Are you taking the right vitamins? Everything you need to know about supplements — from what to avoid to how much you really need - Nutrition

A multivitamin's ingredients can be as daunting to puzzle through as a tax form. With a jumble of numbers and unpronounceable names -- pyridoxine, cobalamin and molybdenum, say -- it's hard to know which ingredients are hype and which you really need to stay healthy.

The most important vitamins are: A, [B.sub.1], [B.sub.2], [B.sub.3] (niacin), [B.sub.6], [B.sub.12], folic acid, C, D, and K, says Bonnie Liebman, nutrition director at the Center for Science in the Public Interest in Washington, D.C. "These vitamins truly are essential for basic bodily functions, such as growth, development, immune functioning and converting food to energy," she says. "For most of us with our fast-paced, hold-the-calories lifestyle, it's just not possible to get enough of them in food on a daily basis, which makes taking vitamins crucial."

In addition to these key vitamins, you also need 100 percent of the Recommended Dietary Allowance (RDA) of copper, zinc and iron. "You can't expect to find that much magnesium or calcium [in a supplement], because you can't get a day's worth to fit in one pill," says Liebman. So you'll want to get your magnesium and calcium in a separate supplement: 1,000 milligrams a day of calcium and 400 milligrams of magnesium.

Your best bet is to choose a multivitamin and multi-mineral formula with 100 percent of the Daily Value (the most conservative guideline) of all ingredients. Add to that a calcium/magnesium tablet, and you've bought yourself a very modest form of health insurance.

The dangers of overdosing

However, as with any nutrient, you don't want to go overboard: Too much of a good thing can be harmful. Indeed, some minerals, such as selenium, zinc and iron, can be dangerous in high levels. The jury's still out on others, because "ethical conditions limit research on humans," says Bob Cousins, Ph.D., a University of Florida biochemist. "As a result, many nutritional supplements have never been tested in well-controlled trials. The long-term effects are unknown." Most multivitamins contain 100 percent of the RDA for iron and zinc, which is generally considered safe, but you shouldn't supplement beyond that for prolonged periods without a doctor's guidance.

And not all ingredients are essential. "It's often the marketing, not the research, department that designs the vitamins," Liebman says. "People think more is better, so manufacturers may throw in things that look good, not because you necessarily need them." Trace minerals that are already more than adequate in most diets include phosphorus, iodine, manganese, chloride, molybdenum and boron. Biotin and pantothenic acid, both B vitamins, also are covered by most diets.

Your supplement also need not contain the antioxidant coenzyme Q-10, which, when it is included, is probably present in too small an amount to be effective for cardiovascular benefits anyway. Also skippable are the minerals nickel, silicon, tin and vanadium (for more on vanadium, see "Can Supplements Make You Thinner?" on page 137). Says Liebman: "It's not clear they're needed by humans at all."

How to be supplement-savvy

Stick to the numbers, not the promises. Since vitamins aren't regulated by the federal government, there are no agreed-upon standards to back up claims like "high potency," "maximum," "mega," "super potency," "stress formula" and "women's formula." That's not to say such formulas aren't worth the money -- you need to check the ingredients to be sure. And don't bother avoiding sugar, starch or color, says Jeffrey Blumberg, Ph.D., a nutrition professor at Tufts University in Boston. "Unless you have a very rare allergy to food additives, like starch or colorings, I know of no value [to be gotten from avoiding them]. What additive-free brands do bring with them is a premium price."

One claim, though, is important to all supplements: Bottles should be marked USP (U.S. Pharmacopoeia), the industry's own seal of approval. This shows that the body absorbs the ingredients well. The USP also requires manufacturers to provide an expiration date.

The ups and downs of the RDAs

The RDAs were first established in 1941 by the National Academy of Sciences (NAS). In 1989, they were partially revised. Since then, they have been adjusted as needed to reflect the most current research findings, says Sandy Schlicker, Ph.D., senior program officer, Food and Nutrition Board with NAS.

For example, in recent years, NAS has revised RDAs for B vitamins, antioxidants and micronutrients; it has increased the RDAs for calcium and vitamin C, and reduced the RDAs for iron and zinc, says Jo Ann S. Carson, Ph.D., R.D., L.D., associate professor of clinical nutrition with the Southwestern Medical Center in Dallas. When all revisions are complete, the RDAs will be known officially as RDIs (Recommended Dietary Intakes).

Some nutrients have Adequate Intakes, which are used when there isn't enough data to establish an RDA. Daily Values, a term established by the Food and Drug Administration, are simply the old Recommended Dietary Allowances.