By David Templeton, Pittsburgh Post-Gazette
A University of Pittsburgh study links bacterial vaginosis in pregnant women to a deficiency of vitamin D.
"Bacterial vaginosis affects nearly one in three reproductive-aged women, so there is great need to understand how it can be prevented," said Lisa M. Bodnar, the Pitt assistant professor of epidemiology obstetrics and gynecology. The infection "is not only associated with a number of gynecologic conditions, but also may contribute to premature delivery -- the leading cause of neonatal mortality -- making it of particular concern to pregnant women."
Published this week in the Journal of Nutrition, the study also notes that African-American women are three times more likely than Caucasian women to have BV in part because darker skin pigmentation does not as readily convert sunlight into vitamin D.
Poor diet and obesity also contribute to a vitamin D deficiency.
The Pitt study used blood tests from 469 pregnant women to determine whether poor vitamin-D status played a role in predisposing women, and especially African Americans, to BV.
Dr. Bodnar and her colleagues at the Magee-Womens Research Institute in Oakland discovered that 41 percent of study participants had BV, and 93 percent of those with BV had insufficient levels of vitamin D. They also found that BV prevalence decreased as vitamin D levels rose.
"It was a purely observational study," Dr. Bodnar said. "We didn't give any vitamin D to participants."
Even though BV was more prevalent in African-American women, the study found that Caucasian women with low blood levels of vitamin D were equally susceptible to infection. Caucasians, though, are less likely to be deficient in the vitamin.
"Ninety percent of vitamin D comes from sunlight," Dr. Bodnar said. "So when that high a proportion comes from sunlight and something as basic as skin color prevents it from transforming light into vitamin D, it emerges as the No. 1 reason for BV."
Diet also is a factor in BV prevalence in women, especially in African Americans, who are less likely to meet dietary recommendations for the vitamin. Milk is the most common source of vitamin D, but African-American women have a higher rate of lactose intolerance than Caucasians.
"There are not very many foods high in vitamin D, and those that are are expensive, including fatty fish, which many people can't afford," Dr. Bodnar said.
Optimal levels of vitamin D have yet to be established. For that reason, the study does not encourage women to begin taking mega-doses of vitamin D. Instead it recommends that women discuss their level of vitamin D with their physicians.
But women planning a pregnancy or already pregnant should take a prenatal vitamin, which typically includes 400 international units of vitamin D. "Vitamin D has no adverse effects, is inexpensive, easy to take and is acceptable to people," Dr. Bodnar said.
For now, interest in vitamin D "is hot," she said. Vitamin D deficiency has been linked to problems with immune response and increases in cancer rates, cardiovascular disease, osteoporosis, diabetes and mental health problems.
"Bacterial vaginosis is another outcome to put on that list," she said.
Future Pitt studies, she said, will help determine whether vitamin D supplements can reduce infant mortality and other health problems affecting mothers and babies.
Dr. Bodnar's team recently received National Institutes of Health funding to study a large number of women, their vitamin D levels and rates of pre-term birth and pre-eclampsia -- pregnancy-induced hypertension accompanied by protein in the urine.
That study will help determine whether vitamin D deficiency increases the r