Abstract
The dietary fiber gap that is present in many countries co-exists with a low intake of grain legumes (pulses) that have 2–3 times more dietary fiber than cereal grains that are commonly recommended to increase fiber intake. Given the relationships among dietary fiber, gut health and chronic disease risk, a study was undertaken in a preclinical mouse model for obesity to examine how commonly consumed pulses, i.e., chickpea, common bean, dry pea and lentil, would impact gut microbes, intestinal function, and adiposity. Pulses were fed to C57BL/6 mice at similar levels of protein and fiber. Bacterial count in the cecum was elevated 3-fold by pulse consumption. At the phylum level, a 2.2- to 5-fold increase in Bacteriodetes relative to Firmicutes was observed. For Akkermansia muciniphila, a health-beneficial bacterium, differential effects were detected among pulses ranging from no effect to a 49-fold increase. Significant differences among pulses in biomarkers of intestinal function were not observed. Pulses reduced accumulation of lipid in adipose tissue with a greater reduction in the subcutaneous versus visceral depots. Metabolomics analysis indicated that 108 metabolites were highly different among pulse types, and several compounds are hypothesized to influence the microbiome. These results support recent recommendations to increase consumption of pulse-based foods for improved health, although all pulses were not equal in their effects.
Highlights
In many regions of the world, grain legumes, referred to as pulses, are neglected staple foods that have the potential to directly impact food insecurity while helping individuals achieve healthy and balanced diets and to accelerate progress towards the Sustainable Development Goals of the WHO/FAO [1,2,3,4,5]
Key aspects of the dietary approach were: (1) the inclusion of a low-fat, negative control group, which varied markedly in composition from the high-fat control but that is a recognized control in the B6 DIO model in that it does not induce dysbiosis and has lower obesogenic activity [44], (2) the use of a single common bean market class as a “gold standard” against which to compare the activity of other pulses since we have reported that this common bean market class has anti-cancer and anti-obesogenic activity and that it induces favorable changes in gut microbial populations in this model system [41,45,46], and
This study has several limitations. They include (1) the inability to fully match chemical composition across dietary formulations when a whole food approach is used; we argue that this approach is essential for understanding how the consumer may benefit from pulse crop consumption; (2) pulses were cooked and immediately freeze dried; the potential impact of this approach on qualitative changes in carbohydrate constituents is unknown, but this approach is being used to make commercially available pulse powders that are being used as ingredients in the design of new food products; and (3) content of specific bacterial populations was determined by qPCR; while not as much information is obtained about overall microbial ecology as attained via high-throughput techniques, qPCR is a rapid, specific, and cost effect method [50]
Summary
In many regions of the world, grain legumes, referred to as pulses, are neglected staple foods that have the potential to directly impact food insecurity while helping individuals achieve healthy and balanced diets and to accelerate progress towards the Sustainable Development Goals of the WHO/FAO [1,2,3,4,5]. The majority of individuals in developed countries such as the United States fail to meet the recommended level of intake for dietary fiber and the magnitude of the gap is large, an approximately 50–70% shortfall [6]. This gap has been resistant to change, despite decades of public health interventions and development of fiber enriched food products. We have advocated more focus on pulse crops to close the dietary fiber gap, but to extend intake above recommended levels to those that have been reported to significantly reduced chronic disease mortality [14]. To achieve such intakes, i.e., 50–80 g total dietary fiber per day, we argue that a better understanding of the effects of high fiber foods such as pulses is needed
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