Eating legumes at least three times a week and brown rice at least once a week was linked to a reduced risk of colon polyps by 33 percent and 40 percent respectively, according to Loma Linda University research recently published in Nutrition and Cancer. High consumption of cooked green vegetables and dried fruit was also associated with greater protection, the study shows.
"Eating these foods is likely to decrease your risk for colon polyps, which would in turn decrease your risk for colorectal cancer," says lead author Yessenia Tantamango, MD, a post-doctoral research fellow with Adventist Health Study-2 at Loma Linda University. "While a majority of past research has focused on broad food groups, such as fruits and vegetables, in relation to colon cancer, our study focused on specific foods, as well as more narrowed food groups, in relation to colon polyps, a precursor to colon cancer. Our study confirms the results of past studies that have been done in different populations analyzing risks for colon cancer."
Colon cancer is the second leading cause of cancer death in the United States and the third most common cancer in both men and women, according to the American Cancer Society.
Results also show that consuming cooked green vegetables once a day or more, as compared to less than five times a week, was associated with a 24 percent reduction in the risk of rectal/colon polyps. Consuming dried fruit three times a week or more, versus less than once a week, was associated with a 26 percent reduced risk.
The protective effects of these foods could be due in part to their cancer-fighting agents, the study reported.
"Legumes, dried fruits, and brown rice all have a high content of fiber, known to dilute potential carcinogens," Dr. Tantamango says. "Additionally, cruciferous vegetables, such as broccoli, contain detoxifying compounds, which would improve their protective function."
Past studies examining the effect of meat intake and legumes on colon cancer have shown that people eating meat, associated with an increased risk of colon cancer, may receive some protection when they also consume legumes. Dr. Tantamango says this suggests that besides fiber content, there may be something else present in legumes that provides a protective effect.
Researchers analyzed data from 2,818 subjects who participated in Adventist Health Study-1 (administered from 1976-77) and who answered a follow-up survey 26 years later from Adventist Health Study-2. The first survey asked respondents to indicate how often, on average, they consumed specific foods. The follow-up survey asked respondents who had undergone colonoscopies to indicate physician-diagnosed colorectal polyps. During the 26-year follow-up, 441 cases of rectal/colon polyps were identified.
The study assessed several possible confounding factors, including a family history of colorectal cancer, education, physical activity level, alcohol intake, smoking, constipation, intake of sweets, pain medication, and multivitamins, as well as different food variables. The study then adjusted for those factors that were shown to distort the effect of the foods and food groups under study. About 25 foods and food groups in total were examined.
Dr. Tantamango says there is a need for future studies to examine foods shown to reduce the risk of colon polyps, since it is possible that interactions between various nutrients with anti-cancerous properties will be better able to explain these findings.