Discussion
bone loss
OXIDATIVE STRESS, BONE LOSS
Freeze-dried BB powder at lower to moderate doses, but not higher doses, increased bone calcium balance in both OVX rats and healthy postmenopausal women. The rat study informed the doses chosen in the clinical study. In postmenopausal women, the effective doses were 17.5 g/d (best) and 35 g/d. The low dose BB improved bone balance by 6%, the equivalent of 41 g of total body calcium. In addition, a bone resorption marker RANKL was significantly reduced by the medium dose of BB powder. Bone formation marker P1NP was also reduced, suggesting a reduction in bone turnover overall, although it did not predict the urinary The lack of linear dose-response relationship is consistent with a report in OVX rats that a 100-d treatment with 5% (w/w semipurified diet) powdered freeze-dried blackberry, another polyphenol-rich fruit with similar phenolic content as BB, resulted in modest protection of tibial and femoral BMD, but no effect was seen with the higher dose of 10% [There are several possible mechanisms by which the hormetic effect could be mediated, including cellular redox status, bone osteoblast, and osteoclast activities, and changes in gut microbial composition. The high levels of polyphenols in BB are thought to be the bioactive components that might act as antioxidants, reducing oxidative stress and, therefore, preventing bone loss. Sato et al. [