More veggies join fight against lung cancer.

More veggies join fight against lung cancer 

In a dietary survey, epidemiologists have teased out previously unsuspected edible entities that may help prevent lung cancer in humans. The study provides the strongest evidence yet that vegetable constituents other than beta-carotene -- the nutrient focus of almost all previous lung cancer-dietary research -- help protect against the disease, says study leader Loic Le Marchand of the Cancer Research Center of Hawaii in Honolulu.

The most surprising result indicates that routine consumption of all the vegetables listed on the study questionnaire offers stronger protection than consumption of any one kind of vegetable or nutrient. "That suggests to us that we need to look at the additive and interactive effects of these [vegetable] components," Le Marchand says.

The new evidence "will require future investigators to consider that the prime factor in [lung cancer] risk is not necessarily beta-carotene but may be some other constituent of vegetables," says Saxon Graham of the School of Medicine and Biomedical Sciences at the State University of New York at Buffalo. "But it takes a great many [epidemiologic] studies to establish a finding."

Le Marchand and his co-workers also discovered that tomatoes, dark green vegetables and cruciferous vegetables, such as broccoli and cabbage, lower lung cancer risk at least as much as vegetables high in beta-carotene. This suggests that constituents "such as lutein, lycopene, indoles and others may also protect against lung cancer in humans," write the researchers in the Aug. 2 JOURNAL OF THE NATIONAL CANCER INSTITUTE.

No numerical estimates exist for the amounts of lutein and lycopene in foods, so the group based its intake estimates on subjects' consumption of foods known to contain these nutrients. Lutein appears primarily in dark green vegetables; tomatoes represent the chief source of lycopene. Researchers have shown that indoles and other nonnutritive constituents of cruciferous vegetables prevent tumor formation in animals. Cruciferous vegetables have been linked to decreased colon -- but not lung -- cancer risk in humans, Le Marchand says.

His team asked 230 male and 102 female lung cancer patients, as well as a healthy, age-matched group of 597 males and 268 females, about their smoking habits and food, vitamin and alcohol consumption. The researchers determined the lung cancer risk of the 25 percent with the lowest intake of a given food or nutrient and compared that with the risk of the 25 percent with the highest intake. They found high beta-carotene intake associated with a three-fold risk decrease in females and a two-fold decrease in males. Risk was down seven-fold in females and about three-fold in males who ate lots of vegetables in general.

Echoing previous studies, the group found that neither vitamin C nor A seemed to affect lung cancer risk and that fruits (other than tomatoes) seemed to play no protective role.

No vegetable or vegetable group on the questionnaire increased lung cancer risk, but previous studies have shown that other foods high in cholesterol or fat can increase this risk. Thus, Le Marchand suggests, smokers who cannot kick the habit "might want to consider improving their diet."