A potential influence of vitamin D on HIV infection and bone disease in HIV-positive patients

Vitamin D has long been recognized as essential to the skeletal system. Newer evidence suggests that it also protect against cancer, heart disease, fractures and falls, type 2 diabetes, and depression and play a major role regulating the immune system. Vitamin D polarizes the adaptive immune system away from Th-1 and toward Th-2 responses, and enhances innate immunity. Though vitamin D's anti-viral mechanism has not been fully established, it may be linked to vitamin D's ability to up-regulate the anti-microbial peptides.Vitamin D deficiency is prevalent among patients with HIV infection. An inverse association between 1,25(OH)2D concentrations and mortality has been reported, and some cross-sectional studies have indicated positive correlations between 1,25(OH)2D and CD4− cell counts.Vitamin D deficiency, low bone mineral density (BMD) and increase in fracture risk have emerged as subjects of concern in HIV-positive patients. Efavirenz is associated with a reduction in 25OHD levels, tenofovir with secondary hyperparathyroidism, and ART, irrespective of the drugs used in the regimen, with increased bone turnover and low BMD. Although the incidence of fractures seems to be increased in HIV-positive patients, the contribution of vitamin D deficiency to these fractures remains uncertain.The benefits of vitamin D supplementation in HIV-positive patients need to be demonstrated in interventional studies. The associations between low levels of 25OHD and many chronic conditions that are prevalent among HIV-infected persons highlight the need for routine screening for vitamin D deficiency, and the benefits of a universal ‘test and treat’ strategy in HIV-infected individuals remain to be defined.