Beans, butyrate, and colon cancer prevention

Beans fall under the category of legumes, dry fruits from a specific family of plants.  Beans and other legumes, like peas and lentils, are among the world's most perfect foods. They stabilize blood sugar and promote satiety. Even a small portion can help you feel full, but I recommend eating a full cup of beans each day.  They can be flavored and spiced in lots of interesting ways, and there is a huge variety of beans to choose from – chickpeas, black-eyed peas, black beans, lima beans, pinto beans, lentils, red kidney beans, cannellini beans and many more.

Beans are rich in fiber and resistant starch, which are essential to human health. Eating beans, peas, or lentils at least twice a week has been found to decrease colon cancer risk by a full 50 percent.  Only twice a week – imagine the amount of colon cancer protection one could achieve by eating beans every day! [i]  Several other studies on beans and lentils have found similar results – decreased risk of colorectal adenomas and cancers in those who consume these legumes regularly.[ii]  How do beans provide such significant protection against cancer?

Beans are rich in hundreds of phytonutrients, but are unique foods because of their very high levels of fiber and resistant starch, carbohydrates that are not broken down by digestive enzymes.  These carbohydrates pass into the large intestine, where they are fermented by bacteria.  Short chain fatty acids, such as butyrate, are products formed in the intestine from bacterial fermentation of these undigested carbohydrates.[iii]  High butyrate concentrations in the colon have protective effects against carcinogenesis, contributing to the protective effects observed in epidemiological studies of bean intake.

Diminished butyrate concentrations have been demonstrated in the colons of ulcerative colitis and colon cancer patients. In studies using colon cancer cells, butyrate halts cell growth and proliferation and induces programmed cell death.  Butyrate may exert these effects by affecting gene expression – it has been shown to alter the expression of certain genes that regulate the cell cycle and cell death. Butyrate also increases expression of detoxifying enzymes, decreases activation of enzymes that promote cancer progression, and prevents tumors from acquiring a blood supply in cell culture and animal studies. Butyrate has anti-inflammatory actions that may also contribute to cancer prevention – suppression of pro-inflammatory molecules and transcription factors. Preliminary evidence suggests that butyrate can also limit the DNA damage caused by oxidative stress. [iv],[v],[vi]

Epidemiological, cell culture, and animal studies all support the idea that eating beans regularly provides strong protection against colon cancer.  Human studies are now confirming these findings. A 2009 study on colorectal cancer patients found that resistant starch altered the expression of two key cell cycle regulator genes in tumors, and also had an anti-proliferative effect.  We know that beans are healthful foods that promote weight loss, prevent diabetes, and are protective against colon cancer.[vii] So make beans a regular part of your diet in soups, salads, dips, burgers, and other tasty recipes.

Dr. Fuhrman is a best-selling author and board certified family physician specializing in lifestyle and nutritional medicine.  For more recipes and more information on nutritional excellence, visit Dr. Fuhrman’s website.

[i] Singh, P.N., and G.E. Fraser. 1998. Dietary risk factors for colon cancer in a low-risk population. Am J Epidem. 148: 761-74.

Aune D, De Stefani E, Ronco A, et al. Legume intake and the risk of cancer: a multisite case-control study in Uruguay. Cancer Causes Control. 2009 Nov;20(9):1605-15.

[ii] Agurs-Collins T, Smoot D, Afful J, et al. Legume intake and reduced colorectal adenoma risk in African-Americans. J Natl Black Nurses Assoc. 2006 Dec;17(2):6-12.

Lanza E, Hartman TJ, Albert PS, et al. High dry bean intake and reduced risk of advanced colorectal adenoma recurrence among participants in the polyp prevention trial. J Nutr. 2006 Jul;136(7):1896-903.

[iii] O'Keefe SJ, Ou J, Aufreiter S, et al. Products of the colonic microbiota mediate the effects of diet on colon cancer risk. J Nutr. 2009 Nov;139(11):2044-8.

[iv] Hamer HM, Jonkers D, Venema K, et al. Review article: the role of butyrate on colonic function. Aliment Pharmacol Ther. 2008 Jan 15;27(2):104-19.

[v] Williams EA, Coxhead JM, Mathers JC. Anti-cancer effects of butyrate: use of micro-array technology to investigate mechanisms. Proc Nutr Soc. 2003 Feb;62(1):107-15.

[vi] Faris MA, Takruri HR, Shomaf MS, Bustani YK. Chemopreventive effect of raw and cooked lentils (Lens culinaris L) and soybeans (Glycine max) against azoxymethane-induced aberrant crypt foci. Nutr Res. 2009 May;29(5):355-62.

[vii] Dronamraju SS, Coxhead JM, et al. Cell kinetics and gene expression changes in colorectal cancer patients given resistant starch: a randomised controlled trial. Gut. 2009 Mar;58(3):413-20.