Beta-carotene and cancer: a beneficial antioxidant for non-smokers but harmful for smokers

A high intake of beta-carotene is associated with a decreased risk of tobacco-related cancers among non-smokers, but with an increased risk in smokers, according to a study by the French National Institute of Health and Medical Research ( Inserm), published in the "Journal of the National Cancer Institute" (JNCI).

As part of an epidemiological study of women in the general mutual National Education (E3N), Françoise Clavel-Chapelon Inserm and Institut Gustave Roussy in Villejuif (Val de Marne) and his team studied the relationship between consumption of beta-carotene and risk of tobacco-related cancers (colorectal, thyroid, ovarian, cervical and lung cancer), says the press release issued by Inserm.

So far, some studies have demonstrated a reduced risk of cancer associated with the consumption of beta-carotene while experimental studies have suggested that consumption of high doses of this antioxidant may be associated with an increased risk of lung cancer and digestive smokers.

French researchers analyzed information on diet, taking supplements, and smoking status of nearly 60,000 women from questionnaires distributed in 1994. The women were divided into four groups according to their intake of beta-carotene and were followed for a median of 7.4 years. During this follow-up, 700 women developed a smoking-related cancer.

The Inserm shows that women who had never smoked, the increasing consumption of beta-carotene was inversely associated with the risk of developing cancer. In contrast, among women who smoked during their life-they have stopped or not, the risk of cancer is highest among those with the highest intake of beta-carotene (taking food supplements associated with high food consumption).

In the population of 60 000 women followed, the absolute risk of cancer over ten years is approximately 180 cases per 10,000 women, smokers or not. In case of high beta-carotene consumption, it only amounts to 81.7 cases per 10,000 women in non-smokers, while it reached the value of 368.3 cases per 10,000 women in smokers.

"This study reaffirms the need to examine separately the smokers, former smokers and non-smokers in the analysis of the role of dietary supplements in the prevention of cancer," say U.S. researchers in an editorial accompanying the publication of the article .

"Although beta-carotene is likely to be cocarcinogen, we can not however recommend that smokers avoid consuming foods rich in beta-carotene such as fruits and vegetables in which other components may oppose potentially deleterious interaction between beta-carotene and tobacco, "say the authors of the study in the press release of Inserm.