Vitamin D and bone health: key involvement of physical activity

Abstract

In a recent substudy of the randomized, doubleblind, placebo-controlled ViDA trial that included a total of 452 community-dwelling older adults (placebo group: n = 224, mean age 68.6 years, 65% male; vitamin D group: n = 228, mean age 69.0 years, 62% male), Reid et al.[1] investigated effects of monthly high-dose (100 000 IU) vitamin D 3 supplementation for 2 years on areal bone mineral density (BMD) in the lumbar spine, total hip, femoral neck and total body. I agree with the authors that the study is highly valuable towards a trial-based definition of vitamin D deficiency regarding bone health in generally healthy older adults [1] and would also like to discuss their important findings from a different point of view to clarify the current confusion over the use of vitamin D and/or calcium supplements.High-dose vitamin D supplementation partially prevented an age-related decrease in areal BMD but did not result in an increase in areal BMD; mean baseline levels of circulating 25-hydroxyvitamin D in the placebo and vitamin D groups were 56 and 55 nmol L À1, respectively, and significant treatment effects were detected in the total hip and femoral neck (both less than 1%) but not the lumbar spine or total body [1]. This is consistent with a recent meta-analysis of a total of 33 randomized clinical trials including more than 50 000 community-dwelling men and women older than 50 years that investigated the effects of calcium, vitamin D or calcium plus vitamin D supplements versus a placebo or no treatment on fracture risk [2]. The meta-analysis showed no significant associations between the use of these supplements and the incidence of hip fracture as well as nonvertebral, vertebral or total fractures, even in subgroups with lower than 50 nmol L À1 of serum 25-hydroxyvitamin D levels at baseline, dietary intake with lower than 900 mg day À1 of calcium or supplementation with higher than 800 IU day À1 of vitamin D and higher than 1000 mg day À1 of calcium. Consequently, in generally healthy older adults, there seems to be little causal relationship of vitamin D status with musculoskeletal outcomes such as areal BMD in contrast to the results from many observational studies. Areal BMD in the hip was, for example, more than 10% lower in older women with serum 25-hydroxyvitamin D levels below 30 nmol L À1 versus above 80 nmol L À1 during the sunny summer season in a population-based cohort [3], whereas high-dose vitamin D supplementation only prevented the age-related decrease in areal BMD in the hip by around 2% in older adults with less than 30 nmol L À1 of serum 25-hydroxyvitamin D levels at baseline although its levels during the supplementation were over 80 nmol L À1 [1]. Accumulating experimental evidence indicates that vitamin D affects the skeleton mainly by controlling calcium absorption in the intestine, which is unlikely to support further cumulative effects with vitamin D supplementation longer than two years because a meta-analysis suggests that calcium supplements or increasing calcium intake can have smal...

Bariatric Surgery, Physical Activity, and Fracture Risk

“…Indeed, these findings are compatible with results from a prospective study including obese premenopausal women with either type of bariatric surgery, sleeve gastrectomy or Roux‐en‐Y gastric bypass, that the latter type caused significantly larger bone loss in the femoral neck, but not the lumbar spine, compared with the former type as expected, whereas both types markedly and similarly reduced calcium absorption in the gut . Here, it should be paid attention that physical activity can also provide an insight into such limited effects of calcium/vitamin D malabsorption after bariatric surgery. Nevertheless, adequate intakes of calcium/vitamin D as well as protein have been generally recommended for patients who have had bariatric surgery, and randomized controlled trials are expected to identify the optimal doses of calcium/vitamin D supplementation in the near future.…”

Towards a Consensus on Vitamin D Supplementation and Bone Health

“…Consequently, the possibility of a causal positive association between serum 25(OH)D levels and aBMD would be almost ruled out by these two key analyses to assess causality, though the indirect effects of high‐dose vitamin D supplements in RCTs could be detected in the hip or tibia . Accordingly, the positive linear correlation between serum 25(OH)D levels at 12 months and change in aBMD in the lumbar spine can be interpreted as a result of the involvement of individual life and health status including physical activity outdoors because the wide variability in serum 25(OH)D levels after supplementation with vitamin D suggests that serum 25(OH)D levels at 12 months resulted not only from vitamin D supplements, but also from other factors such as vitamin D synthesis in the skin following sunlight exposure.…”

“…serum 25(OH)D levels at 12 months and change in aBMD in the lumbar spine (5) can be interpreted as a result of the involvement of individual life and health status including physical activity outdoors (12) because the wide variability in serum 25(OH)D levels after supplementation with vitamin D (5) suggests that serum 25(OH)D levels at 12 months resulted not only from vitamin D supplements, but also from other factors such as vitamin D synthesis in the skin following sunlight exposure.…”