Vitamin D in colon binds to bile acid, say M. Makishima and colleagues at the University of Texas’s Howard Hughes Institute.

When a person eats fatty foods various bile acids enter the intestine from the liver to absorb the fatty substances. Having done their work, all but one bile acid, lithocholic acid (LCA), returns to the liver. LCA is normally destroyed by the enzyme CYP3A but,If this fails, the LCA passes on to the colon, where it can cause cancer.

The researchers found that vitamin D3 appears to act as a sensor for high LCA levels. When it senses these, vitamin D3 receptor molecules bind to the LCA, triggering a release of CYP3A. If there is insufficient vitamin D3 available, or the person’s diet is too fatty, the process fails, increasing the risk of colon cancer.

Ed.- The researchers hope the new understanding will lead to a less toxic vitamin D3-based treatment but regular exposure of the skin to sunlight would probably provide protection from all but the fattiest diets.

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