Vitamin D Protects Against Tuberculosis
02.23.06, 12:00 AM ET
THURSDAY, Feb. 23 (HealthDay News) -- Discovery of the molecular mechanism
that the body uses to fight off tuberculosis could open the way to use of
ordinary vitamin supplements to help prevent the disease, researchers report.
The finding also helps explain why blacks are more vulnerable than whites
to tuberculosis and why they develop more severe cases when infected,
according to a study in the Feb. 23 online issue of Science.
The story starts about a decade ago, when research revealed that the immune
system of fruit flies produces a protein that attacks bacteria and fungi,
explained study author Dr. Robert L. Modlin, chief of dermatology at the
University of California, Los Angeles.
"In 1999, it became clear that there were equivalents in humans, a family
of proteins," Modlin said. "Each recognizes a defined biochemical from a
bacterium or virus."
Studies showed that in mice, the defense involved production of nitric
oxide to fight infection. However, that was not found to happen in human
cells, Modlin said.
Four years of work led to the finding that the human defense mechanism
involves vitamin D, he said. White blood cells are stimulated to convert
ordinary vitamin D -- which is produced, in large part, by exposure to
sunlight -- into an active form that is used to make a protein that kills
the tuberculosis bacteria.
"Our other main finding was that African-Americans, who are known to be
more susceptible to tuberculosis, have lower levels of vitamin D in their
blood," Modlin said. Melanin, the pigment that darkens skin, absorbs the
ultraviolet rays of sunlight, reducing vitamin D production in blacks, he
Cells grown in blood serum from black individuals produced 63 percent less
of the bacteria-fighting protein than those grown in blood serum from white
people. Adding vitamin D to the cultures increased production of the
protein, Modlin said.
One question raised by the discovery is whether giving vitamin D to humans
can do the same thing, he said, adding, "Were hoping this paper will raise
interest in that."
If the vitamin does have a protective effect, "a vitamin D supplement I
think is the way to go," Modlin said. As a dermatologist, he noted, he is
acutely aware of the damage that can be done by overexposure to sunlight.
However, "I can't recommend that people take vitamin D supplements yet,"
Modlin said. "We need to do more studies." His group is doing studies along
that line, looking at "what effects vitamin D might have on the immune
There's a possibility that the work might have implications beyond
tuberculosis, Modlin said. "Our results indicate we have much yet to learn
about human immune responses to infections," he said.
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