Vitamin D Deficiency

Low levels of vitamin D are common among HIV positive people around the world, according to a set of studies presented at CROI. Vitamin D deficiency promotes bone loss -- a concern for people with HIV, who are already at higher risk than the general population -- and has been linked to cardiovascular disease, cancer, and other conditions.

In an analysis of 672 participants (about 75% men) in the CDC's SUN Study (abstract 750), which includes individuals with generally well-controlled HIV disease at clinics in four U.S. cities, 72% were found to have insufficient blood levels of 25-hydroxyvitamin D (<30 ng/mL); none were receiving vitamin D supplements.

Looking at U.S. women (abstract 754), a cross-sectional analysis of 609 participants (79% HIV positive, 21% HIV negative) in the Women's Interagency Health Study found that 60% had vitamin D deficiency (<20 ng/mL) and 24% had insufficiency (<30 ng/mL). Worsening deficiency was strongly linked to higher risk for bacterial vaginosis (disruption of the normal balance of microorganisms in the vagina).

Turning to Europe, in a retrospective analysis of 211 participants (75% men) in the Swiss HIV Cohort (abstract 752), vitamin D deficiency rates before starting ART were not so high (14% if tested during the fall and 42% if tested during the spring); percentages were similar one year after starting ART. In an analysis of 856 HIV positive participants in the Italian ICONA cohort (70% on ART, 30% prior to ART initiation), 54% had vitamin D insufficiency and 7% had deficiency (abstract 751).

Finally, in a study looking at the link between vitamin D levels and health outcomes among women in Tanzania (abstract 753), women with low levels (<32 ng/mL) had a 192% higher risk of vaginal candidiasis (thrush), a 45% higher likelihood of wasting, and a 28% higher risk of upper respiratory infections.

Vitamin D is produced by the body when the body is exposed to sunlight, and is available in foods such as coldwater fish and fortified dairy products. While deficiency risk factors varied somewhat across these studies, researchers consistently found greater insufficiency during seasons with less sunny weather and in climates where people received less sun exposure, and among people with darker skin; people who used NNRTIs also were more likely to be deficient that those using protease inhibitors.

While these vitamin D insufficiency rates are alarming, they may not be much higher than those of the HIV negative general population; in the U.S. for example, it is estimated that as many as three-quarters of the population may not get enough. Researchers are increasingly aware that vitamin D deficiency is more common than previously assumed, and many experts believe current recommended levels should be increased.

Liz Highleyman (liz@black-rose.com) is a freelance medical writer based in San Francisco.