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

Objectives: Pulses, a healthy diet component, contain many bone beneficial components. This study investigated whether incorporation of dried pulses to a high-fat diet improves bone metabolism in obese mice.

Methods: Male C57BL/6 mice at 4-week-old were randomly assigned to four diet groups (n=22-24/group) 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 had similar total energy, protein, and fiber content as the HF diet without beans. Bone structure and related biomarkers were measured. Data were analyzed using one-way ANOVA followed by Tukey-Kramer post hoc contrasts.

Results: Mice fed the HFWB or HFMB but not the HF had higher lean mass than those fed the NF (P < 0.05, 9.1 and 8.7%, for HFWB and HFMB, respectively). 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 9.2% lower BV/TV in 2nd lumbar vertebrae than those fed the NF (P < 0.05). Pooled HF with bean groups had 18, 14, 27, 17, and 15% 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, respectively (P < 0.05). 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.

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.