Effects of vitamin D supplementation on nonskeletal outcomes
There has been no evidence to support the causal link between vitamin D supplementation and risk of nonskeletal diseases such as cardiovascular diseases (CVDs), type 2 diabetes (T2D) or malignancies, a new systematic review of meta-analyses shows.
Analysis of seven meta-analyses (21 randomized controlled trials [RCTs]) and three systematic reviews on vitamin D levels and CVD risk showed no harmful or beneficial effects of vitamin D on risks of CV events, myocardial infarction, CV death or stroke or cerebrovascular diseases.
Only two of nine meta-analyses (four RCTs each) and eight of 59 individual RCTs reported significant declines in systolic blood pressure (SBP) and no effect on diastolic blood pressure (DBP) following vitamin D supplementation. In contrast, one meta-analysis reported higher SBP in obese adults after vitamin D supplementation.
Eight systematic reviews investigated the effects of vitamin D on cancer risk, of which only five were formal meta-analyses. While the reviews included support no causal link between cancer and vitamin D, it should be noted that most RCTs were in samples without low 25OHD levels and have had short intervention duration, which may have affected the outcomes.
Of the four meta-analyses on vitamin D and depression, only one supported a significant beneficial link. However, the remaining three meta-analyses included more RCTs and the methods employed in each RCT showed a high degree of heterogeneity. A low vitamin D level at baseline was also not an inclusion criteria in most RCTs included.
RCTs, systematic reviews and meta-analyses investigating the effects of vitamin D supplementation on non-skeletal outcomes were searched from PubMed, the Cochrane Library and Embase. The qualities of the selected meta-analyses were mostly fair to good, according to the AMSTAR quality measurement tool.