Viewpoint: Dried plum, an emerging functional food that may effectively improve bone health

Osteoporosis is a debilitating disorder that affects both female and male, albeit to a greater extent in women than men. As the demographic shift to a more aged population continues, a growing number of men and women will be afflicted with osteoporosis and a search for potential non-pharmacological alternative therapies for osteoporosis is of prime interest. Aside from existing drug therapies, certain lifestyle and nutritional factors are known to reduce the risk of osteoporosis. Among nutritional factors, recent observations suggest that dried plum, or prunes (Prunus domestica L.) is the most effective fruit in both preventing and reversing bone loss. Animal studies and a 3-month clinical trial conducted in our laboratories have shown that dried plum has positive effects on bone indices. The animal data indicate that dried plum not only protects against but more importantly reverses bone loss in two separate models of osteopenia. Our initial animal study indicated that dried plum prevented the ovariectomy-induced reduction in bone mineral density (BMD) of the femur and lumbar vertebra. In another study, to mimic established osteoporosis, rats were ovariectomized and allowed to lose bone before the initiation of treatment. Dried plum as low as 5% (w/w) restored BMD to the level of intact rats. More importantly, dried plum reversed the loss of trabecular architectural properties such as trabecular number and connectivity density, and trabecular separation. We have also shown the effectiveness of dried plum in reversal of bone loss due to skeletal unloading. Analysis of BMD and trabecular bone structure by microcomputed tomography (μCT) revealed that dried plum enhanced bone recovery during re-ambulation following skeletal unloading and had comparable effects to parathyroid hormone. In addition to the animal studies, our 3-month clinical trial indicated that the consumption of dried plum daily by postmenopausal women significantly increased serum markers of bone formation, total alkaline phosphatase, bone-specific alkaline phosphatase and insulin-like growth factor-I by 12, 6, and 17%, respectively. This review summarizes the findings of studies published to date which examine the beneficial effects of dried plum on bone in both female and male animal models of osteoporosis as well as the only published clinical study.