Prevention of urinary tract infections with vitamin D supplementation 20,000 IU per week for five years. Results from an RCT including 511 subjects

Abstract

Background: In observational studies vitamin D deficiency is associated with increased risk of infections, whereas the effect of vitamin D supplementation in randomized controlled trials is non-conclusive.

Methods: Five hundred and eleven subjects with prediabetes were randomized to vitamin D₃ (20,000 IU per week) versus placebo for five years. Every sixth month, a questionnaire on respiratory tract infections (RTI) (common cold, bronchitis, influenza) and urinary tract infection (UTI) was filled in.

Results: Mean baseline serum 25-hydroxyvitamin D (25(OH)D) level was 60 nmol/L. Two hundred and fifty-six subjects received vitamin D and 255 placebo. One hundred and sixteen subjects in the vitamin D and 111 in the placebo group completed the five-year study. Eighteen subjects in the vitamin D group and 34 subjects in the placebo group reported UTI during the study (p < 0.02), whereas no significant differences were seen for RTI. The effect on UTI was most pronounced in males. The effect of vitamin D on UTI was unrelated to baseline serum 25(OH)D level.

Conclusion: Supplementation with vitamin D might prevent UTI, but confirmatory studies are needed.

Keywords:

• Diabetes
• respiratory infection
• urinary tract infection
• vitamin D

Acknowledgements

The superb assistance from the staff at the Clinical Research Unit (and in particular Aslaug Jakobsen) and the Department of Medical Biochemistry at the University Hospital of North Norway is gratefully acknowledged.

Disclosure statement

The authors do not have a commercial or other association that might pose a conflict of interest.

Funding information

The study was supported by grants from the Novo Nordisk foundation (grant number R195-A16126), the North Norway Regional Health Authorities (grant number 6856/SFP1029-12), UiT The Arctic University of Norway, the Norwegian Diabetes Association, and the Research Council of Norway (grant number 184766).