News & Emerging Research about Beans and Health
Pinto bean consumption changes SCFA profiles in fecal fermentations, bacterial populations of the lower bowel, and lipid profiles in blood of humans
Finley JW, Burrell JB, and Reeves PG. -2007. Journal of Nutrition 137: 2391-2398
Accumulating data suggest that beans lower serum lipids in human subjects and lower the risk of colon cancer via greater short-chain fatty acid (SCFA) production. This USDA study examined the hypothesis that pinto bean consumption affects SCFA production, colonic bacterial populations, and serum lipids. The study used 40 adults with premetabolic syndrome (pre-MetSyn; metabolic syndrome is a cluster of metabolic conditions that signal risks for coronary heart disease and type 2 diabetes) and 40 controls. Subjects were randomly assigned to consume either a bean entrée [1/2 cup (130 g) of dried, cooked pinto beans] or a chicken soup entrée (equal calories to bean meal) daily for 12 weeks. Relative to baseline, propionate SCFA production from fecal material fermented in vitro with bean flour was greater in adults consuming beans relative to the soup group. The most robust effects were seen with bean consumption and lipid profiles. Specifically, beans lowered serum total cholesterol by approximately 8% in the controls and 4% in the pre-MetSyn group. Bean consumption lowered serum HDL-cholesterol and LDL-cholesterol in both groups without affecting serum triglycerides, VLDL cholesterol, or glucose. This study indicates that bean consumption can favorably affect lipid profiles associated with cardiovascular disease, however, the data do not indicate clear health benefits associated with colon cancer risk.
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The researchers demonstrated that daily consumption of pinto beans can have several cholesterol-lowering benefits (i.e., total and LDL-cholesterol) in both healthy subjects and in those preconditioned for metabolic syndrome.
In fact, the authors stated that, “the treatment differences were of such magnitude that significance was found to be both statistical and physiological.
This study adds to a growing and convincing body of evidence that adding dry beans to the diet in quantities of at least 100 g/d changes lipid profiles in a manner associated with decreased risk of cardiovascular disease.”
Nonetheless, the investigators were not able to provide a rationale as to why bean consumption lowered HDL cholesterol (i.e., higher HDL-cholesterol levels lower the risk of heart disease) while no changes were observed for triglycerides. As such, future research is necessary to unravel such unexpected results.
Diet and survival after prostate cancer diagnosis
Berkow S, Barnard ND, Saxe GA, et al.– 2008. Nutrition Reviews 65: 391-403
This review considered eight observational and 17 intervention studies that examined the relationship of plant-based diets to prostate cancer. Overall, vegetable components that reduced the risk of prostate cancer included fiber, specific nutrients and antioxidants. One potential mechanism suggested that plant components function by way of altering levels of hormones that favor tumor growth. The researchers concluded that “these studies suggest that plant-based diets that are high in fiber and phytonutrients and low in fat and saturated fat, favorably influence health outcomes for prostate cancer patients.” In addition, individuals who adopt a plant-based diet following cancer onset may experience a slower rate of progression relative to those not consuming plants.
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Beans and other legumes fit the profile of being a plant food rich in fiber and phytonutrients and low in total and saturated fat.
Since several scientific studies are now available linking plant food consumption and reduced cancer risks, it is imperative to conduct trials looking at individual plant foods and consumption levels necessary to observe health benefits.
Imagine the day when you can say, “Eating one can of baked beans per day, as part of a diet low in total and saturated fat, can reduce your chances of prostate cancer by 50%”… everything starts with a dream!
Association between dietary glycemic index and age related macular degeneration in nondiabetic participants in the Age-Related Eye Disease Study
Chiu C-J, Milton RC, Gensler G et al.– 2007. American Journal of Clinical Nutrition 8: 180-188
Researchers at the USDA assessed whether the dietary glycemic index is associated with the risk and severity of age-related macular degeneration (AMD), a condition leading to blindness, in an elderly population. Dietary data was obtained from nearly 4,100 subjects (aged 55- to 80-years-old). Individuals in the fourth and fifth quintiles had greater risk of large drusen, atrophy and neovascularization (i.e., attributes of AMD). Researchers also observed that AMD severity increased with a greater dietary glycemic index.
The researchers also stated, “that 20 percent of the cases of advanced AMD might have been prevented if those individuals had consumed a diet with a glycemic index below the average for their age and gender.” Thus, a reduction in dietary glycemic index may provide a non-invasive method of decreasing the risk of AMD.
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There continues to be a growing body of evidence in support for consuming a low-glycemic index diet. This study provides data to show that a high-glycemic index diet can be detrimental to eye health.
Once again, a great opportunity exists for the bean manufacturers and growers to scream out the benefits of bean consumption…not just colon health anymore!
In order to get there though, we need controlled clinical studies that look at the specific effects of chronic bean consumption and age-related macular degeneration.