Osteoporosis is characterized as a disease of low bone density and increased fragility, which results in more than 8.9 million fractures annually, approximately one fracture every three seconds. Although osteoporosis is mainly present in female populations, men over the age of 50 also experience gradual bone loss. Hence, 39% of all osteoporosis related fractures result in men. Dietary interventions have been shown to benefit bone health in postmenopausal women. However, the mechanisms of action are not completely understood. There is evidence that the polarization state of macrophages may influence bone anabolism, where M2 polarized macrophage have been shown to secrete osteogenic factors that promote bone anabolism.The purpose of this research was to investigate the effects of dried plum supplementation on modulating cytokines involved in macrophage polarization, osteoblast differentiation biomarkers, and functional outcomes of bone health in osteopenic men. Sixty men (Group A, n=24; Group B, n=23; Group C, n=13) between the ages of 55 and 80 with moderate bone loss (T-score between -0.1 and -2.5 SD below the mean) were included in this study. Group A, B, and C consumed 100g, 50g, or 0g of dried plums daily for six months, respectively. All three groups also consumed a multivitamin containing 450mg calcium and 800 IU vitamin D. Serum samples of 49 participants (Group A n=18, Group B n=18, and Group C n=13) were analyzed at baseline, three months, and six months for concentrations of interleukin-6 (IL-6), interleukin-4 (IL-4), bone morphogenetic protein-2 (BMP-2), receptor activator of nuclear factor kappa-Β ligand RANKL, and tumor necrosis factor alpha (TNF-α). DXA scans were performed to measure site specific bone mineral density and bone mineral content at baseline, three months, and six months. Our results indicate that after supplementation of dried plums for six months there was no significant differences for anthropometric or body composition measurements. Neither dried plum group had a protective effect on bone density, however, there was a time dependent decrease in left hip BMD at six months compared to three months (p <0.05) and radius BMD at three months compared to baseline (p <0.05). A significant time*treatment effect was detected for concentrations of TNF-α for both dried plum groups compared to control. There were no significant differences for any of the other serum biomarkers assessed. Furthermore, there were no significant correlations between baseline BMD values and baseline concentrations of blood biomarkers. The results of our study indicate that six months of dried plum supplementation in men with moderate bone loss does not have bone protective properties. Perhaps, the participants in our study did not have a sufficient degree of bone loss at baseline to experience benefits from dried plums. Furthermore, our study demonstrated that dried plums attenuate increases in TNF-α, which is a proinflammatory cytokine that is involved in M1 macrophage polarization. Future research should focus on a wider range of baseline BMD scores, and should assess other biomarkers associated with macrophage polarization states to fully understand the relationship between the immune system and bone.
