This article originally appeared in the April 2003 Women’s Health Watch and is provided courtesy of Harvard Health Publications.

The new ABCs of vitamin and mineral intake

The alphabet of essential micronutrients has changed, with important implications for our diet and use of supplements.

Marvel that it is, the body doesn’t manufacture enough of some 40 compounds that it needs for all of its life-sustaining tasks, from building bone, blood, and muscle to regulating brain, liver, and heart function. These essentials—called micronutrients because we need only tiny amounts of them—must come from the food, beverages, and supplements we consume. They include more than two dozen vitamins and minerals.

Official guidance on how much we need of each micronutrient has undergone a shift in emphasis since the federal government issued its first set of Recommended Dietary Allowances (RDAs) some 60 years ago. The original focus was on preventing deficiency diseases, such as scurvy (vitamin C deficiency) and beriberi (vitamin B1 deficiency). Since then, researchers have discovered that certain micronutrients help reduce the risk for major chronic disorders—such as atherosclerosis, cancer, and osteoporosis—if taken in doses higher than are required to prevent deficiency diseases. At the same time, we now know about ailments that can occur when people take overly high doses of supplements.

Changing values, new designations
The Food and Nutrition Board of the National Academy of Sciences’ Institute of Medicine (the government’s adviser on health policy) recently completed a comprehensive new set of nutrient standards called Dietary Reference Intakes (DRIs). These reflect the latest evidence-based research on the links between micronutrients and health and replace the old RDAs.

For the changeover to DRIs, expert panels reexamined and, when necessary, revised the RDAs. If too little was known to establish an RDA, the scientists provided an adequate intake (AI) value. They also designated a tolerable upper intake level (UL), the highest amount of a nutrient deemed likely to have no harmful effects on most healthy people.

DRIs take into account varying nutritional needs by gender and at different stages of life—for example, during pregnancy and lactation, or as we age. As a result, the RDA (or AI) for any one vitamin or mineral may include varying amounts.

Labels: A different matter
You won’t find DRI designations used on food and supplement labels. Instead, labels indicate a percentage of what is called a “daily value” (DV) of a vitamin or mineral. DV is an FDA designation and is the level of intake that the FDA has determined the general American population needs each day. The “% DV” is the percentage of the micronutrient found in one serving.

DVs are not always the same as the new RDAs or AIs. For one thing, the FDA wants to keep labeling simple. It would be impractical, for example, to print multiple values (for pregnant or non-pregnant women, older women, men, and older men) for any one micronutrient. Also, the FDA has not yet updated its DVs to reflect the same new information that the National Academy of Sciences used to establish the DRIs. It plans to do so within the next few years.

The vitamins we need
Vitamins are either water-soluble or fat-soluble. The first group includes vitamin C and the B vitamins. Because water-soluble vitamins don’t store well in the body, we need to consume them on a regular basis. They present little risk of an overdose.

Vitamins in the fat-soluble group—A, D, E, and K—require some fat in the diet to permit them to be absorbed in the intestine. The body stores these vitamins in fat tissues and the liver, so we don’t need to consume them every day. But the one disadvantage of vitamin storage is that harmful levels can build up, especially through supplement use.

A well-balanced diet that includes fruits, vegetables, whole grains, and some dairy products is all that most people need to meet the DRIs. Yet maintaining a high-quality diet can be hard to do. It may be difficult to obtain the RDA of a vitamin through food alone. For example, women of childbearing age may not get adequate folic acid through food to reduce the risk of certain birth defects. And people over 50 may not absorb enough vitamin B12 from food. In light of these concerns, it makes sense to take a standard daily multivitamin as a backup.

See the chart, below, for the new DRIs for vitamins for women. And look for an update on mineral intakes in the May 2003 Harvard Women’s Health Watch.