Yale University public health expert David Katz says research has shown, for example, that 400 iu (international units) or more a day of vitamin E may not only fail to prevent heart disease, but can actually hurt you.

Vitamin A also poses a risk Dr. Katz says, citing a large study that observed people who take the supplement. "There was actually an increases risk of hip fracture with women who had the highest intake of vitamin A," he says. "We've also known that high doses of vitamin A can cause birth defects."

Yale University public health expert Dr. David Katz Dr. Katz says that while vitamin C in food promotes good health, there is no evidence that any mega-dose supplement can prevent colds or cancers. "Perhaps one of the more disturbing things is that if you are taking vitamin C while you are being treated for cancer it might actually help protect the cancer cells from chemotherapy. You just can't assume that taking this when sick is a good idea."

Rather than relying on fistfuls of daily vitamins that may do you no good, Dr. Katz suggests consumers take one daily multi-vitamin. "I consider that an insurance policy to make sure that we get enough of all the vitamins and all the minerals we need for good health."

However, Dr. Katz says eating a well-balanced diet rich in vitamins is still the best defense against disease. New Questions About the Health Benefits of Vitamin Supplements> Article courtesy VOA