Some Vitamins Can Do More Harm Than Good

March 21, 2006 — -- Vitamins are big business. Americans spend $7 billion a year on them in hopes of warding off colds, cancer and other diseases. But new studies show that high doses often provide no health benefit and can even cause harm.

"The most consistent finding we are seeing in the research is a lack of any medical benefits," said Dr. David Katz, "Good Morning America's" medical contributor and associate professor adjunct in public health practice at Yale University.

"Many people take high doses of vitamins to fight off colds, cancer, heart disease. And over and over again, we've looked for the active ingredient in these vitamins to find out what is working and have been unable to find anything."

Katz said there was a potential danger to megadoses of popular vitamins:

Rather than rely on vitamins, Katz recommends eating a well-balanced diet rich in vitamins, minerals and other nutrients. He also recommended taking a multivitamin.

"When you look at all the literature, it appears that the levels of vitamins in our ancestors' diet was optimal," Katz said. "We can best recreate that by eating a balanced diet supplemented by a multivitamin."