Sunshine May Provide Prostate Protection
Prostate Cancer Risk Linked to Vitamin D From Sunlight
June 15, 2005 -- Sun-exposed white men are less likely to get prostate cancer than their less tanned brethren, a new study shows.
That's no reason for men to recklessly sunbathe. The greater a person's
lifetime sun exposure, the greater a person's risk of skin cancer. But the
finding does indicate that vitamin D -- which humans can get from sun exposure
-- protects against prostate cancer.
Also protective are genes that let some people's bodies use vitamin D more
efficiently, find Esther M. John, PhD, of the Northern California Cancer
Center; Gary G. Schwartz, PhD, of Wake Forest University, and colleagues.
"It's a pretty impressive finding," Schwartz tells WebMD. "Men
with high solar exposure had their risk of prostate cancer cut in half. This
leaves us with even greater confidence that vitamin D deficiency really does
increase a man's risk of prostate cancer."
The findings appear in the June 15 issue of Cancer Research.
Vitamin D Detective Finds Prostate Cancer Clue
Schwartz first proposed a link between prostate cancer and vitamin D in
1990. That's when he noticed that the populations most likely to get too little
vitamin D are the same populations most likely to get prostate cancer.
"Prostate cancer is more common in northern latitudes, in blacks, and in
the elderly. That resembles essentially the same people who most often got what
used to be called rickets, a bone-deforming disease linked to lack of exposure
to sunlight," Schwartz says. "So I argued that if vitamin D deficiency
causes one disease -- rickets -- there is no reason why it cannot cause another
disease -- prostate cancer -- later in life."
People living in the north and elderly people tend to get less time in the
sun than young people living in southern climes. Unlike other vitamins, a
person's main source of vitamin D isn't food; it's sunshine. The body makes its
own vitamin D, but only when it's exposed to the sun.
Vitamin D is made from sunlight acting on the skin," Schwartz says.
"Eighty percent to 90% of vitamin D in the body is derived from sunlight,
not from diet."
Additional evidence of a vitamin D-prostate cancer link came from laboratory
studies. Schwartz and colleagues found that prostate cancer cells are less
likely to behave like cancer cells when exposed to vitamin D.
Moreover, Schwartz notes that prostate cells are able to process vitamin D.
In fact, the surface of a prostate cell bears a molecule called a vitamin D
receptor or VDR. When vitamin D plugs into one of these receptors, it sets off
a complex chain of events thought to protect the cell against cancer.
But when other researchers looked at whether sun exposure and vitamin D
levels were linked to prostate cancer, they got mixed results. Some found a
link. Others did not. Clearly, something else is going on.