Prunes preserve hip bone mineral density in a 12-month randomized controlled trial in postmenopausal women: the Prune Study

Background: Dietary consumption of prunes has favorable impacts on bone health, but more research is necessary to improve upon study designs and refine our understandings. Objectives: We evaluated the effects of prunes (50 g or 100 g/d) on bone mineral density (BMD) in postmenopausal women during a 12-mo dietary intervention. Secondary outcomes include effects on bone biomarkers. Methods: The single-center, parallel-arm 12-mo randomized controlled trial tested the effects of 50 g and 100 g prunes compared with a control group on BMD (every 6 mo) and bone biomarkers in postmenopausal women. Results: In total, 235 women (age 62.1 ± 5.0 y) were randomly allocated into control (n = 78), 50-g prune (n = 79), or 100-g prune (n = 78) groups. Compliance was 90.2 ± 1.8% and 87.1 ± 2.1% in the 50-g and 100-g prune groups. Dropout was 22%; however, the dropout rate was 41% for the 100-g prune group (compared with other groups: 10%, control; 15%, 50 g prune; P < 0.001). A group × time interaction for total hip BMD was observed in control compared with 50-g prune groups (P < 0.05) but not in control compared with 100-g prune groups (P > 0.05). Total hip BMD decreased -1.1 ± 0.2% in the control group at 12 mo, whereas the 50-g prune group preserved BMD (-0.3 ± 0.2%) at 12 mo (P < 0.05). Although hip fracture risk (FRAX) worsened in the control group at 6 mo compared with baseline (10.3 ± 0.5% compared with 9.8 ± 0.5%, P < 0.05), FRAX score was maintained in the pooled (50 g + 100 g) prune groups. Conclusions: A 50-g daily dose of prunes can prevent loss of total hip BMD in postmenopausal women after 6 mo, which persisted for 12 mo. Given that there was high compliance and retention at the 50-g dosage over 12 mo, we propose that the 50-g dose represents a valuable nonpharmacologic treatment strategy that can be used to preserve hip BMD in postmenopausal women and possibly reduce hip fracture risk.