Veggies may cut nonsmoker lung cancer risk.

Smokers who can't or won't quit can still reduce their chances of getting lung cancer by eating plenty of fruits and vegetables, researches believe. Now a new study suggests that a diet rich in fresh produce also may protect nonsmokers from this deadly disease.

Cigarette smoking remains the culprit in most cases of lung cancer. Yet this disease also claims the lives of about 22,350 nonsmokers in the United States annually. That toll represents 15 percent of all U.S. lung-cancer deaths.

A few studies previously had looked at dietary factors and the risk of lung cancer among nonsmokers. This research examined risk only among small groups of nonsmoking women. The new study is the largest so far and the first to include men, points out Susan Taylor Mayne, an epidemiologist at the Yale University School of Medicine. Mayne and her colleagues report their findings in the Jan. 5 JOURNAL OF THE NATIONAL CANCER INSTITUTE.

The team recruited 413 lung cancer patients and another 413 men and women who served as controls. All participants in the study were either nonsmokers or had quit smoking at least a decade prior to the study. Researchers asked the volunteers to estimate their usual consumption of 26 different food items. In some cases, a spouse or a close relative answered dietary questions when a lung cancer patient was very ill.

A statistical analysis showed that consumption of raw vegetables and fresh fruits significantly reduced a nonsmoker's change of developing lung cancer. Mayne estimates that, on average, nonsmokers can reduce their lung cancer risk by 40 percent by simply adding one-and-a-half servings of such fruits or veggies to their daily diet.

The National Cancer Institute (NCI) recommends eating live or more servings of fruits and vegetables every day. However, most Americans still fall far short of the dietary goal, Mayne points out.

The new study suggests that fruits and veggies are more potent cancer fighters when raw than when cooked or processed. Extreme temperatures during cooking or processing may destroy certain nutrients -- such as beta carotene -- that provide an antitumor effect, Mayne notes.

The consumption of whole milk increased lung cancer risk, a finding that needs further study. The fat in whole milk may actually cause that added jeopardy, or whole milk may simply identify people with lifestyles that put them at added risk for lung cancer, Mayne says.

In an intriguing twist, the researchers found evidence that nonsmokers were protected from lung cancer when they included cheese in their usual diet. That finding fits with research conducted by Michael W. Pariza at the University of Wisconsin-Madison. Pariza's data suggest that a fatty acid in cheese (conjugated linoleic acid) has antitumor properties (SN: 2/15/92, p.104).

"There's no question that conjugated linoleic acid is a very effective cancer inhibitor in rodent models," Pariza says. What does that mean for humans? "We have no idea," Mayne cautions, adding that her findings on cheese remain very preliminary.