The connection between deficiency of vitamin D and the risk of colorectal cancer has been established and there is evidence for a connection between vitamin D status and other cancers of the digestive system. High-risk groups include people with low vitamin D intake, those who live where sunlight intensity is low, those who use sunscreen thoroughly, those who have darker skin and those who live in nursing homes.
A daily dose of 200-400 IU/day may not be sufficient to prevent these cancers. Vitamin D status at the time of diagnosis of colorectal cancers influences the outcome of the cancer. Higher levels of calcium and vitamin D are associated with improved rates of apoptosis of abnormal cells in colorectal tissues. Apoptosis is a natural form of cell death caused by the immune system.
CONCLUSION: Vitamin D status influences the risk of colorectal cancer and other digestive tract cancers. Higher blood levels of vitamin D and exposure to sunshine seem to improve the outcome of treatment of colorectal cancers. Further studies must be done.
Studies have used up to 3,000 IU/day of vitamin D. The higher doses have been associated with higher rates of apoptosis.
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