A second study suggests that the perks of eating your fruits and veggies may include a lower chance of developing lung cancer.
Foods rich in plant chemicals called isothiocyanates and quercetin appeared to offer the best protection against lung cancer, the study showed.
Isothiocyanates are found in cruciferous vegetables such as broccoli, cabbage, cauliflower, brussels sprouts, and turnips. Apples, grapes, onions, and broccoli are good sources of quercetin.
Both studies were presented here at the annual meeting of the American Association for Cancer Research.
Exercise Wards Off Breast Cancer
All the women filled out an extensive questionnaire that asked about their diet, smoking, and exercise habits.
Overall, women who engaged in recreational exercise 30 to 150 minutes per week were 50% less likely to have breast cancer than women who exercised less than a half hour per week.
But Hispanic-American, Tunisian-Arab, and Polish-Caucasian women all benefited as well, researcher Teresa Lehman, PhD, of BioServe Biotechnologies in Beltsville, Md., tells WebMD.
The findings held true regardless of whether a woman was premenopausal, perimenopausal, or postmenopausal, she adds.
Exercising more than 150 minutes per week did not confer additional benefit, she adds.
More Exercise May Be Better
Women who exercised 15 minutes or more per session were 40% less likely to have breast cancer, compared with women who exercised less than 15 minutes per session.
The analysis took into account a woman's age, race, and weight as well as how much she smoked in her lifetime -- all factors that can affect breast cancer risk.
Marji McCullough, ScD, RD, of the American Cancer Society, tells WebMD that the findings are consistent with the group's recommendation to engage in physical activity as a means of keeping breast cancer risk down.
But she takes issue with the finding that more is not better.
Women should work out 30 minutes a day, five times a week, to reap the greatest benefits, McCullough says.
"And even more, like 45 minutes a day, and vigorous activities like running, will reduce breast cancer risk even further," McCullough says.
Fruits, Veggies Linked to Lower Lung Cancer Risk
Participants filled out a 58-item questionnaire that asked about their eating habits over the past year.
Compared with people who didn't eat any isothiocyanate-rich foods in an average week, those who consumed five or more servings were 61% less likely to have lung cancer, Lam tells WebMD.
People who ate quercetin-rich foods at least four times a week, on average, were 51% less likely to have lung cancer than those who ate none.
Eating fruits and veggies more than four or five times a week appeared to cut the risk of lung cancer by 42%.
The analysis took into account some factors that can affect lung cancer risk, including weight, alcohol consumption, and smoking history.
Nevertheless, Lam stresses that the study does not prove cause and effect. Further research is needed before any dietary recommendations can be made, she says.
McCullough agrees. She notes that people don't always perfectly recall their diets or how much they used to smoke.
The American Cancer Society recommends eating a variety of healthy foods, especially plant-based foods. That includes consuming at least five daily servings of various fruits and veggies.