Study: Beta-Carotene Ups Colorectal Cancer Risk for Smokers, Drinkers

Smokers and drinkers who take beta-carotene supplements to help prevent cancer may actually increase their risk of colorectal cancer, according to Dartmouth Medical School researchers.

Reporting on their study in the Journal of the National Cancer Institute, the researchers said beta carotene doubled the risk of recurring adenomas -- benign tumors that could lead to colorectal cancer -- for people who smoked cigarettes and drank more than one alcoholic drink per day.

However, in non-smokers and non-drinkers, beta-carotene reduced the risk of colorectal adenoma recurrence by 44 percent compared to those those taking a placebo.

"The key point of the study was the supplements had different effects, depending on the smoking and drinking habits of the subjects," said Dr. John A. Baron, professor of medicine at Dartmouth.

Beta-carotene, found naturally in fruits and vegetables such as carrots and oranges, has been widely promoted as preventing cancer.

But Baron said the findings illustrate the complexity researchers face in designing successful cancer prevention methods.

In the latest study, researchers followed 864 people who were polyp-free after having had previous intestinal polyps removed. Participants were randomly assigned to receive a placebo, beta-carotene, vitamin C plus vitamin E, or beta-carotene plus vitamins C and E.

"Supplementation [with beta-carotene] was beneficial among subjects who did not drink or smoke but, if anything, increased risk among those who drank and/or smoked," Baron concluded.

Other Sources: Journal of the National Cancer Institute