HIV-positive people with vitamin D deficiency were far more likely to also have type 2 diabetes than people who were not vitamin D deficient, according to a study published online December 20 in the journal AIDS.

Poor vitamin D levels in people with HIV have become a prominent concern among AIDS researchers in recent years. Vitamin D deficiency has been linked to a number of health conditions in HIV-negative people, including: poor bone strength and density, type 2 diabetes, metabolic syndrome and cardiovascular disease (CVD).

A number of recent studies have also consistently found that vitamin D levels are deficient in a significant number of people living with HIV in the Northern Hemisphere. What remains unclear, however, is whether HIV and its treatment are solely responsible for the increase in diseases such as diabetes and CVD seen in HIV-positive people, or whether low vitamin D levels also contribute in a meaningful way.

To begin answering these questions, Zsofia Szep, MD, from the University of Pennsylvania Medical School in Philadelphia, and her colleagues tested vitamin D levels in participants enrolled in the Modena HIV Metabolic Clinic Cohort in Italy. Their aim was to determine whether vitamin D deficiency was linked to either type 2 diabetes or metabolic syndrome. Metabolic syndrome involves having a large waist circumference and problems with cholesterol and triglycerides and blood sugar control, and it is a significant risk factor for diabetes, heart attacks and strokes.

Among the 1,405 participants in the study, most were male and the average age was 44. About 45 percent were also infected with hepatitis C virus (HCV), but few were taking vitamin D supplements.

Overall, Szep and her colleagues found that 62 percent of the study participants had vitamin D deficiency—defined as blood levels of 25-hydroxyvitamin D less than 20 nanograms per milliliter (ng/ml). An additional 20 percent had vitamin D insufficiency—blood levels of vitamin D of at least 20 ng/ml but less than 30 ng/ml.

When Szep’s team accounted for a number of factors that can contribute to type 2 diabetes—such as sex, age, body mass index and HCV coinfection—vitamin D deficiency remained strongly associated with type 2 diabetes. In fact, vitamin D deficiency predicted the presence of type 2 diabetes more than any other factor, and people with vitamin D deficiency were 85 percent more likely to have diabetes than people who weren’t deficient.

As far as metabolic syndrome, there was a trend toward association—people with vitamin D deficiency were 32 percent more likely to have metabolic syndrome—but this did not reach statistical significance. This means that the difference was small enough that it could have occurred by chance.

The authors acknowledge that the study design, which involved a snapshot of people’s health at a single point in time, can’t establish whether vitamin D deficiency causes diabetes or whether the link is coincidental. However, they note that maintaining good vitamin D levels is associated with reducing blood vessel inflammation in HIV-negative people. Given that HIV itself significantly increases inflammation—a precursor to diabetes and CVD—it is possible that HIV levels and vitamin D levels are synergistically contributing to these health problems.

“Future studies should examine whether vitamin D supplementation can prevent or treat type 2 diabetes mellitus in HIV and possibly reduce complications associated with HIV infection and its treatment,” the authors conclude.