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. Therefore, 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. Several animal studies, a 3-month and a one-year long clinical trials conducted in our laboratories have shown that dried plum has positive effects on bone indices and bone mineral density (BMD).
The animal data indicate that dried plum not only prevents but more importantly reverses bone loss in two separate models of osteopenia. Our initial animal study indicated that dried plum prevented the ovariectomy-induced BMD reduction of the femur and lumbar vertebra. In another study rats were ovariectomized and allowed to lose bone before the initiation of treatment to mimic established osteoporosis. Dried plum as low as 5% (w/w) gram per kilogram diet restored BMD to the level of intact rats. Dried plum also reversed the loss of trabecular architectural properties such as trabecular number, connectivity density, and trabecular separation. We have also shown the effectiveness of dried plum in reversal of bone loss due to skeletal unloading. Microcomputed tomography (µCT) analyses revealed that dried plum enhances bone recovery during reambulation following skeletal unloading and has comparable effects to parathyroid hormone. In addition to the animal studies, our 3-month clinical trial indicated that the consumption of dried plum daily significantly modulated serum markers of bone turnover in postmenopausal women.
To confirm the findings of the animal studies and the 3- month clinical trial, we conducted a relatively long-term randomized comparative-controlled clinical trial. The principal objective of this study was to examine the extent to which dried plum reverses bone loss in osteopenic postmenopausal women. We recruited 236 women, 1 to 10 years postmenopausal, not on hormone replacement therapy or any other prescribed medication known to influence bone metabolism. One hundred and sixty qualified participants were randomly assigned to one of two treatment groups: dried plum (100 g/d) or dried apple (comparative control) for one year. All study participants received 500 mg elemental calcium plus 400 IU vitamin D daily. Bone mineral density of lumbar spine, forearm, hip, and whole body were assessed at baseline and the end of the study using dual-energy x-ray absorptiometry. Blood and 24-hr urine samples were collected at baseline, 3-, 6-, and 12-month to assess bone biomarkers and bone metabolism measurements. Physical activity recall and one-week food frequency questionnaire were obtained at baseline, 3-, 6-, and 12-month to examine physical activity and dietary confounders as potential covariates. Dried plum significantly increased BMD of ulna and spine in comparison to the dried apple group. In comparison with corresponding baseline values, only dried plum significantly decreased serum levels of bone turnover markers including bone-specific alkaline phosphatase and tartrate resistant acid phosphatase-5b.
