(P44-33-26) Effects of Prunes on Calcium Retention and Bone Parameters in Adult Gonadectomized Rats

Objectives: Prunes have demonstrated bone protective effects in both animal and human studies; however, the mechanisms remain unclear. This preclinical study investigated the acute and chronic effects of 15% prune intervention on calcium absorption and retention.

Methods: Eleven-week-old, ovariectomized (OVX) or orchidectomized (ORX), Sprague Dawley and rats (n=52) were assigned, within sex, to one of two dietary  groups: (1) Control (Con; n=13), polyphenol-free purified diet; or (2) Prune (15%; n=13), 15% (w/w) prune. Two 4-day net calcium balance studies were conducted during the initial and final phases of the 21-d intervention. At the beginning of the second balance period, rats received either oral or intravenous Ca-45 to estimate calcium absorption efficiency via femur uptake.  Calcium concentration in diet, fecal, and urine samples was measured by inductively coupled plasma optical emission spectrometry (ICP-OES). Femurs and lumbar vertebrae (L1-L5) were collected for assessment of bone physical properties.  Group differences were evaluated using Student’s t-test with significance set at P < 0.05.

Results: ORX-15% rats exhibited greater calcium retention (3.0 mg/d vs -30.1mg/d) and net calcium absorption (4.8 mg/d vs -26.3 mg/d) compared with ORX-Con during the acute intervention (P < 0.05); however, these differences were not sustained during chronic feeding, confirmed by lack of prune effect on calcium absorption efficiency. In OVX-15% rats, vertebrae (L1-L5) volume was greater (1.6 mL vs 1.2 mL), while vertebral density was lower (1.2 mL vs 1.3 mL) compared with OVX-Con (P < 0.05). A similar pattern was observed in ORX rats, with increased vertebral volume (L3) and reduced density (L1-L5) in prune-fed animals relative to controls.

Conclusions: Prune enhanced calcium absorption and retention during the acute phase of intervention; however, these effects attenuated with chronic feeding. These findings support prune as a potential dietary strategy to improve bone health, although sustained benefits may require an intermittent feeding approach.

Funding Sources: California Prune Board