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Vitamin D supplementation may prevent urinary tract infections

Posted on: August 8, 2016   by  Amber Tovey


A five year-long randomized controlled trial (RCT) discovered that vitamin D supplements helped prevent UTIs.

A urinary tract infection (UTI) may affect any part of the urinary system, the kidneys, ureters, bladder and urethra. Most UTIs involve the lower urinary tract, which is composed of the bladder and the urethra.

Women face the greatest risk of developing a UTI, with an estimated 50% chance of experiencing a UTI in their lifetime. However, men can also be affected by UTIs. The symptoms include a burning sensation during urination, frequent or intense urge to urinate, pain or pressure in the lower abdomen, back pain, feeling tired and fever. When treated properly with antibiotics, lower UTIs rarely lead to complications. Though, when left untreated, a UTI may lead to serious consequences, including permanent kidney damage and sepsis.

Research has shown that vitamin D helps fight infection by increasing the production of antimicrobial peptides. These peptides assist the body in destroying the cell walls of viruses and bacteria. A case-control study discovered that children with UTIs had significantly lower vitamin D levels than healthy children. Furthermore, the study found that children with vitamin D levels below 20 ng/ml were 3.5 times more likely to experience a UTI.

The relationship between low vitamin D levels and UTIs led researchers from Norway to investigate whether vitamin D supplementation prevents UTIs. In addition to investigating the effects of vitamin D supplementation on UTIs, researchers also wanted to determine how vitamin D affects the incidence of respiratory tract infections (RTIs), since the researchers thought vitamin D would likely play a similar role in the two.

A total of 511 pre-diabetic participants were randomly divided to receive 20,000 IU of vitamin D per week or placebo for five years. Every six months, the participants filled out a questionnaire on respiratory tract infections (RTIs) and urinary tract infections (UTIs). If the participant was diagnosed with type II diabetes at any time during the study, their involvement in the study ended.

After a five-year intervention, here is what the researchers found:

  • The baseline vitamin D levels were 23.9 ng/ml and 24.4 ng/ml in the vitamin D group and placebo group, respectively.
  • The vitamin D levels increased in the vitamin D group to an average of 48.8 ng/ml after five years; the placebo group’s vitamin D levels remained stable.
  • During the study, 153 participants in the vitamin D group dropped out due to an illness or the development of type II diabetes.
  • No significant differences in adverse events were recorded.
  • A total of 141 UTI events were recorded during the five-year investigation. Forty-four (18 incident and 26 recurrent) in the vitamin D group and 97 (34 incident and 63 recurrent) in the placebo group (p < 0.05).
  • When grouped by gender, the occurrence of UTI was significantly less in the vitamin D group compared to the placebo group among men. However, the difference was insignificant among women.
  • Vitamin D did not affect the occurrence of RTIs.

The researchers concluded,

“In the present study, we have found supplementation with vitamin D to significantly reduce the occurrence and number of UTI during a five-year intervention study, whereas no effect was seen on RTI.”

The researchers acknowledge the study’s main limitation; the study relied on a questionnaire with self-reported occurrence of infections without any bacteriological verification. Any study that uses self-reports to measure the outcome enables recall bias. However, the study possessed a few key strengths as well. The study strictly followed a RCT design, which allowed the study to prove causation. A large number of participants were included into the study, making the study more powerful. Additionally, the study was conducted over a long period of time. Lastly, the researchers measured vitamin D levels before and after the intervention, showing that the vitamin D group achieved sufficiency and the placebo group remained deficient. As the researchers point out, further RCTs are needed to confirm these findings.


Tovey, A & Cannell, JJ. Vitamin D supplementation may prevent urinary tract infections. The Vitamin D Council Blog & Newletter, 2016.


Rolfe J. et al. Prevention of urinary tract infections with vitamin D supplementation 20,000 IU per week for five years. Results from an RCT including 511 subjects. Infectious Diseases, 2016.

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