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Researchers
report they have found that vitamin D may provide some protection
against the increased risk of colon cancer associated with
a high fat diet.
Dr. David
J. Mangelsdorf of the University of Texas Southwestern Medical
Center in Dallas, reporting in Science, said the link between
vitamin D and colon cancer appears to be the response of the
vitamin D receptor found in the intestine to levels of lithocholic
acid.
Under
normal conditions, lithocholic acid -- a bile acid produced
when fat breaks down -- is mildly toxic.
When vitamin
D levels are adequate, the vitamin D receptor responds by
producing the cytochrome P450 enzyme, CYP3A, which breaks
down the lithocholic acid.
But vitamin
D levels are low, or when excess fat stimulates an overproduction
of lithocholic acid, the vitamin D receptor's action is overwhelmed
and lithocholic acid builds up to toxic levels, the researchers
said.
Despite
the apparent linkage between vitamin D and colon cancer, the
researchers emphasized that it would be foolhardy for people
to simply take more vitamin D in an effort to offset the increased
risk posed by a high-fat diet, since high doses of vitamin
D can lead to hypercalcemia, a serious metabolic disorder.
Source:
Colorectal
Cancer Week of May 19, 2002
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