Vitamin D is important for cell growth, immunity, and metabolism. Vitamin D deficiency has classically been associated with rickets and decreased bone density and more recently with increased risk and severity of autoimmune diseases, cancers, myocardial infarction, diabetes, and infectious diseases. The active form of vitamin D (vitamin D3) has been implicated recently in an intracellular process known as autophagy. HIV-1 reduces autophagy during permissive infection and that agents that induce autophagy, including vitamin D3, can inhibit HIV-1 replication. These findings help provide a biological explanation for the increased risk of more rapid disease progression observed in HIV-infected persons with low levels of vitamin D or with genetic variants within the vitamin D receptor that alter binding to vitamin D. HIV itself can also affect levels of vitamin D. Furthermore the vitamin is metabolized by the body in the same way as many anti-HIV drugs, using the P450 pathway, and some earlier research had suggested that protease inhibitors can inhibit the body’s ability to metabolize vitamin D2. Persons with HIV infection frequently have low vitamin D levels3. Moreover, patients treated with non-nucleoside reverse transcriptase inhibitors and protease inhibitors are at increased risk of vitamin D deficiency4. Thus, vitamin D deficiency is common in HIV-infected persons regardless of treatment status, viral load, or D4+ lymphocyte count.
