Vitamins may increase risk of cancer

Seven's On Call with Dr. Jay Adlersberg
February 28, 2008 9:00:00 PM PST
A lot of people take vitamins to stay healthy. But new research finds some vitamins may actually increase your risk of cancer. Seven's on call with Dr. Jay Adlersberg.

That will be astounding to some who like to think that vitamins are a panacea for illness. But a report the current issue of American Journal of Respiratory and Critical Care Medicine says one antioxidant vitamin may make the risk of cancer higher.

Dr. Andrew Evans is a radiation oncologist who kills cancers with X-rays. But his hardest task may be dealing with lung cancer.

"It is the highest cause of cancer mortality in the US and when it is diagnosed it's very difficult to treat with a poor prognosis," Dr. Evans said.

That poor prognosis was the subject of the study, which looked for any protective effect of vitamins supplements.

"I've heard that vitamin C will do something like that...reduce your risk of cancer," one vitamin taker said. "But I don't know if it works."

Probably not. The study found that multivitamins and vitamin C had no effect on reducing lung cancer risk. Ominously, vitamin E made things worse.

"In a small group of people who supplemented with vitamin e, it actually increased their risk of cancer over the long term," Dr. Evans said.

Smoking causes most lung cancers. Prior studies of vitamin E and beta carotene in smokers found no protection. This is one of the first reports showing a pro-cancer effect of vitamin E.

Smoking produces chemicals called free radicals that damage DNA, which can lead to lung cancer. Vitamin E is an antioxidant and cleans up the radicals.

Not with lung cancer, apparently. The reason is not clear. What is clear is that fresh fruits and vegetables containing these vitamins will reduce cancer risk.

"It not only reduced lung cancer risk, but risk of colorectal cancers, gastric cancers and other cancers as well," Dr. Evans said.

Vitamin pills are intended to prevent or treat vitamin deficiencies. They were never meant to treat disease. A vitamin industry group made the point that preventing cancer is a lot to ask of a vitamin pill.

The best way to prevent lung cancer is never to start smoking. And if you smoke, you should quit.