Grain Legume Consumption Inhibits Colorectal Tumorigenesis: A Meta-Analysis of Human and Animal Studies

Abstract

Grain legume consumption has been linked in meta-analysis studies to decreased risk of metabolic syndrome, obesity, and cardiovascular diseases; however, the evidence for a chemo-protective effect of grain legume consumption against colorectal tumorigenesis has been considered inconclusive. We conducted a meta-analysis of human and animal studies to evaluate the effect of grain legume consumption on colorectal cancer (CRC) and its precursors. Twelve case-control studies (42,473 controls and 12,408 cases) and 11 prospective cohorts (1,533,527 participants including 12,274 cases) were included in the meta-analysis; the pooled risk ratio (95% confidence interval) for the highest versus the lowest legume intake group based on a random effects model was 0.72 (0.60-0.89) for incident adenoma, 0.91 (0.84-0.99) for prevalent adenoma, and 0.82 (0.74-0.91) for CRC. Fourteen animal studies (355 animals on grain legume diets and 253 animals on control diets) were included in the meta-analysis and showed in all but one study a chemo-preventive effect against colorectal tumorigenesis. Grain legumes contain various compounds (e.g., resistant starch, soluble fiber, insoluble fiber, phytosterols, saponins, phytates, flavonoids, proanthocyanidins, and phenolic acids) that have been shown to inhibit colorectal tumorigenesis in animal studies at concentrations that are relevant for human diets. Grain legume consumption alters several molecular pathways (e.g., p53, mTOR, NF-kB, Akt, and AMPK) that are critical for tumor induction, promotion, and progression. Based on our meta-analysis, daily grain legume consumption confers chemo-preventive effects against CRC.

Legume Consumption Patterns in US Adults: National Health and Nutrition Examination Survey (NHANES) 2011–2014 and Beans, Lentils, Peas (BLP) 2017 Survey

“…3 Each day means consumption on day 1 and 2 in NHANES and daily consumption in BLP. 4 Over 2 days means consumption on day 1 or 2 in NHANES and at least 3-4 days/week consumption in BLP.…”

“…To compare legume consumers by consumption level, we switched from any to mature legume consumption level, as dietary recommendations only exist for the latter. To identify characteristics that differentiate between mature-legume consumers that consume low amounts, those that consume amounts sufficient to fulfill dietary recommendations (37.5 g/day is the current dietary recommendations for cooked mature legume intake for non-vegetarians [6]), and those that consumed amounts needed to alter nutrient profile and show disease prevention benefits (87.5 g/day is amount needed to alter nutrient profile [5] and show disease prevention benefits [4,[7][8][9][10]), we compared marginal consumers (0.1-37.5 g cooked mature legumes/day), recommended consumers (37.5-87.49 g/day), and beneficial amount consumers (≥87.5 g/day), respectively. The NHANES analyses used weights designed to account for the unequal selection probabilities, adjustments to independent population controls, and nonresponse.…”

“…Approximately a quarter of mature-legume consumers, or 15% of the total population, ate mature legumes at levels required to achieve nutritional and, thereby, disease prevention benefits, as supported by multiple population studies and meta-analyses, including ours [4,[7][8][9][10]. We defined them as beneficial amounts mature-legume consumers.…”

“…Legumes are an important part of a daily diet because of their nutritional and health benefits [3]. They are a good dietary source of protein, fiber and folate, are very low in saturated fatty acids, cholesterol, and sodium, and contain many non-nutritive bioactive components [4]. Consuming 0.5 cup/day (87.5 g) of mature legumes increased fiber, protein, folate, zinc, iron, and magnesium intake and decreased saturated and total fat intake in US adults according to the nation-wide, cross-sectional National Health and Nutrition Examination Surveys (NHANES) 1999-2002 [5].…”

“…Based on their nutritional benefits, the current Dietary Guidelines for US Americans consider mature legumes as a food group with a weekly recommendation of 1.5 cups (equivalent to 37.5 g cooked mature legumes/day) for non-vegetarians and 3 cups (equivalent to 75 g cooked mature legumes/day) for vegetarians [6]. In addition to their nutritional benefits, daily mature legume consumption may have disease prevention benefits, specifically, preventing or managing obesity, metabolic syndrome, cardiovascular diseases, and colorectal cancer, as concluded by several meta-analyses [4,[7][8][9][10]. In NHANES 1999-2002, dry bean consumption was associated with low body weight, decreased systolic blood pressure, and a smaller waist circumference in US adults [11].…”