Women with the reproductive infection bacterial vaginosis (BV) do not benefit from high-dose vitamin D supplementation, according to new research. The findings add to a body of conflicting data about a possible link between vitamin D (a powerful immune system regulator) and BV, which is the most common vaginal infection among women ages 15 to 44 around the world.

“Earlier studies observed that women with low vitamin D levels were more likely to have bacterial vaginosis, and we hypothesized that vitamin D supplementation might reduce BV,” said the trial’s lead author Abigail Norris Turner, PhD, an infectious disease expert at The Ohio State University Wexner Medical Center. “However, our study found that high-dose vitamin D supplementation wasn’t helpful in preventing recurrence of BV.”

BV is caused by an imbalance in the bacteria that normally populate the reproductive tract, and is not sexually transmitted. Initial antimicrobial treatment is usually successful, but many women go on to have repeat episodes of BV. Some women don’t have symptoms, while others have symptoms that sufferers say are embarrassing and detrimental to their sexual relationships.

Beyond embarrassment, BV has much more serious health implications: in pregnant women, it can cause spontaneous abortions, and women who have BV are more susceptible to acquiring and transmitting HIV. In the US, 21 million women are diagnosed with BV each year, and black women are almost twice as likely to have the condition as white women.

“BV is a very real health issue for millions of women, many of whom have limited access to medical care,” said Turner, who was originally an HIV epidemiologist before turning her focus to women’s reproductive health more generally. “Finding a low cost, simple way to help women with recurrent BV would be a major global public health win.”

The Silver Lining

For the randomized, double-blinded study, published in the American Journal of Obstetrics and Gynecology, Turner enrolled 118 women with BV from a local health department sexual health clinic. At enrollment, the women had their baseline vitamin D level measured via a blood sample, and were provided with the standard, CDC-recommended 7-day antimicrobial treatment for BV.

The women were randomized into 2 equal-sized groups, with 1 group receiving 9 doses of 50,000 IU of cholecalciferol (vitamin D3), and the other group receiving a placebo. Both groups were instructed to take either the vitamin D tablets or placebo at regular intervals during the 24-week study. Study participants’ BV status and vitamin D serum levels were checked at several points across the study. None of the participants, investigators, nor data analysts knew which women were receiving vitamin D and which were receiving placebo.

Turner found that while women randomized to the vitamin D arm had significant increases in their serum vitamin D levels compared to women in the placebo arm (validating their compliance with the protocol), this did not translate into a decrease in BV recurrence. Despite not finding the evidence that she was looking for, Turner said that her research yielded other important findings for future studies.

“We learned that this high-risk population knew a lot about bacterial vaginosis, and that many women have an active interest in learning more about treating it,” said Turner, who was supported by a KL2 career development grant from Ohio State’s Center for Clinical and Translational Science (CCTS). “This study also gave us proof that we can effectively recruit for a large-scale clinical trial at a local health clinic.”

Moving Beyond Vitamin D

Turner and her research mentor, Rebecca Jackson, MD, emphasize that while vitamin D may not be useful for treating women with recurrent BV, the jury is still out on the vitamin’s ability to prevent BV from initially developing.

“Vitamin D is critical to a healthy immune system, so there may still be a role for it from a prevention standpoint,” said Jackson, a women’s health expert and director of the CCTS. “And certainly, women of all ages should make sure they are getting adequate amounts of vitamin D through diet, daily exposure to sunlight or supplementation.”

Turner says that while she is able to rule out vitamin D as a solution for recurrent BV, the disappointing results have pushed her to pursue a different track.

“I think we need to go back to why people studied vitamin D as a BV risk factor initially – and that’s the immune system and immune response,” said Turner. “Most women have continually fluctuating concentrations of ‘good’ and ‘bad’ bacteria in the genital tract. What immune factors lead some women to develop BV, and others to more effectively regulate the balance of bacteria in the vagina?”

Turner is in the process of developing a grant proposal to explore her hypothesis further.

Turner’s research was supported by a grant from the National Institute of Allergy and Infectious Diseases. Study collaborators include, from Ohio State’s College of Medicine: Patricia Carr Reese, MPH and John A. Davis, MD, PhD, Division of Infectious Disease; Mark A. Klebanoff, MD, MPH, Departments of Pediatrics and Obstetrics and Gynecology and the Research Institute at Nationwide Children’s Hospital; from the Sexual Health Clinic of the Columbus Public Health Department: Karen S. Fields, RN, Julie Anderson, MPH, Melissa Ervin, MT (ASCP), and Mysheika Williams Roberts, MD, MPH; from the Department of Obstetrics, Gynecology, and Reproductive Biology, Laboratory of Genital Tract Biology, Brigham and Women’s Hospital, Harvard Medical School: Raina N. Fichorova, MD, PhD.

The above story is reprinted from materials provided by the Ohio State University Center for Clinical and Translational Science via Newswise.

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