New research suggests that vitamin D may protect against colon cancer by helping to get rid of a toxic acid that promotes the disease. The discovery could point the way to the development of therapies that provide the cancer protection of vitamin D without the side effects caused by consuming too much of the vitamin.
A new report from researchers at the University of Texas Southwestern Medical Center in Dallas provides a possible explanation for the protection of vitamin D as well as the increased risk of a high-fat diet.
When a person eats fatty foods, the liver empties bile acids into the intestine, making it possible for the body to digest and absorb fatty substances. After doing their job in the intestine, most bile acids are taken back into the liver. But one bile acid, called LCA, does something unusual. It is not recirculated into the liver. Instead, an enzyme called CYP3A degrades LCA in the intestine. If the bile acid LCA is not detoxified by the enzyme, it passes into the colon where it can promote cancer.
Since vitamin D has been shown to prevent colon cancer in animals, the researchers decided to see whether its receptor had any effect on the detoxification of LCA. In fact, the vitamin D receptor seems to act as a sensor for high levels of LCA. The vitamin D receptor binds to LCA, triggering an increase in the bile acid-neutralizing enzyme. This seems to be the body's way of protecting itself from colon cancer.
If a person does not get enough vitamin D, this balance may be interrupted, increasing the risk of colon cancer.
The research also provides a possible explanation of how high-fat diets may increase the risk of colon cancer. Since LCA is released from the liver when a person eats fatty food, a high-fat diet that keeps LCA levels high may overwhelm the body.
The researchers stated that a high-fat diet is "something our bodies were never, never meant to have to deal with."
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