Multiple Choice: How To Pick A Multivitamin

Nutrition Action Healthletter, April, 2000 by Bonnie Liebman

Phosphorus. Unnecessary. Look for no more than 100 mg; the less, the better. Too much may impair calcium absorption, and we already get more phosphorus than we need from our food.

Zinc and Copper. Look for about 15 mg of zinc and 2 mg of copper--that's the DV of each--just for insurance. Too much zinc can impair the absorption of copper, so don't take a multi that only has zinc. More than 50 mg of zinc a day (on top of the 15 mg you get from food) may depress your immune system. Sucking on zinc gluconate lozenges may shorten a cold (possibly by killing cold viruses in the mouth), but taking high daily doses of a zinc supplement won't.

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

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

Lutein. Ignore. In one study, people who consumed roughly 14,000 mcg a day of lutein (and its cousin zeaxanthin), largely from leafy green vegetables, had a lower risk of cataracts than people who consumed roughly 2,000 mcg. But it's not clear that the lutein--rather than something else in the vegetables--is responsible ... or that 250 mcg is enough to matter. Best bet: Eat your spinach.

% 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. While the DV is 60 mg, most people need 250 to 500 mg to saturate their bodies' tissues. If you follow the National Cancer Institute's advice to eat at least five to nine servings of fruits and vegetables a day, you should get that much. To try to get over a cold sooner, you'll need 1,000 mg to 3,000 mg a day--from a separate pill. Taking more than 1,000 mg at one time may cause diarrhea.

Vitamin E. Studies are under way to see if 100 IU to 400 IU a day reduces the risk of cancer and cataracts. In the best study so far, vitamin E didn't protect against heart attacks or strokes (see Quick Studies, p. 4). Some studies suggest that vitamin E (about 50 IU a day) lowers the risk of prostate cancer, but only in smokers. It's tough to get more than the DV (30 IU) from food.

Vitamin K. Vitamin K may help strengthen bones. Women should get 65 mcg a day, while men need 80 mcg. If you eat lots of vegetables, especially leafy greens, you should get enough.

Thiamin (B-1), Riboflavin (B-2), Niacin, and Vitamin B-6. While there's no reason to get more than the DV for these B-vitamins, the high doses found in some multis are harmless. Fortunately, few multis come close to the super-high doses of niacin (about 500 mg a day) that may cause liver damage or the high doses of B-6 (more than 200 mg a day) that can cause (reversible) neurological problems.

Vitamin B-12. To play it safe, people older than 50 should take a multi with at least 25 mcg because they may lack the stomach acid needed to extract B-12 from food. Others should get at least the DV (6 mcg). A B-12 deficiency can cause irreversible nerve damage.