Vitamin D critical to human TB response

Vitamin D plays a critical role in the human body's response to tuberculosis, according to new research that explains why people of African descent are more susceptible to TB.

The research also suggests a new way to fight one of the world's deadliest diseases: with a simple dietary supplement.

Tuberculosis, usually caused when a person inhales tuberculosis bacteria, killed an estimated 1.7 million people in 2003 and is the leading cause of death for people afflicted with AIDS, according to the World Health Organization (WHO).

People of African descent are more susceptible to tuberculosis than Caucasians, with higher rates of infection and more severe cases once infected, trends that had puzzled researchers until now. Sub-Saharan Africa, for example, has the world's highest per capita rates of both tuberculosis cases and deaths from the disease, roughly twice the next-highest region, according to WHO statistics.

The research, conducted by a team from the University of California, Los Angeles (UCLA), and the Harvard School of Public Health, shows that vitamin D plays a key role in the production of a molecule called cathelicidin, which kills the tuberculosis bacteria.

The body produces vitamin D when sunlight hits the skin. The skin pigment melanin - more abundant in darker skin - shields the body from the sun's rays, reducing damage from ultraviolet light, but also reducing vitamin D production.