Incorporation of whole or milled dry edible beans into a high-fat diet improves bone structure in obese mice

Authors: Cao, Jay; Gregoire, Brian; Bussan, Derek

Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/3/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: Obesity, a risk factor for several chronic diseases, such as cardiovascular disease, type 2 diabetes, and metabolic syndrome, is largely preventable by a healthy diet and exercise. Healthy dietary pattern plays an important role in obesity prevention. Dry edible bean (Phaseolus vulgaris L.) is considered a healthy diet component. The 2020 USDA Dietary Guidelines for Americans recommend weekly intake up to one and half cups (three servings) of dry edible beans as part of healthy U.S.-style dietary pattern. We investigated whether including dry edible beans to a high-fat diet influences body composition and ameliorates bone deterioration in an animal model. We also evaluated differences of the whole bean and milled bean flour on bone structure and related biomarkers in mice. We demonstrated that incorporating of dry edible beans into a high-fat diet improves but does not fully prevent the high-fat diet induced bone loss. Milled bean flour appears to have greater impact on bone related changes than whole bean. These findings suggest reducing adiposity and/or preventing obesity should be a preferred dietary strategy to improve bone health, although bean consumption benefits bone in obesity.

Technical Abstract: Objectives: The 2020 USDA Dietary Guidelines for Americans recommend weekly intake up to 1.5 cups of dry edible beans (pulses) as part of healthy U.S.-style dietary pattern. Pulses contain great amounts of antioxidant bioactive components and fiber that have beneficial effects on bone. This study investigated whether incorporation of dried pulses to a high-fat diet improves bone metabolism in obese mice. We hypothesized that addition of either whole or milled beans into a high-fat diet mitigates bone deterioration in obese mice. Methods: Male C57BL/6 mice at 4-week-old were randomly assigned to four treatment groups (n=22-24/group) and one of the following diets ad libitum for 12 weeks: a normal-fat (NF; 4.1 kcal/g and 16% energy as fat), a high-fat diet (HF; 4.9 kcal/g and 48% energy as fat), or a HF diet containing either whole beans (HFWB) or milled bean flour (HFMB) at 15% w/w. Diets containing beans were formulated to have similar total energy, protein, and fiber content as the HF diet without beans. Data were analyzed using one-way ANOVA followed by Tukey-Kramer post hoc contrasts. Results: Food intake by animals fed either the HF, HFWB, or HFMB was less than that by those fed the NF (P < 0.05), but total energy intake was similar (P > 0.05), due to the higher energy content of the three HF diets. Mice fed the HF, HFWB, or HFMB had greater body weight and fat mass than those fed the NF. Mice fed the HFWB or HFMB but not the HF had higher lean mass than those fed the NF. Mice fed the HF, HFWB, or HFMB had 23%, 14%, and 12% lower tibial bone volume/total volume (BV/TV, P < 0.05), respectively, than those on the NF. Mice fed the HF but not the HFWB or HFMB had lower BV/TV in 2nd lumbar vertebrae than those fed the NF. The pooled HF plus bean groups had higher BV/TV and Connectivity density and lower SMI in tibia than the HF alone (P < 0.05). Pooled HF with bean groups had greater body weight, fat mass, plasma concentrations of tartrate-resistant acid phosphatase, C-terminal telopeptide of type 1 collagen, blood glucose than the HF diet alone. Milled bean flour had greater impact on body weight, fat mass, tibial structural model index, circulating leptin and glucose than whole bean relative to the HF alone, indicating milled beans may enhance the utilization of certain nutrients. Conclusions: These data indicate that incorporation of dry edible beans into a high-fat diet mitigates but does not fully prevent bone deterioration in obese mice.