The Cancer Research
There are several ways in which legumes may act to prevent cancer.
A serving of legumes provide at least 20 percent of the recommended daily amount of folate and fiber. Dietary fiber can act in several ways to lower cancer risk, including helping with weight control. (Excess body fat increases the risk of eight cancers.) Gut bacteria feed on fiber, which produces compounds that may protect colon cells. And folate is essential for healthy DNA and maintaining control of cell growth.
Dry beans, split peas and other legumes also contain a variety of phytochemicals that scientists are studying for their anti-cancer effects.
Current Evidence: AICR/WCRF Expert Report and its Updates (CUP)
Dry beans and other legumes contain dietary fiber. After a systematic review of the global scientific literature, AICR/WCRF analyzed how these factors affect the risk of developing cancer. This comprehensive review concluded that there is strong – probable – evidence that:
- foods containing dietary fiber DECREASE the risk of colorectal cancer
Evidence categorized as "probable" means there is strong research showing a causal relationship to cancer – either decreasing or increasing the risk. The research must include quality human studies that meet specific criteria and biological explanations for the findings. A probable judgement is strong enough to justify recommendations.
”…Beans, rich in fiber and a variety of phytochemicals, can contribute to a diet that helps lower risk for cancer.”
- Karen Collins, MS, RD, CDN.
Open Areas of Investigation: Laboratory Research
In laboratory studies, flavonoids found in legumes have slowed the development of cancers during several stages of development. Current research suggests that protection may come as much from directly affecting cell growth as from antioxidant activity. Lab studies suggest many phytochemicals in legumes may decrease growth factors and chronic inflammation, risk factors for many cancers, and increase self-destruction of cancerous cells. Animal and human studies show that healthful bacteria in the colon use fiber (resistant starch) in legumes to produce substances that seem to protect colon cells.
Animal studies related to the whole legume have primarily focused on cancers of the breast and colon. Relatively few studies show decreased colon cancer in animals fed dry beans. Even fewer studies suggest a potential link between beans and lower risk of breast cancer.
Open Areas of Investigation: Human Studies
Human studies include case-control studies, which compare groups of people with and without cancer checking for a difference in legume consumption. It also includes cohort studies that follow people without cancer for several years and then look at how many dried beans participants generally consumed.
Several studies link higher consumption of legumes with lower risk of colon cancer or the benign adenomas (polyps) that are the beginning of most colon cancer. But overall, human studies focusing on legumes and cancer risk have resulted in inconsistent findings. One reason may be that few Americans eat dry beans as a regular part of their diet, making comparison between groups that eat high and low amounts of beans difficult. Early data links regular bean consumption with a possible reduced risk of prostate and breast cancers, but more research is needed.