Smoking Plus Beta-Carotene May Up Cancer Odds

Sept. 20, 2005 -- The nutrient beta-carotene may affect smoking and nonsmoking women differently, French researchers report.

Beta-carotene is a source of vitamin A. It's found in lots of fruits and vegetables, as well as in vitamin supplements.

In the French study, high beta-carotene intake (from foods or supplements) was linked to low levels of cancer in nonsmoking women and high levels of the same cancers in womenhigh levels of the same cancers in women who smoke.

Study: Keep Eating Fruits, Veggies

Why did smokers and nonsmokers show such different patterns? The answer isn't clear.

Smoking and high doses of beta-carotene may gang up to raise cancer risk, but more studies are needed to find out, write the researchers.

Meanwhile, they urge everyone to keep eating fruits and vegetables.

"There is no evidence that smokers should avoid consuming beta-carotene-rich foods such as fruits and vegetables," write Marie-Christine Boutron-Ruault, MD, and colleagues.

Boutron-Ruault works for INSERM, France's national health and medical research agency. The study appears in the Journal of the National Cancer Institute.

The bottom line: The study shows no reason to change recommendations to eat five to nine daily servings of fruits and vegetables as advised by the U.S. National Cancer Institute.

Study's Design

The French study included nearly 60,000 women. In 1994, the women completed questionnaires about the foods they ate, the supplements they took, and their smoking habits. They were in their mid-40s to late 60s at the time.

Over the next seven years or so, 700 women had developed cancers including those of the lung, thyroid, ovaries, cervix, colon, and rectum.

"We investigated all cancers for which any association with tobacco has been suggested for cancer itself," write the researchers.

Then, the scientists reviewed beta-carotene intake and cancer risk for smokers and nonsmokers.

Second Opinion

The results are "quite provocative" but have some limitations, notes a journal editorial.

The editorial comes from Susan Mayne, PhD, FACE, of Yale University's medical school and Scott Lippman, MD, of the University of Texas M.D. Anderson Cancer Center in Houston.

The editorial makes several points about the French study:

• Not all of the cancers on the list have clearly been linked to tobacco.
• Only 2% of participants reported using beta-carotene supplements.
• Doses of beta-carotene supplements weren't reported.
• Beta-carotene is more available to the body from supplements, not foods.

Still, future nutritional studies should note smoking habits, write Mayne and Lippman.

They agree with the French researchers that fruits and vegetables are vital for smokers and nonsmokers alike.

"No evidence shows that higher fruit and vegetable intake increases cancer risk, even in smokers," they write. The heart benefits of nutrients in fruits and vegetables might actually be greater in smokers, they note.

"Therefore, the new research on the interaction between nutrients and smoking should not alter our current policy recommendations with regard to nutrients and cancer risk," states the editorial.

Quitting smoking, losing extra pounds, getting at least 30 minutes of moderate physical activity five or more days per week, and going for recommended checkups are also widely recommended for a healthy lifestyle.

SOURCES: Touvier, M. Journal of the National Cancer Institute, Sept. 21, 2005; vol 97: pp 1338-1344. Mayne, S. Journal of the National Cancer Institute, Sept. 21, 2005; vol 97: pp 1319-1321. National Cancer Institute: "Eat 5 to 9 a Day for Better Health. News release, Journal of the National Cancer Institute.