The main variable of interest is 25(OH)D as it best reflects vitamin D stores. Based on prior pilot data, the mean (SD) expected 25(OH) among HIV-infected subjects is 21 (11) ng/ml. The sample size in the present study has 80% power to detect change in 25(OH) D of 8 ng/ml with alpha=0.05. Analysis of covariance based on a general linear regression model will then be used to determine whether any possible group differences remain after controlling for other factors such as race, sex, estimated dietary intake of Vitamin D and sunlight exposure (using month of study as surrogate for sunlight exposure).