High-dose vitamin D supplementation can boost immune response to help the body fight infections like HIV, a new study has found.
"Vitamin D may be a simple, cost-effective intervention, particularly in resource-poor settings, to reduce HIV-1 risk and disease progression," the researchers said.
The study looked at two ethnic groups in Cape Town to see how seasonal differences in exposure to ultraviolet B radiation, dietary vitamin D, genetics, and pigmentation affected vitamin D levels, and whether high-dose supplementation improved deficiencies and the cell's ability to repel HIV-1.
Cape Town has a seasonal ultraviolet B regime and one of the world's highest rates of HIV-1 infection, making it an appropriate location for a study like this one, according to Nina Jablonski, Evan Pugh Professor of Anthropology, Penn State, who led the research.
One hundred healthy young individuals, divided between those of Xhosa ancestry - whose ancestors migrated from closer to the equator into the Cape area - and those having Cape Mixed ancestry - a complex admixture of Xhosa, Khoisan, European, South Asian and Indonesian populations - were recruited for the study.
The Xhosa have the darkest skin pigmentation, while the Khoisan, the original inhabitants of the Cape are lighter skinned. The Cape Mixed population falls between the Xhosa and Khoisan in skin pigmentation levels.
Cape Town is situated in the southern hemisphere at about the same distance from the equator as the Florida panhandle, slightly more than 30 degrees latitude.
Ultraviolet B levels show a winter decline anywhere above 30 degrees latitude, so Cape Town has a definite winter with low levels of the ultraviolet B wavelengths needed to produce precursor vitamin D3.
The researchers found that both groups exhibited vitamin D deficiency during the winter, with women in both groups being more deficient, on average, than the men.
Because of vitamin D's impact on the immune system, the researchers provided six weeks of supplemental vitamin D3 to 30 of the Xhosa participants, which brought 77 per cent of the participants to optimal vitamin D status.
To test how vitamin D status affected the immune system and HIV-1 in particular, the researchers exposed blood samples from Xhosa and Cape mixed participants taken during the summer and winter when the subjects were vitamin D sufficient or deficient.
They found that after nine days, the winter blood samples had greater infection than those taken in summer. After six weeks of vitamin D supplementation, the Xhosa blood sample levels of HIV-1 infection were the same as those during the summer.
"High-dosage oral vitamin D3 supplementation attenuated HIV-1 replication, increased circulating white blood cells and reversed winter-associated anaemia," the researchers said.