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 x 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. This trial was registered at clinicaltrials.gov as NCT02822378.