A randomized controlled trial has discovered that vitamin D supplementation is an effective treatment for asymptomatic bacterial vaginosis.

Bacterial vaginosis (BV) is an infection that results from the overgrowth of a type of bacteria in the vagina, upsetting the natural balance of bacteria. It’s the most common vaginal infection in women between the ages of 15 and 44.

Asymptomatic BV means the patient doesn’t experience any symptoms. However, the lack of symptoms doesn’t mean that the patient will not experience any complications. BV increases the risk for preterm labor and low birth weight babies, even in asymptomatic infections.

Vitamin D increases the expression of cathelicidin, a protein that destroys bacteria. This has led researchers to hypothesize that vitamin D deficiency may lead to BV. But research has not provided consistent evidence to support this theory.

Researchers from Iran recently conducted a double-blind, randomized, controlled trial on the effectiveness of vitamin D supplementation to eliminate asymptomatic BV among reproductive women with vitamin D deficiency.

Before enrollment, the researchers used the Nugent score to diagnose BV. The Nugent score calculates a number ranging from 0 to 10 based on the presence of certain types of bacteria.

The researchers screened 218 women with asymptomatic BV for vitamin D deficiency, which they defined as levels less than 30 ng/mL. A total of 211 women (97 percent) were considered to be vitamin D deficient, and thus were enrolled into the study.

The women were randomly divided into two groups: a placebo group and a vitamin D group.

The vitamin D group received two drops of liquid vitamin D, totaling 2,000 IU daily. The placebo group received two drops of sesame oil daily. Treatment lasted for 15 weeks.

After week 15, the researchers re-evaluated vitamin D status and the Nugent score to determine whether vitamin D supplementation cured asymptomatic BV. Here is what they found:

• The vitamin D levels increased from an average of 9.4 ng/mL to 28.4 ng/mL in the vitamin D group.

• The vitamin D levels barely increased from an average of 8.9 ng/mL to 9.3 ng/ml in the placebo group.

• The cure rate of asymptomatic BV was 63.5 percent in the vitamin D group and 19.2 percent in the placebo group (P < 0.001).

• Marital status, menstrual phase at time of sampling, and smoking had significant relationships with BV. After controlling for these variables, the odds of BV positive results in the placebo group was 10.8 times higher than in the intervention group (P < 0.001).

The researchers stated, “In conclusion, the treatment of vitamin D deficiency using 2,000 IU/day edible vitamin D for 15 weeks was an effective way to cure the asymptomatic BV … We recommend vitamin D therapy for the prevention or management of BV among deficient women. By treating vitamin D deficiency, preterm labour and other adverse effects of BV may be prevented.”

The major strength of the study was its repeated measurement of vitamin D status at baseline and after treatment.

Another strength was that the researchers only enrolled vitamin D deficient women.

Also, the study design was able to prove causality rather than only association.

Conversely, the researchers did not measure immune markers to illustrate a mechanism for vitamin D’s positive effects on BV. Also the dose was only 2,000 IU/day and final mean 25(OH)D levels in the treatment group did not exceed 30 ng/ml.

This type of study needs to be done using 5,000 to 10,000 IU/day.