Vitamin D, specifically its receptor, slows the action of a key protein in the carcinogenic process of colon cancer cells, researchers in Spain say.Researchers at the Vall d\'Hebron Institute of Oncology in Barcelona, Spain, and colleagues say the protein, known as beta-catenin, is normally found in intestinal epithelial cells where cancer tumor transformation begins.The protein is retained in the cell nucleus, where it facilitates the carcinogenic process, and this is the point the vitamin D receptor intervenes \"Our study has confirmed the pivotal role of the vitamin D receptor in controlling the anomalous signal that sparks off the growth and uncontrolled proliferation of colon cells which, in the final instance, ends up causing a tumor to emerge,\" Hector Palmer, the coordinator of the study, says in a statement.In light of these findings, chronic vitamin D deficiency represents a risk factor in the development of more aggressive colon tumors, Palmer says.The study, published in the journal PLoS One, says patients in the initial stages of colon cancer, when the vitamin D receptor still has a substantial presence in the cells, could benefit from vitamin D3, but this would not be useful in the advanced stages when the presence of the vitamin D receptor is very much reduced.