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
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
"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.