Vitamin D has been touted as a preventive treatment or therapy for multiple ailments, from brittle bones to cancer to autoimmune disorders. Several studies have suggested that individuals living with HIV who supplement their diets with vitamin D have a lower risk of developing Type 2 diabetes and elevated cholesterol levels, both of which are not uncommon in those with HIV who are being treated with antiretroviral therapy (ART). With this in mind, a team of scientists from the University of Alabama-Birmingham and other institutions set out to learn whether vitamin D had any positive effect on lipid levels and insulin resistance in HIV-positive individuals who were just beginning ART regimens.
The team enrolled 165 subjects in its double-blind study. The subjects were randomly assigned to either of 2 groups, one that received supplemental vitamin D and calcium and one that was given a placebo. The subjects’ vitamin D, glucose, insulin, and cholesterol levels, and BMI and waist circumference were measured at the beginning of the study (baseline), and at weeks 24 and 48 after ART had been initiated.
Both groups of subjects experienced significant increases in their cholesterol levels at week 24 and again at week 48, as well as moderate increases in their glucose levels over the course of the study. The placebo group saw insulin levels rise during the first 24 weeks while the vitamin D group did not, but neither group had statistically significant changes by week 48. Subjects in the placebo group experienced a slight increase in waist circumference as measured at weeks 24 and 48, but the increase was not statistically significant. Neither were the differences in BMI measured in the 2 groups.
“Despite the marked increase in vitamin D levels from the time of ART initiation and benefits regarding bone health, high-dose vitamin D and calcium supplementation did not meaningfully improve relevant metabolic parameters, including glucose metabolism, insulin resistance, lipid profiles, body composition measures, or prevalence of the metabolic syndrome,” the authors wrote in their study conclusions, adding, “Despite having low vitamin D levels throughout the study, participants in the placebo arm had only modest changes in the metabolic parameters measured.”
Why doesn’t vitamin D, given its beneficial effects on bone health, lower lipid levels and reduce insulin resistance in HIV-positive individuals who begin ART regimens? “It may be that metabolic changes related to ART initiation far outweigh the effects of vitamin D supplementation,” the authors wrote. “Alternatively, vitamin D supplementation may only be useful in persons who develop these metabolic derangements after some duration of exposure to the ART medications or that the [serum] level of [vitamin] D required to cause metabolic derangements is lower than that needed to maintain bone health.”
Limitations of this study include a short follow-up period (1 year), and the fact that the team used only 1 type of ART regimen consisting of efavirenz, emtricitabine, and tenofovir disoproxil fumarate on its subjects; a different medication regimen potentially could have changed the results. In addition, the subjects were young and otherwise healthy, which raises the question of whether vitamin D supplementation might have had a different impact on an already metabolically-impaired population. The exercise, alcohol, and smoking habits of the subjects were similarly unknown. In addition, women, who have been shown to be responsive to vitamin D supplementation in previous studies, were underrepresented in this trial.
By Laurie Saloman