Study shows Americans have love affair with vitamins

Consumers will be hard-pressed to use the guidelines to make more nutritionally savvy food and supplement purchases. Don't expect food labels to be updated with the new "recommended dietary allowances" any time soon. The Food and Drug Administration hasn't begun considering whether to force vitamin bottles to list the safe upper doses.

It may take questioning a dietitian to learn that more than 1,000 milligrams a day of vitamin E -- or 1,500 international units -- could cause uncontrolled bleeding.

Or that many people over age 50 have trouble absorbing vitamin B12 from natural food sources and thus should eat fortified foods, like breakfast cereals, or a daily supplement to ensure they get 2.4 micrograms a day.

Or that the amount of vitamin D older people need for strong bones has doubled, to 400 international units.

The good news: Once you learn how many nutrients you need, an Agriculture Department Internet site quickly shows how much you're eating.

Munched a handful of almonds? The Web site -- http://www.nal.usda.gov/fnic/foodcomp -- reveals that's 7.5 milligrams of vitamin E, half a day's supply in a single snack.

The Institute of Medicine, a private science organization that sets the nation's RDAs for nutrients, spent four years reviewing the scientific research into vitamins and minerals. Between 1997 and last week, it issued four reports, hundreds of pages each, determining the proper dose of each to optimize health and how much could cause side effects.

Consider vitamin C: Women need 75 milligrams a day, men 90. Smokers should add another 35 milligrams. But more than 2,000 milligrams a day can cause diarrhea.

Dietitians are devouring the reports. No one has issued a consumer-friendly list.

Today's food labels are based on RDAs set in 1968. The FDA won't begin steps to add new vitamin numbers until the institute issues another report next year on how much protein, fat and fiber we also should eat.

Many RDAs haven't changed a lot. So nutritionists say a healthy daily diet, with at least five fruits and vegetables, can provide plenty of most vitamins.

More important: Until FDA updates vitamin supplement labels, nobody will know safe upper doses, even as sales of multivitamins with three times the RDA and larger "megadose" supplements rage.

"You can have too much of a good thing," warns Tufts University nutrition professor Dr. Johanna Dwyer. "The first message is make sure you're not getting too much."

Consider vitamin A. Enough -- 900 micrograms a day for men, 700 for women -- is important for good vision and immune function. But more than 3,000 micrograms daily can risk birth defects in pregnant women, and liver damage for others.

Many vitamin supplements are sold in "international units," very confusing because how to convert IUs into micrograms and milligrams differs from nutrient to nutrient. For vitamin A, the guidelines say a microgram equals 3.33 international units -- so a popular megadose of 10,000 units hits the daily safety limit.

Another big question is how consumers with special needs will learn their new recommended doses, such as older people who should pay attention to vitamins B12 and D. Even updated food labels probably won't have enough space to tell them.

What's a consumer to do?

First, "think about what you're eating," says Dwyer. Try to get most vitamins from food and take only supplements your body really needs. People who don't eat much dairy may need calcium supplements.

Alternatively, using a regular multivitamin with 100 percent of RDAs "is sensible." <