Role of Monthly High-Dose Vitamin D Supplementation in Cancer Prevention—In Reply

In Reply Peiris and colleagues commented on the null effect of vitamin D supplementation on incident cancer in the ViDA study, which is based primarily on possible differential effects on disease risk between daily vs monthly doses of vitamin D supplementation. In our article, we acknowledged that monthly dosing may be less effective than daily dosing for preventing cancer, and we agree that if this finding is true, increased variability in vitamin D levels associated with monthly dosing would be a possible mechanism. For example, daily or weekly dosing of vitamin D is more effective than bolus dosing (ie, monthly) in preventing acute respiratory infections, particularly in people with vitamin D deficiency. However, the recent null findings for incident cancer reported in the VITAL study, in which a daily dose of vitamin D was administered, suggest that the frequency of dosing is not important for cancer prevention.

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