RESUMO
BACKGROUND: Vitamin D deficiency is related to increased cancer risk and deaths. However, whether vitamin D supplementation reduces cancer mortality remains unclear, and several randomized controlled trials yield inconsistent results. METHODS: Medline, Embase, and the Cochrane Central Register of Controlled Trials were searched from their inception until 28 June 2022, for randomized controlled trials investigating vitamin D supplementation. Pooled relative risks (RRs) and their 95% confidence intervals (CIs) were estimated. Trials with vitamin D supplementation combined with calcium supplementation versus placebo alone and recruiting participants with cancer at baseline were excluded in the present study. RESULTS: This study included 12 trials with a total of 72,669 participants. Vitamin D supplementation did not reduce overall cancer mortality (RR 0.96, 95% CI 0.80-1.16). However, vitamin D supplementation was associated with a reduction in lung cancer mortality (RR 0.63, 95% CI 0.45-0.90). CONCLUSIONS: Vitamin D supplementation could not reduce cancer mortality in this highly purified meta-analysis. Further RCTs that evaluate the association between vitamin D supplementation and total cancer mortality are still needed.
RESUMO
BACKGROUND: low vitamin D status has been associated with an increased incidence of cardiovascular events. However, whether vitamin D supplementation would reduce the incidence of cardiovascular events remains unclear. PURPOSE: To perform a systematic review and meta-analysis of the effect of vitamin D supplementation on the mortality and incidence of cardiovascular events. DATA SOURCES: We searched Medline, Embase, and the Cochrane Central Register of Controlled Trials from their inception until 3 May 2022. STUDY SELECTION: Two authors searched for randomized clinical trials that reported vitamin D supplementation's effect on cardiovascular events outcomes. DATA EXTRACTION: Two authors conducted independent data extraction. DATA SYNTHESIS: We identified 41,809 reports; after exclusions, 18 trials with a total of 70,278 participants were eligible for analysis. Vitamin D supplementation was not associated with the mortality of cardiovascular events (RR 0.96, 95% CI 0.88-1.06, I2 = 0%), the incidence of stroke (RR 1.05, 95% CI 0.92-1.20, I2 = 0%), myocardial infarction (RR 0.97, 95% CI 0.87-1.09, I2 = 0%), total cardiovascular events (RR 0.97, 95% CI 0.91-1.04, I2 = 27%), or cerebrovascular events (RR 1.01, 95% CI 0.87-1.18, I2 = 0%). LIMITATION: Cardiovascular events were the secondary outcome in most trials and thus, might be selectively reported. CONCLUSION: In this meta-analysis of randomized clinical trials, vitamin D supplementation was not associated with a lower risk of cardiovascular events than no supplementation. These findings do not support the routine use of vitamin D supplementation in general.