Lung Cancer Health Center

Breathe Easier With Fruits and Veggies

Oct. 9, 2000 -- It's not just what you eat but how long you eat it, researchers say. Evidence is mounting that substances in vegetables can help protect against lung cancer -- if they're eaten for at least four years.

The substances are called carotenoids. They're related to vitamin A and give the red, orange, and yellow color to vegetables such as carrots and tomatoes. There are many different carotenoids, though, and until recently the amounts of the specific compounds in various foods was not known. In addition to vitamin-like activity, carotenoids are antioxidants. Antioxidants are thought to inactivate harmful free radicals -- a natural by-product of daily living that can cause normal cells to turn cancerous. Data from ongoing studies now suggest that the different carotenoids have very different effects on disease prevention.

In this study, which appears in the October issue of the American Journal of Clinical Nutrition, the researchers collected information from 77,000 women and 47,000 men about their diet.

The researchers mailed questionnaires to study participants, asking them how much of particular kinds of foods -- including certain fruits and vegetables -- they ate over the course of a year. Then they followed the participants for 10 years to find out which ones ended up contracting lung cancer.

The researchers found that participants who consumed the highest amounts of fruits and vegetables had a 20% to 25% lower risk of lung cancer compared to those consuming lower amounts. No changes in lung cancer risk were associated either with taking multivitamin supplements or with taking beta-carotene, one of the more popular carotenoid supplements. In addition, carotenoids in food had to be consumed for at least four years before a definite effect was found.

"The message from our study is that it's not just one carotenoid, but a variety of carotenoids that appear to reduce the risk of lung cancer, says Dominique Michaud, ScD, the study's lead author. "Our message is to support the current recommendations for people to eat a wide range of fruits and vegetables instead of focusing on supplements for things like beta-carotene." Michaud is an instructor of medicine at the Channing Laboratory at Brigham and Women's Hospital in Boston.

In addition to beta-carotene, the study also included four other carotenoids: alpha-carotene, lutein, lycopene, and beta-cryptoxanthin. Alpha-carotene is found mostly in carrots, lutein is found in green, leafy vegetables such as spinach and kale, lycopene is found in tomatoes, and beta-cryptoxanthin is found mostly in oranges. "Beta-carotene is found in carrots, but also a lot of other vegetables as well -- you get a little of it from a lot of different vegetables," says Michaud.

Although many people take beta-carotene supplements, "if anything, the association [with reduced lung cancer risk] was stronger for alpha-carotene than beta-carotene," she notes. For instance, among nonsmokers, those who ate the most fruits and vegetables containing alpha-carotene had a 63% decrease in lung cancer risk compared to those who ate the least of these foods.