The greying of the population assures a continued prominence for osteoporosis and its consequences. The “story line” of vitamin D in relation to osteoporosis is fairly straightforward: As vitamin D levels decline to suboptimal levels (actual number of what constitutes “suboptimal” is still hotly debated), secondary hyperparathyroidism develops, resulting in accelerated bone loss. To date, clinical trials have not confirmed a fracture reduction benefit from vitamin D supplementation, and even the relationship between vitamin D status and bone mineral density (BMD) is plagued with inconsistencies. To further clarify the question of the relationship between vitamin D and BMD, Reid et al performed a meta-analysis of clinical trials that evaluated the effects of vitamin D on BMD.

 The clinical trial results (23 studies, n = 4082) were quite mixed, with some showing BMD benefit, some detriment, and some neutral. In essence, the net small benefit suggested by some trial data was of dubious clinical significance. These results should be distinguished from data on vitamin D in combination with calcium supplementation; since many trials provide vitamin D in combination with calcium (calcium does increase BMD), it has been sometimes misconstrued that each component of the vitamin D/calcium combo contributed to better BMD. The authors suggest that vitamin D would be best suited for persons with vitamin D insufficiency, rather than for all persons at risk for osteoporosis.