The health perks of eating your vegetables may include a lower risk of lung cancer, new research shows.

The finding, published in The Journal of the American Medical Association, isn’t written in stone. More work is needed to check the results, write Matthew Schabath, PhD, and colleagues.

Schabath works at the University of Texas M.D. Anderson Cancer Center.

Broccoli May Fight Lung Cancer

Preventing Lung Cancer

Quitting smoking is the best way to prevent lung cancer, states the editorial.

Meanwhile, eating a diet rich in fruits, vegetables, whole grains, legumes, and other plant-based products may help.

“Patients should be informed that they may further reduce their risk of developing cancer by adopting a diet rich in fruits and vegetables,” states the editorial.

The editorialists included Lawrence Dacey, MD, MS. Dacey works in the departments of surgery and community and family medicine at New Hampshire’s Dartmouth-Hitchcock Medical Center.

Screening, Treating and Surviving Lung Cancer

Lung Cancer, Diet Studied

Schabath’s study included more than 1,600 lung cancer patients and compared them with more than 1,700 people without lung cancer.

Participants were asked about their diets in the year before lung cancer diagnosis or in the year before the study (if they didn’t have lung cancer).

Special attention was paid to foods including soy, beans, broccoli, spinach, carrots, tea, and rye. Those items include natural compounds called phytoestrogens.

Phytoestrogens have “weak estrogen-like activity,” write Schabath and colleagues.

The scientists had previously found lower lung cancer risk for women who reported using hormone therapy. They wanted to see if the same was true for phytoestrogens.

Cancer Prevention: What Really Works?

Smokers, Nonsmokers Included

Some lung cancer patients have never smoked cigarettes, and not all smokers develop lung cancer. So smoking habits were noted.

People were called “ever smokers” if they had smoked at least 100 cigarettes in their lifetime.

Former smokers were those who had quit smoking at least a year before being diagnosed with lung cancer or before the study was done.

Most people — with or without lung cancer — were former smokers. Current smokers came in second. Few people were nonsmokers.

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Study’s Results

The study showed that overall, the people who consumed the highest amount of phytoestrogens from food had nearly half the lung cancer risk as those with the lowest phytoestrogen intake from food.

The pattern was strongest in nonsmokers. It was also seen in current smokers, but less so in former smokers, the researchers report.

Findings Differed for Men, Women

Men’s lung cancer risk was lower for all three types of plant compounds that were studied.

That included two types of phytoestrogens (isoflavones and lignans), as well as phytosterols, a similar type of plant compound linked to vegetable oils, margarines, spreads, grains, and certain fruits and vegetables.

However, women’s lung cancer risk dropped most when the researchers looked at the big picture of all three plant compounds, not the specific plant compounds studied.

Women who consumed a lot of phytoestrogens and also took hormone therapy had fewer cases of lung cancer than those not taking hormone therapy, the study shows.

Study’s Limits

Lots of factors can affect a person’s cancer risk. This study doesn’t claim to have all the answers, and diet’s role has been debated.

For instance, a 2003 study from the Netherlands showed that eating lots of phytoestrogens may not prevent breast cancer.

People don’t always perfectly recall their diets. No one was told to eat certain foods to try to prevent lung cancer. That’s partly why the researchers call for more work on the topic.

Education, body mass index (BMI), and income were taken into account. Supplement use, family history of cancer, exercise, and alcohol use weren’t noted.

Food Guide

The American Cancer Society recommends eating a variety of healthful foods, especially plant-based foods. That includes consuming at least five daily servings of various vegetables and fruits and choosing whole grains over processed (refined) grains or sugars.

Curious about the foods and plant compounds in Schabath’s study? Items included:

—Snow peas

—Black-eyed peas

—Kidney beans

—Tofu

—Tea (black or green)

—Coffee

—Broccoli

—Carrots

—Dark breads

—Vegetable oil

—Salads made with lettuce

—Strawberries

—Flaxseed

—Onions

—Shakes that contained isoflavones

Coffee and teas watered down the results a bit. When these drinks were included, lung cancer risk was 24 percent lower for people with the highest intake of all phytoestrogens combined, compared to 46 percent lower for those with the highest phytoestrogen intake from food sources alone.

By Miranda Hitti, reviewed by Louise Chang, MD

SOURCES: Schabath, M. The Journal of the American Medical Association, Sept. 28, 2005; vol 294: pp 1493-1504. Dacey, L. The Journal of the American Medical Association, Sept. 28, 2005; vol 294: pp 1550-1551. WebMD Feature: “Cancer Prevention: What Works?” WebMD Medical News: “Phytoestrogens May Not Prevent Breast Cancer.” American Cancer Society, “Prevention & Early Detection: At a Glance — Nutrition and Physical Activities.” News release, JAMA/Archives.