A growing body of evidence from large population studies and comprehensive reviews indicates legumes may have a protective effect against bowel, breast, lung and prostate cancers.
Colorectal Cancer
In 2011, the World Cancer Research Fund concluded the evidence for a protective effect of high fibre foods such as legumes against colorectal cancer is convincing. This is in-line with the findings of a meta-analysis of observational studies found that eating legumes is associated with a reduced risk of bowel cancer. An analysis of the Nurses’ Health Study, found those who consumed four or more servings of legumes a week had a lower incidence of colorectal adenomas than women who reported consuming one serving or less.
Breast Cancer and Soy
Population studies indicate soy consumption has a role in both preventing breast cancer and reducing risk of re-occurrence in breast cancer survivors. Two meta-analyses have concluded there is a 14-25% reduced risk of breast cancer with high soy food intakes. The potential influence of soy isoflavones on breast cancer prognosis as well as their interaction with the hormonal therapy tamoxifen have led to concern about soy food consumption among breast cancer patients. These concerns have stemmed from the results of in-vitro and animal studies, but the relevance of these results in women consuming soy foods is not established. Importantly, recent evidence indicates that there is no increased risk of breast cancer recurrence or increased mortality with increased soy intake in breast cancer patients.
Suggested Mechanisms
The mechanisms of cancer protection are not clearly understood. Legumes contain several phenolic compounds, in addition to glutathione, soluble proteins and tocopherols which are considered to be natural antioxidants and may provide some cancer protective effects.
Legumes are also significant sources of resistant starches, which are fermented by colonic bacteria to short chain fatty acids, thus improving colonic health.
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