Daily Dose: Which Vitamins Help, Harm?

May 1, 2006 — -- It's become a daily ritual -- taking pills to supplement the vitamins, minerals and enzymes in your diet.

Americans spend nearly $9 billon every year on vitamin and mineral supplements in the belief that they can help prevent disease and improve health.

No one questions the value of a daily multivitamin, and yet some experts say additional supplements are unnecessary, and in some cases may be dangerous.

For example:

Instead of improving heart health, vitamin E was shown in one study to increase rates of congestive heart failure. According to the Medical Letter, a nonprofit research group, one study found that long-term use of vitamin E supplements did nothing to prevent cancer or major cardiovascular events -- and may have even increased the risk of heart failure for patients with vascular disease or diabetes. And a cancer study found that patients taking vitamin E while undergoing radiation therapy had a higher rate of cancer recurrence than patients taking a placebo.

Instead of reducing the risk of lung cancer, beta carotene was found to increase the rate of lung cancer in one study of smokers. Another study found that smokers and asbestos-exposed workers, when given doses of beta carotene and vitamin A, had an increased risk of lung cancer, death from cardiovascular disease and overall mortality. The rate of death was so high that the study was stopped early.

And another study showed that too much vitamin A from supplements and food increased postmenopausal women's risk of hip fractures. Another study found that a high intake of vitamin A was associated with birth defects when taken during early pregnancy.

Even calcium, which is encouraged in large amounts as women get older, can be dangerous. The Women's Health Initiative, though it found calcium and vitamin D can lower the risk of hip fractures in women over 60, also found that women taking calcium were at a higher risk for kidney stones.

One woman we spoke with, Arlene Freedman, was taking calcium supplements while also eating a diet rich in calcium. Then a routine blood test revealed all these sources of calcium were too much .

Her doctor told her that she no longer needed calcium supplements.

"The good news is you don't need calcium supplements. The calcium supplements were raising your calcium and that's what we don't want," said Dr. Michael Freedman. "As calcium goes very high, it can interfere with your brain's ability to think and is actually one of the causes of dementia."