Osteoporosis has significant public health importance for both women and men, where 54% of the U.S. population age 50 and older have low bone mineral density (BMD). Chronic inflammation alters bone remodeling, which is one contributor to bone loss; therefore, foods rich in antioxidants, such as dried plums (Prunus domestica L.), are of great interest for preventing chronic inflammation. Previously, dietary intervention with dried plums has been shown to prevent orichidectomy-induced decreases in BMD, microstructure, and biomechanics in male rats; however, this has yet to be studied in a clinical setting in adult males. The purpose of this study was to document the effects of two doses of dried plums on biomarkers of inflammation and bone metabolism in men after three months of consumption. Thirty-five men 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. The men were randomized into one of three groups: 100g dried plums, 50g dried plums, or control group. All three groups also consumed a multivitamin containing 450mg calcium and 800 IU vitamin D (Shaklee Corporation) to provide baseline protection against bone loss. Serum samples from the baseline and three-month time points were analyzed for C-reactive protein (CRP), glutathione peroxidase (GPx), bone-specific alkaline phosphatase (BALP), osteoprotegerin (OPG), osteocalcin, sclerostin, receptor activator of nuclear factor beta ligand (RANKL), and tartrate-resistant acid phosphatase type 5b (TRAP-5b). DXA scans were used to assess BMD and BMC of the whole body, lumbar vertebrae, total hip, and forearm. DXA scans of the lumbar vertebrae alongside TBS iNnsight® software were used to generate trabecular bone score (TBS). After three months, consumption of 100g dried plums was associated with a significant decrease in BMD of the radius (P=0.013), and serum concentrations of osteocalcin (P<0.001). Consumption of 50g of dried plum was associated with significant decreases in systolic blood pressure, serum OPG (P=0.003), and serum osteocalcin concentrations (P=0.040), and an increase in the OPG:RANKL ratio (P=0.041). The control group also saw significant decreases in systolic blood pressure, OPG (P=0.004), RANKL (P=0.010), and osteocalcin (P=0.049). There was a significant group*time effect for changes in OPG (P=0.019) and the OPG:RANKL ratio (P=0.039). There were no significant differences in any other measures assessed. TBS was significantly negatively correlated with age (r= -0.23, P=0.013), and positively correlated with body weight (r=0.25, P=0.007). Decreases in osteocalcin indicate a decrease in bone turnover, and a higher OPG:RANKL ratio indicates a greater number of RANKL is bound to OPG, and not to osteoclasts, thus down-regulated osteoclast activity. Therefore, regular consumption of either 100g or 50g dried plum for three months may make some contributions to bone formation and bone turnover activity, and minimal contribution to decreasing inflammation and improving bone density and quality. Furthermore, TBS correlation results indicate that bone quality may be associated with both age and body weight. Three months of consumption may not be long enough to manifest changes in bone; therefore, future analysis of data after six months and one year of dried plum consumption in a larger number of men is warranted.
