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Studies Suggest High Doses of Vitamins May Be Dangerous

Posted on: Wednesday, 5 January 2005, 12:00 CST

Could mother -- and conventional wisdom -- have been wrong all these years? For decades, people have popped vitamins in hopes of staving off dreaded diseases including cancer and heart disease, and to boost their defenses against more mundane maladies such as the common cold.

At worst, conventional wisdom says, taking vitamins was a waste of money and surely couldn't hurt you.

But that wisdom is getting turned on its head:

Ten years ago, a study found that beta carotene, which the body uses to make vitamin A, actually increased the risk of lung cancer in smokers despite preliminary studies that hinted at a benefit.

In November a study linked high-doses of vitamin E with increased death rates, which might persuade many people to toss their pills.

Another recent study concluded that antioxidant supplements were of limited benefit in preventing certain cancers.

The studies prompt the question: "Is it time to rethink the way we view vitamins?"

Some physicians say taking a multivitamin might still be a good idea, but the jury is out on vitamin E and other high-dose antioxidant supplements. It's clear, however, that the days of popping supplement pills with abandon are gone.

The controversial vitamin E study was conducted by Johns Hopkins University researchers who pooled data from 19 earlier studies of nearly 136,000 patients.

Their conclusion: Taking vitamin E in excess of 400 international units (the recommended daily allowance is 33 IU) caused 39 additional deaths per 10,000 people, and therefore should be avoided.

Dr. Raymond Burk, a professor of medicine at Vanderbilt University Medical Center who has studied vitamins since the 1970s, says that for years he has waited for a study like this to come out.

"My view all along has been that antioxidants might have some toxicity if you gave them in excess," he says.

In regular doses, antioxidants are thought to protect cells by neutralizing harmful molecules known as free radicals. Some researchers believe that in high doses, antioxidant supplements might disrupt the body's natural balance of antioxidants and increase the body's vulnerability to cell damage.

Critics argue that pooling several older studies that individually weren't definitive doesn't make for convincing results.

Dr. Marshall Johnson, an internist at Family Healthcare of Hendersonville, Tenn., says the results have tempered -- but not extinguished -- his enthusiasm about vitamin E.

"I am certainly not inclined to tell my patients to completely stop taking vitamin E," he says. But "in the past as opposed to recommending between 400 and 800 international units, I am more apt to recommend a dose of 200."

Burk acknowledges the limitations of the Hopkins study and, like Johnson, is withholding a final judgment. But based on the information he does have, "I certainly don't go around now recommending vitamin E or any of these other antioxidants."

Doctors differ on multivitamins

High-dose antioxidant supplements might not be the disease- fighting wonders people thought they were, but that doesn't necessarily mean you should quit taking a daily multivitamin.

If you don't take a multivitamin, however, doctors say you shouldn't worry too much, either.

Dr. Raymond Burk is a professor of medicine at Vanderbilt University Medical Center who studies vitamins. He doesn't take a multivitamin and says healthy adults who eat a balanced diet don't need to either.

If you do choose to take one, remember that the Food and Drug Administration doesn't subject them to the same scrutiny as prescription drugs.

ConsumerLab.com, an independent organization that tests vitamins, supplements and other health products, has found that about 40 percent of multivitamins have problems. These include not having enough of the nutrients listed on the label.

A few, including children's vitamins known as Li'l Critters Gummi Vites, were found to be contaminated with lead.

Some vitamins carry seals from groups such as ConsumerLab.com, United States Pharmacopeia and NSF International that verify the ingredients listed on the label are actually in the bottle and are free from common contaminants. Because most vitamins don't carry seals, ConsumerLab.com president Dr. Tod Cooperman suggests alternating between two different brands of vitamins daily to increase your chances of getting the vitamins you need.

Source: Tulsa World

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