Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/30/2007
Publication Date: 11/1/2007
Citation: Finley, J.W., Burrell, J., Reeves, P.G. 2007. Pinto Bean Consumption Changes SCFA Profiles in Fecal Fermentations, Bacterial Populations of the Lower Bowel, and Lipid Profiles in Blood of Humans. Journal of Nutrition. 137:2391-2398. Interpretive Summary: Eating beans is known to improve serum cholesterol in humans, and it may reduce the risk of colon cancer by increasing the production of short chain fatty acids by bacterial fermentation in the colon. Our objectives were to determine whether eating cooked dry pinto beans would affect the fermentation products of colon bacteria, change the populations of various bacteria in the colon, and affect cholesterol and other lipids in serum of humans. Healthy men and women, or those with a tendency for cardiovascular disease, were fed ½ cup of cooked dried pinto beans for twelve weeks. The control groups were fed chicken soup that contained similar amounts of fat and calories as the beans. Eating beans significantly lowered total cholesterol by about 8% in the healthy people and 4% in those who had a tendency for cardiovascular disease. Those who ate beans maintained a higher bacterial production of propionic acid, which might be related to the lowering of cholesterol. However, significant changes in the populations of bacteria were not related to the formation of their fermentation products. We conclude overall that eating beans for as little as three months can decrease total serum lipids but does not change bacterial fermentation products or bacteria populations related to colon health.
Technical Abstract: Background: Beans improve serum lipids and may reduce the risk of colon cancer by increasing colonic short chain fatty acid (SCFAs) formation. Objective: We assessed whether pinto bean consumption affects 1) in vitro fecal bacterial fermentation and production of SCFAs, 2) colonic bacterial populations, and 3) serum lipids. Design: Adults grouped as pre-metabolic syndrome (pre-MetSyn, n=40) or Control (n=40) were randomly assigned to consume either a bean entrée (1/2 cup of dried, cooked pinto beans, or an isocaloric chicken soup entrée daily for 12 wk. Measurements included in vitro fecal fermentations of various resistant starch substrates, blood lipids, and fecal bacterial speciation. Results: Bean consumption increased propionate production (P<0.05) from fecal material fermented in vitro with bean flour, but did not affect total SCFA, acetic acid, propionic, or butyric acid. In the control volunteers only, bean consumption decreased production of both propionic and butyric acids (P<0.001). In all volunteers, bean consumption decreased fecal production of isovaleric (P<0.05) and isbutyric (P<0.01) acids by nearly 50%. Bean consumption did not affect most of the fecal bacterial populations tested, except for a reduction in Eubacterium limosum. Beans significantly lowered total cholesterol (TC; P<0.014) by about 8% in the Controls and 4% in the pre-MetSyn group. Bean consumption lowered HDL-cholesterol (P<0.05) and LDL-cholesterol (P<0.05) in both groups without affecting serum triglycerides, VLDL cholesterol, or glucose. Conclusion: Bean consumption for 3 months did not substantially change SCFA or bacterial populations related to colon health, but decreased serum lipids.