How to read a vitamin label.

Here's what you'll find in the best-selling multivitamin, Centrum, which is often imitated by cheaper "store brands " with names like "Central-Vite" or "Century-Vite." Centrum is a "Best Bite" for premenopausal women, but probably has too much iron for men and postmenopausal women. We use it to explain what to look for (or avoid) in your multi.

Vitamin A. There's no need to get more than the Daily, Value (5,000 IU) of vitamin A. But some multis go up to 10,000 IU. They don't go above 10,000 IU to avoid increasing the risk of birth defects in fetuses and toxicity in adults.

Many multis also contain beta-carotene, which the body converts to vitamin A. Trials are under way to find out if beta-carotene helps prevent cancer, heart disease, and cataracts. It doesn't cause birth defects, so it doesn't count towards the 10,000 IU limit it on vitamin A. But high doses may make it harder to absorb other carotenoids that prevent disease. Our advice: don't get more than 15,000 IU of beta-carotene from a pill (Centrum has 2,000 IU - that's 40% of 5,000). Instead, load up on carotene-rich fruits and vegetables.

Vitamin D. It helps you absorb calcium. Yet many older people get too little D from their food - the major sources are milk, fatty fish, and fortified cereals - or from sunshine, especially in the winter. Look for 400 IU, but no more, since too much D is toxic.

Folic Acid. Look for 400 mcg (0.4 mg) to reduce the risk of birth defects (for women who could become pregnant) and possibly heart disease or colon cancer (for everyone). Some good food sources: orange juice, beans, veggies, and fruit.

Biotin and Pantothenic Acid. Ignore these two. You'd have to eat a bizarre diet to run short of either.

Calcium. To reduce the risk of osteoporosis, shoot for a daily dose of 1,000 mg (women or men aged 25 and older) or 1,500 mg (postmenopausal women who don't take estrogen). If you don't get that much from your food, it's cheaper to take a separate calcium tablet than to try to get it all in a multi. Calcium carbonate (in products like Tums, Caltrate, and Os-Cal) has the most calcium per tablet. Try calcium citrate (in a brand like Citracal) if calcium carbonate makes you constipated. Some good food sources: low-fat milk, yogurt, and cheese.

Phosphorus. Look for no more than about 100 mg, but the less you get in your multi, the better. Too much may weaken your bones, and we already get more phosphorus than we need from our food.

Iodine, Manganese, Boron, Molybdenum, and Chloride. Ignore. There's no evidence that people need more than what they get from their food.

Nickel, Tin, Silicon, and Vanadium. Ignore. It's not clear that they're needed by humans at all.

Expiration Date. Look for a supplement that has one...and make sure that the date is at least a few months away.

Each Tablet Contains. Watch out. Some brands list the amount of vitamins and minerals in a "serving," but you need two or three servings a day.

% Daily Value. It's often written as "%DV." it means the same as "% USRDA" (U.S. Recommended Daily Allowance). Labels use them interchangeably.

Vitamin C. Most people need 250 to 500 mg to saturate their bodies' tissues. if you follow the National Cancer Institute's advice to eat five to nine servings of fruits and vegetables a day - or drink at least 2 1/2 glasses of orange juice - you should get that much. if you want to try to get over your colds sooner, you'll need 1,000 mg to 3,000 mg a day - probably from a separate pill. Note: An estimated one in ten people who take 500 to 2,000 mg at one time gets diarrhea.

Vitamin E. Studies are under way to see if high doses (100 to 400 IU or more a day) reduce the risk of heart disease, cancer, and cataracts. You can't get that much from your food - or from most multis - so a separate supplement is worth considering. But there's no guarantee of safety: one large study suggested that 50 IU of E a day might increase the risk of hemorrhagic strokes.

Thiamin, Riboflavin, Niacin, and B-6. While there's no reason to get more than the Daily Value for these B-vitamins, the high doses found in some multis are harmless. Fortunately, none of the multis we looked at came close to the super-high doses of niacin (about 500 mg a day) that may cause liver damage, or the 100 mg or more a day of B-6 that could cause (reversible) neurological problems.

Vitamin B-12. To correct B-12 deficiencies (which folic acid can cover up), older people should take 500 mcg a day (see Sept. 1995, cover story). They'll need a separate supplement. Vegans (who eat no meat or dairy products) should make sure they get the Daily Value (6 mcg). A B-12 deficiency can cause irreversible nerve damage.

Iron. To play it safe, men and postmenopausal women should look for zero or, at most, 10 mg in their multis (see page 6). The Daily Value (18 mg) is okay for premenopausal women, but there's no reason to take more unless your doctor says so.

Magnesium. Some researchers think that Americans get too little from sources like whole grains and beans. Look for at least 100 mg, just for insurance.

Zinc and Copper. Look for the Daily Value, but no more, of each - just for insurance. More than 50 mg of zinc may suppress your antioxidant defenses.

Potassium. Ignore. Amounts in multis are trivial. Instead, eat plenty of fruits and vegetables to help keep your blood pressure from rising with age.

Vitamin K. Women should get 65 mcg a day, while men need 80 mcg. Leafy greens are the best sources. It was so hard to find even 25 mcg in most multivitamins that we didn't make it a criteria for our "Best Bites." Vitamin K may help strengthen bones. But since it also helps blood to clot, K can interfere with anti-coagulant drugs like Coumadin. If you're on them, check with your doctor before taking any vitamin K.

Selenium. So far, most human studies haven't confirmed the theory that selenium can lower the risk of cancer. The RDAs are 55 mcg for women and 70 mcg for men. Caution: Don't take more than 200 mcg. Selenium is toxic, possibly in doses as low as 1,000 mcg.

Chromium. Look for at least 25 to 50 mcg to (possibly) reduce your risk of adult-onset diabetes. There's no need to exceed 200 mcg a day.