A daily multiple vitamin may slightly reduce cancer risk in older men, a new study suggests. Many studies have found no benefit from high doses of single vitamins. But the new study looked instead at standard multivitamins. The study included 14,641 male doctors age 50 or older. They were randomly divided into groups. One group took a daily multiple vitamin. The other group took a placebo, or fake pill. After an average of 11 years, researchers compared cancer rates. Men who took the multivitamin were 8% less likely to be diagnosed with a new cancer than those who took the placebo. About half of the cancers were in the prostate. Most of them were early stage, with high odds of survival. There was also little difference in prostate cancer rates between the two groups. So researchers decided to look just at other cancers. Men who took vitamins were 12% less likely to develop the other cancers than those who took the placebo pills. Study results were presented at a cancer conference. Reuters Health news service wrote about it October 17.

By Howard LeWine, M.D.
Harvard Medical School

What Is the Doctor's Reaction?

For many years I recommended a daily multiple vitamin for everyone. My main reason was to help ensure that my patients received at least the minimum amount of vitamins and minerals.

More recently I backed off from this general advice. For healthy people eating a well-balanced diet, the evidence didn't show an added health benefit from a daily multi-vitamin. More and more studies also have shown that high doses of some vitamins, such as vitamin E, might actually cause harm.

I was never concerned that the amounts contained in standard (not high-dose) multiple vitamins were dangerous. And cost was not an issue for most people. Standard products are quite reasonable, especially the generic versions.

But I just couldn't justify advising something without medical evidence to support its use. Until now, I also would not have believed that multiple vitamins might prevent cancer in otherwise healthy people. But the results of this study suggest they might.

The study is the longest randomized controlled trial of a daily multiple vitamin. This type of study is considered the most valid. People who are otherwise similar are randomly divided into groups. One group receives the treatment that is being tested. The other group receives a placebo. Usually this is a pill that contains no medicine.

People who took part in this study were male doctors. They were at least 50 years old when they entered the study. The researchers followed what happened to their health during the next 11 to 14 years.

There were about 8% fewer cancers in men who took a multiple vitamin than in those who took a placebo.

Not surprisingly, more than half of the cancers diagnosed were prostate cancers. PSA testing became very popular during the last 20 years. Like most new prostate cancers diagnosed, the prostate cancers in the study doctors were low-grade cancers with an excellent prognosis.

Interestingly, there was little difference in the rates of prostate cancer between the men who took multiple vitamins and those who didn't. So the researchers subtracted the number of prostate cancers from the total number of cancers. They looked only at cancers that were more likely to cause death or affect quality of life. Rates of these cancers were significantly lower for men who took a multiple vitamin than for those who took a placebo. But no particular type of cancer stood out.

What Changes Can I Make Now?

Don't make the mistake of thinking a multiple vitamin is a good substitute for a healthy diet, or for regular exercise. It's not. A multiple vitamin contains only a small fraction of the healthful substances found in fruits, vegetables and other foods in a healthy diet.

But if you are a man age 50 or over, it is reasonable to take a multiple vitamin based on this new information. I admit this is only one study. But at least I have some evidence to support my view.

What if you are a woman or a younger man? The main reasons for taking a multiple vitamin have not changed. You should take a multiple vitamin if:

• You are concerned that your diet does not provide enough vitamins and minerals.
• You are a woman in your child-bearing years. Each multiple vitamin has 400 micrograms of folic acid. Folic acid helps prevent pregnant women from having a baby with a spine abnormality.
• You spend almost no time in the sun. Except for foods and drinks enhanced with vitamin D, even healthy diets rarely provide enough of this vitamin.

What Can I Expect Looking to the Future?

We will soon learn more from this same study. Further results will include what, if any, benefits a daily multiple vitamin had on heart disease, stroke, eye health, memory and thinking.