The findings were published recently in the journal Clinical Nutrition.
Ezeamama conducted an 18-month longitudinal study in which the immune status of 398 HIV-positive adults was measured at 0, 3, 6, 12 and 18 months. The researchers, through observation, related the rise in immune function to whether or not individuals had adequate levels of vitamin D.
Specifically, Ezeamama found that vitamin D helped the adults' CD4+T cells recover more quickly. CD4+T cells are a type of T cell that helps the immune system fight off pathogens. For HIV-positive adults, CD4+T cells are critical because of their weakened immune systems.
Ezeamama found that participants with sufficient levels of vitamin D recovered more of their immune function -- on average 65 CD4+T cells more -- than those with vitamin D deficiency. The benefit of vitamin D sufficiency seemed greater for younger and underweight HIV-positive adults.
"HIV destroys the capacity of the body to mount effective response to pathogens," Ezeamama said. "Given different vitamin D levels, HIV-positive adults recovered at different rates. We found a relationship between vitamin D and CD4+T cells."