A recent editorial by Paul Offit provides data that taking more vitamins than your daily requirement is more likely to increase your risk of cancer and death (this has been noted on this blog as well –see related links below).
Here is an excerpt:
…last year, a Cochrane review found that “beta carotene and vitamin E seem to increase mortality, and so may higher doses of vitamin A.”
What explains this connection between supplemental vitamins and increased rates of cancer and mortality? The key word is antioxidants.
Antioxidation vs. oxidation has been billed as a contest between good and evil. It takes place in cellular organelles called mitochondria, where the body converts food to energy — a process that requires oxygen (oxidation). One consequence of oxidation is the generation of atomic scavengers called free radicals (evil). Free radicals can damage DNA, cell membranes and the lining of arteries; not surprisingly, they’ve been linked to aging, cancer and heart disease.
To neutralize free radicals, the body makes antioxidants (good). Antioxidants can also be found in fruits and vegetables, specifically in selenium, beta carotene and vitamins A, C and E. Some studies have shown that people who eat more fruits and vegetables have a lower incidence of cancer and heart disease and live longer. The logic is obvious. If fruits and vegetables contain antioxidants, and people who eat fruits and vegetables are healthier, then people who take supplemental antioxidants should also be healthier. It hasn’t worked out that way.
The likely explanation is that free radicals aren’t as evil as advertised. (In fact, people need them to kill bacteria and eliminate new cancer cells.) And when people take large doses of antioxidants in the form of supplemental vitamins, the balance between free radical production and destruction might tip too much in one direction, causing an unnatural state where the immune system is less able to kill harmful invaders. Researchers call this the antioxidant paradox.
In December 1972, concerned that people were consuming larger and larger quantities of vitamins, the F.D.A. announced a plan to regulate vitamin supplements containing more than 150 percent of the recommended daily allowance. Vitamin makers would now have to prove that these “megavitamins” were safe before selling them. Not surprisingly, the vitamin industry saw this as a threat, and set out to destroy the bill. In the end, it did far more than that.
Industry executives recruited William Proxmire, a Democratic senator from Wisconsin, to introduce a bill preventing the F.D.A. from regulating megavitamins. On Aug. 14, 1974, the hearing began.
Speaking in support of F.D.A. regulation was Marsha Cohen, a lawyer with the Consumers Union. Setting eight cantaloupes in front of her, she said, “You would need to eat eight cantaloupes — a good source of vitamin C — to take in barely 1,000 milligrams of vitamin C. But just these two little pills, easy to swallow, contain the same amount.” She warned that if the legislation passed, “one tablet would contain as much vitamin C as all of these cantaloupes, or even twice, thrice or 20 times that amount. And there would be no protective satiety level.” Ms. Cohen was pointing out the industry’s Achilles’ heel: ingesting large quantities of vitamins is unnatural, the opposite of what manufacturers were promoting.
A little more than a month later, Mr. Proxmire’s bill passed by a vote of 81 to 10. In 1976, it became law. Decades later, Peter Barton Hutt, chief counsel to the F.D.A., wrote that “it was the most humiliating defeat” in the agency’s history.
As a result, consumers don’t know that taking megavitamins could increase their risk of cancer and heart disease and shorten their lives; they don’t know that they have been suffering too much of a good thing for too long.
Paul A. Offit is the chief of the infectious diseases division of the Children’s Hospital of Philadelphia and the author of the forthcoming book “Do You Believe in Magic?: The Sense and Nonsense of Alternative Medicine.”
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