Baked bean consumption reduces serum cholesterol in hypercholesterolemic adults

Abstract

Baked bean consumption has been linked to reductions in total cholesterol (TC), and low-density lipoprotein cholesterol (LDL-C) in previous research with hypercholesterolemic adult men in controlled settings. The objective of the current research was to determine if daily intake of half a cup of vegetarian baked beans would reduce risk factors for coronary heart disease and type 2 diabetes in free-living hypercholesterolemic men and women over an 8-week period. The study was a randomized, crossover, 2 × 2 block design. Participants received each treatment for 8 weeks with a minimal 14-day washout in between. Fasting blood samples collected at the beginning and end of the study were analyzed for TC, LDL-C, high-density lipoprotein cholesterol, triacylglycerols (TAG), high-sensitivity C-reactive protein, insulin, glucose, homeostasis model assessment, and hemoglobin A_1c. A significant absolute decrease in TC concentrations after 8 weeks (P = .01) was observed with the vegetarian baked bean treatment in contrast to the control. Mean percentage change of serum TC for baked beans was −5.6% ± 1.5% SEM in contrast to 0.5% ± 1.8% SEM for the control (P = .01). Mean percentage change of serum LDL-C was −5.4% ± 2.3% SEM and 1.0% ± 2.7% SEM (P = .08, nonsignificant), respectively. No significant differences were found with the other blood concentrations. These findings indicate that vegetarian baked bean consumption can reduce serum TC in hypercholesterolemic adults.

Introduction

The health benefits of beans or legume consumption have received increasing attention from researchers and the media. Similar to other vegetables and fruits, legumes are an excellent source of many essential nutrients, including vitamins, minerals, fiber, phytochemicals, and antioxidants, as well as being associated with health-promoting benefits, such as lowering risk for chronic diseases including coronary heart disease (CHD). The Dietary Guidelines for Americans recommends including half a cup (130 g) in the diet several times a week for good health. Total recommendations per week are 3 1/2 cups [1].

Large-scale epidemiological studies have observed that CHD risk is lower among adults who frequently consume legumes. Results from the National Health and Nutrition Examination Survey Epidemiologic Follow-up Study indicate that men and women who reported consuming legumes 4 or more times per week had a 22% reduction in CHD risk, compared with those who consumed legumes less than once a week. Higher legume intakes were associated with lower body mass index (BMI), blood pressure, serum total cholesterol (TC), and a lower incidence of diabetes mellitus, compared with lower legume intakes [2]. A recent Costa Rican study observed that myocardial infarction (MI) survivors and their matched controls had a 38% lower risk of MI if they reported consuming at least 1/3 cup of cooked beans per day. Consuming amounts greater than this amount provided the same risk reduction but did not provide additional protection against MI [3]. The health benefits from beans appear to be multidimensional. In a 5-country longitudinal study of food habits among the elderly, legume consumption was the best predictor of survival. Risk of death was reduced by 8% for each daily 20-g intake of legumes [4].

Per capita consumption of navy beans at 1.3 lb ranks second only to pinto beans at 3.6 lb in the United States [5]. Most canned baked beans are made from navy beans [6]. Although 71% of pinto beans are eaten at places such as restaurants, 86% of navy beans are consumed in the home. US populations in the South and Midwest use 62% of the navy beans marketed in the United States [6]. Baked beans are also popular in Britain, with a per-capita consumption of 4 times that in the United States. Recent British national survey data indicate that young adults 19 to 24 years of age have shown an increase in baked bean consumption since the mid 1980s [7]. Thus, although baked beans are a popular food, the market share could be increased.

Several clinical trials have investigated the effects of baked beans on serum lipoproteins. Positive effects on CHD biomarkers have been reported. However, variations in previous study designs have made it difficult to compare studies to each other or to consistently replicate results. Some of the distinctions between trials include participant selection criteria, the amount of beans consumed, study period length, and types of outcomes measured [8]. Most studies have only included hypercholesterolemic men, and few have been with free-living populations.

Anderson et al [9] conducted some of the classic work in this area during the 1980s. They demonstrated that consumption of 275 g (∼1 cup) of navy beans for 3 weeks decreased serum cholesterol concentrations by 19% and low-density lipoprotein cholesterol (LDL-C) by 24% in hypercholesterolemic men. A second trial showed reductions of 23% in serum TC and LDL-C under metabolic ward conditions with a similar bean diet [10]. During a 2-week intervention, Shutler et al [11] also found that baked beans significantly reduced mean serum TC by 12% (P < .02) and mean serum high-density lipoprotein cholesterol (HDL-C) by 15% (P<.001). No changes in serum triacylglyerols (TAG) were observed, and LDL-C was not reported in this study. In a third trial, Anderson et al [12] observed the lipid responses of 24 hypercholesterolemic men fed baked beans in a metabolic ward clinical feeding trial after 3 weeks but using 3 diets that contained canned beans in tomato sauce at different dosages. Diets A and B contained 227 g of baked beans, and diet C contained 182 g. Diet A was consumed as a single dose, whereas diets B and C were consumed as divided doses. Changes in individual serum TC, LDL-C, and TAG values were combined for all 3 diets consumed and reported as mean percentage changes of −10.4% (P < .001), −8.4% (P < .005), and −10.8% (P < .05), respectively. The mean percentage change in HDL-C was −6.9% (P < .05). In contrast to these positive findings, Cobiac et al [13] fed equal amounts of baked beans and spaghetti in tomato sauce (440g) for 4 weeks each to 20 hypercholesterolemic men. Compared with baseline values, mean serum TC, LDL-C, and HDL-C, as well as serum TAG values, were not different after consuming the baked beans. The aim of the current study was to determine if eating half a cup of vegetarian baked beans for 8 weeks would result in improved biochemical markers of CHD in adults with hypercholesterolemia in a free-living setting.