Tuesday December 14 4:50 PM ET More Evidence Vitamin Does Not Prevent Cancer

More Evidence Vitamin Does Not Prevent Cancer

By Maggie Fox, Health and Science Correspondent

WASHINGTON (Reuters) - Yet another study has struck a blow to the idea that beta-carotene supplements might help prevent cancer, although researchers said this one, published on Tuesday, at least showed they did no harm.

I-Min Lee of Brigham and Women's Hospital in Boston and colleagues examined women taking part in the Women's Health Study. As part of the study, more than 39,000 women aged 45 and up were given beta-carotene, which the body converts to vitamin A; vitamin E; and aspirin -- or dummy pills.

Lee's team looked at the beta-carotene part of the trial, which was stopped after just over two years.

``Among women randomly assigned to receive beta-carotene, there were no statistically significant differences in incidence of cancer, cardiovascular disease or total mortality after a media of 4.1 years,'' they wrote in a report published in the Journal of the National Cancer Institute.

``There was no benefit or harm from beta-carotene supplementation for a limited period on the incidence of cancer and of cardiovascular disease.''

Decades ago, doctors noticed that people who ate the most fruits and vegetables had the lowest risk of cancer and heart disease. They thought that perhaps vitamins might have something to do with this, because they can act as antioxidants, wiping up free radicals -- charged particles that damage cells and cause disease.

Vitamin Results Mixed

The best-known antioxidant vitamins, A, C and E have all been tested to see if people who took them in supplement form might lower their risk of disease.

Results for vitamins C and E are mixed. But several studies suggested that beta-carotene -- which the body converts to vitamin A -- did no good.

And in two studies, one involving 29,000 older Finnish men who smoked, taking supplements of beta-carotene was actually linked with higher rates of lung cancer.

``Clearly, beta-carotene supplements do not prevent cancer,'' James Marshall of the Arizona Cancer Center at the University of Arizona wrote in a commentary.

He said it was not a case of the supplements being ineffective, or of the patients not taking their supplements, because blood tests were used to check. ``The dose more than tripled the blood beta-carotene levels of the experimental subjects,'' he wrote.

Marshall said beta-carotene might be a marker for something else in fruits and vegetables that works to prevent cancer.

``There are thousands of nutrients and hundreds of carotenoids in the foods that we consume,'' he wrote. ``Clearly, focusing as readily as we did on beta-carotene was a mistake.''

Research presented earlier this year at a meeting of the American Association for Cancer Research showed that supplements, from ordinary multivitamins to specially formulated vegetable-based capsules, may slow cancer.

Tomatoes And Prostate Cancer

In one study, a team at the Barbara Ann Karmanos Cancer Institute in Detroit found tomato supplements helped slow prostate cancer in men diagnosed with the disease. Tomatoes are rich in lycopene, an antioxidant related to beta-carotene.

Another recent study suggests that vitamins such as vitamin C might actually help cancer cells survive chemotherapy and radiation.

Dr. David Golde and colleagues at Memorial Sloan-Kettering Cancer Center in New York found cancer cells absorb extra amounts of vitamin C, and may use it to protect themselves from the effects of chemotherapy and radiation.

And a team at the University of North Carolina reported to a meeting of the American Society of Cell Biology in Washington this week that mice which got diets low in vitamins A and E actually had brain tumors that grew more slowly, which they said suggested cancer cells use the vitamins to protect themselves.


Samual M. Rushing
Last modified: Tue Dec 14 16:08:25 PST 1999