Adequate
levels may help keep cell growth in check, but researchers say more study
needed
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WebMD News from HealthDay
By Brenda
Goodman
HealthDay
Reporter
THURSDAY, May 1,
2014 (HealthDay News) -- Low blood levels of vitamin D may be linked to more
aggressive and advanced cases of prostate cancer in men, a new study suggests.
And black men
with low vitamin D levels were more likely than those with normal levels to
test positive for cancer after a prostate biopsy.
The study,
published May 1 in
the journal Clinical Cancer Research, suggests that vitamin D may play
an important role in how prostate cancer starts and spreads, although it does
not prove a cause-and-effect relationship. Researchers aren't yet sure exactly
how it comes into play or even if taking extra vitamin D might keep prostate
cancer in check.
"There are
still many questions about this relationship that have to be answered,"
said Dr. Len Lichtenfeld, deputy chief medical officer at the American Cancer
Society. He was not involved in the research.
"We really
don't know, for certain, what role vitamin D plays in cancer -- either the
genesis or beginning of cancer -- or in defining how aggressive the cancer may be,"
he said. "Further research has to be done."
What is known is
that vitamin D plays several critical roles in how cells develop and grow.
"It seems
to regulate normal differentiation of cells as they change from stem cells to
adult cells. And it regulates the growth rate of normal cells and cancer
cells," said study author Dr. Adam Murphy, an assistant professor of
urology at Northwestern University's Feinberg School of Medicine, in Chicago.
Vitamin D is
also known as the "sunshine vitamin" because skin makes it when
exposed to sunlight. Vitamin D levels tend to drop with advancing age, and
deficiency is more common in seasons and regions that get less sunlight and in
people with darker skin, which naturally blocks the sun.
What about the
vitamin's possible relationship to cancer?
"When you
squirt vitamin D on prostate cells in a petri dish, their rate of growth slows
down," Murphy said.
The idea is that
too little of this critical vitamin in the body may cause cell growth to go
awry, leading to cancer.
To test that
idea, researchers checked vitamin D levels in 667 Chicago men between the ages of 40 and 79 who
were having prostate biopsies because they'd recently had an abnormal prostate
specific antigen (PSA) test or because a doctor felt changes to the prostate
during a physical exam.
Normal vitamin D
levels are in the range of 30 to 80 nanograms per milliliter (ng/ml).
Vitamin D
deficiency, or a level under 20 ng/ml, was relatively common among all the men
tested.
About 44 percent
of the men with positive biopsies and 38 percent of those who tested negative
for cancer had low vitamin D levels.
Among men who
tested positive for cancer after their biopsies, those who also had very low
levels of vitamin D -- under 12 ng/ml -- had greater odds of more advanced and
aggressive cancers than those with normal levels.
The connection
between vitamin D and cancer seemed to be even stronger in black men.
Black men with
vitamin D levels under 12 ng/ml were far more likely than those with normal
levels to test positive for prostate cancer in the first place.
In general,
black men are also more likely to be diagnosed with prostate cancer. On
average, men have about a one-in-seven lifetime risk of getting prostate
cancer. That risk rises to one in five for black men, according to the U.S.
Centers for Disease Control and Prevention.
Researchers
aren't sure whether lower vitamin D levels may help to explain why black men
are at higher risk for prostate cancer.
They say longer
and larger studies are needed to sort out the connection.
http://www.webmd.com/prostate-cancer/news/20140501/low-vitamin-d-linked-to-aggressive-advanced-prostate-cancers-study