The latest on "unsafe" vitamins

76 million Americans take vitamins. Here's what you can swallow without worry.

In my review of cutting-edge research, I have found this to be the best advice: Don't exceed the doses recommended on supplement labels. If you take more than one supplement, be sure the amounts of a specific nutrient do not total a toxic dose. When using vitamins to treat a particular malady, do so under the supervision of a doctor.

6 TO BE CAUTIOUS ABOUT

1. Vitamin A. It can accumulate in tissue, causing liver damage at a long-term daily dose of 25,000 IU. It has been linked to birth defects at over 10,000 IU daily.

2. Vitamin D. It can build up in fat tissues and harm the liver. In most adults, the toxic dose is over 50,000 IU a day. Children can be poisoned by as little as 2,000 IU daily.

3. Selenium. Too much can harm the liver, nervous system, skin, nails and teeth. Just 600 micrograms a day might be harmful. Don't take more than 200mcg daily in a supplement.

4. Vitamin B6. Excessive longtime use can cause neurological problems, such as numb limbs. Symptoms usually disappear after vitamins are stopped. Many supplements contain B6, so add up your dosages to avoid a toxic level. Consult a doctor if you use high doses therapeutically.

5. Zinc. Doses over 60 milligrams can interfere with the use of copper, lowering your antioxidant defenses; damage immunity; and harm arteries by skewing the ratio of good to bad cholesterol.

6. Niacin. Just 10mg of nicotinic acid (but not nicotinamide) can cause flushing. More than 1,000mg can cause diarrhea, nausea and liver damage. Most dangerous if improperly used: slow-release nicotinic acid, sometimes used to improve cholesterol. Take it only under a doctor's supervision.

Regardless of reports you may have heard, top scientists tell me these important supplements are generally safe:

1. Vitamin C. Don't credit reports that taking 500-1,000mg promotes chronic diseases, say U.S. antioxidant authorities.

2. Vitamin E. The most common type of vitamin E in supplements, alpha tocopherol, is, in fact, not dangerous.

3. Beta carotene. There's no evidence of danger to non-smokers, but in smokers, especially those who drink heavily, beta carotene seems to promote lung cancer.

4. Calcium. Contrary to popular belief, calcium and vitamin C may help retard -- not promote -- kidney stone growth.