin (Vitamin B1) (mg) | Riboflavin (Vitamin B2) (mg) | Niacin (NE) | Pantothenic acid (mg)* | Vitamin B6 (mg) | Folate (mcg) | Vitamin B12 (mcg) | Biotin (mcg)* |
|---|---|---|---|---|---|---|---|---|
| Males |