Vitamin D Supplementation and Antibiotic Use in Older Australian Adults: An Analysis of Data From the D-Health Trial

Abstract Background Vitamin D supplementation may reduce the risk or severity of infection, but this has been investigated in few large population-based trials. We analyzed data from the D-Health Trial, using prescription of antibiotics as a surrogate for infection. Methods The D-Health Trial is a randomized, double-blind, placebo-controlled trial in which 21 315 Australians aged 60–84 years were randomized to 60 000 IU of supplementary vitamin D3 or placebo monthly for 5 years. For this analysis, the primary outcome was the number of antibiotic prescription episodes; secondary outcomes were total number of prescriptions, repeat prescription episodes, and antibiotics for urinary tract infection. We estimated incidence rate ratios (IRRs) using negative binomial regression, and odds ratios using logistic regression. Results Vitamin D supplementation slightly reduced the number of prescription episodes (IRR, 0.98; 95% confidence interval [CI], .95–1.01), total prescriptions (IRR, 0.97; 95% CI, .93–1.00), and repeat prescription episodes (IRR, 0.96; 95% CI, .93–1.00). There was stronger evidence of benefit in people predicted to have insufficient vitamin D at baseline (prescription episodes IRR, 0.93; 95% CI, .87–.99). Conclusions Vitamin D may reduce the number of antibiotic prescriptions, particularly in people with low vitamin D status. This supports the hypothesis that vitamin D has a clinically relevant effect on the immune system. Clinical Trials Registration Australian New Zealand Clinical Trials Registry: ACTRN12613000743763. https://www.anzctr.org.au/. Supplementing older Australians with 60 000 of vitamin D per month resulted in slightly fewer antibiotic prescriptions compared with those randomized to placebo, particularly in those predicted to have low vitamin D status at baseline.