Incorporation of Whole or Milled Dry Edible Beans into a High-Fat Diet Improves Bone Structure in Obese Mice.

Background: Pulses, a healthy diet component, have many bone-beneficial nutrients.

Objectives: 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-wk-old were randomly assigned to 4 diet groups (n = 22-24/group) for 12 wk: a normal-fat (NF; 4.1 kcal/g and 16% energy as fat), a HF (4.9 kcal/g and 48% energy as fat), or a HF containing either whole beans (HFWB) or milled bean flour (HFMB) at 15% wt/wt. Diets containing beans had similar total energy, protein, and fiber content as the HF without beans. Bone structure and related biomarkers were measured. Data were analyzed using a 1-way analysis of variance 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 (P < 0.05), respectively, than those on the NF. Mice fed the HF but not the HFWB or HFMB had 9.2% lower bone volume/total volume in the second 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 alone, respectively (P < 0.05). Milled bean flour had a 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 the incorporation of dry edible beans into a HF mitigates but does not fully prevent bone deterioration in obese mice.