The effect of dried plum on serum levels of receptor activator of NF-kB ligand, osteoprotegerin and sclerostin in osteopenic postmenopausal women: a randomised controlled trial

Although several studies have confirmed the bone-protective properties of dried plum, its exact mechanisms of action remain unclear. Recent research has shown that osteocytes may control bone formation via the production of sclerostin and bone resorption via the receptor activator of NF-kB ligand (RANKL) and its inhibitor osteoprotegerin (OPG). To investigate the mechanism of action of dried plum in reversing bone loss, we measured serum levels of RANKL, OPG and sclerostin in osteopenic postmenopausal women (n 160). Participants were randomly assigned to the treatment group of either 100 g dried plum/d or 75 g dried apple/d (comparative control) for 1 year. All participants received 500 mg Ca plus 400 IU (10mg) vitamin D daily. Bone mineral densities (BMD) of the lumbar spine, forearm, hip and whole body were assessed at baseline and at the end of the study using dual-energy X-ray absorptiometry. Blood samples were collected at baseline and after 12 months to assess bone biomarkers. Dried plum significantly increased the BMD of the ulna and spine in comparison with the control group. In comparison with corresponding baseline values, dried plum increased the RANKL levels by only þ1·99 v. þ18·33 % and increased the OPG levels by þ4·87 v. 22·15 % in the control group. Serum sclerostin levels were reduced by 21·12 % in the dried plum group v. þ3·78 % in the control group. Although percentage changes did not reach statistical significance (P#0·05), these preliminary data may indicate that the positive effects of dried plum on bone are in part due to the suppression of RANKL production, the promotion of OPG and the inhibition of sclerostin.