Vitamin D deficiency is associated with increased risk of all-cause and cardiovascular mortality (Arch Intern Med 2008 Jun 23;168(12):1340). Studies have suggested that vitamin D supplementation may reduce cancer and cardiovascular disease, but evidence for the effects of supplementation on mortality has been inconsistent. A recent Cochrane review evaluated different forms of vitamin D supplements and found that different forms have different effects on mortality. The review included 50 randomized trials comparing any vitamin D supplement to placebo or no intervention in 94,148 patients. Most of the participants were women > 70 years old. The median treatment duration was 2 years.
In an analysis of 32 trials with 74,789 patients, vitamin D3 (cholecalciferol) significantly decreased all-cause mortality (relative risk [RR] 0.94, 95%CI 0.91-0.98), with an NNT of 161, assuming 10% mortality in controls (level 1 [likely reliable] evidence). Subgroup analyses revealed that this risk reduction was driven primarily by patients with insufficient levels of vitamin D.
There were no significant differences in mortality associated with other forms of vitamin D, including vitamin D2 (ergocalciferol) (12 trials), alfacalcidol (4 trials), or calcitriol (3 trials) (level 2 [mid-level] evidence). Alfacalcidol and calcitriol, both active forms of vitamin D, were associated with increased risk of hypercalcemia. Vitamin D3 combined with calcium supplementation was associated with increased risk of renal calcium stone disease (Cochrane Database Syst Rev 2011 Jul 6;(7):CD007470).
For more information, see the Vitamin D deficiency in adults and Vitamin D intake and supplementation topics in DynaMed.