Higher levels of vitamin D linked to lower colorectal cancer risk in women

CANCER DIGEST – June 15, 2018 – People with higher levels of vitamin D in their blood appear to have protection against colorectal cancer, according to a new study in the Journal of the National Cancer Institute.

Vitamin D plays a key role in maintaining bone health, but research has produced clues that it may also lower the risk of colorectal cancer due to effects on cell growth and regulation, however the studies aimed to evaluate a protective effect have been inconsistent.

The current study was designed to address the inconsistencies by using single, widely accepted test to measure vitamin D levels across more than 20 medical centers. It involved 5,706 people with colorectal cancer and 7107 participants without cancer.  Results showed that higher levels of vitamin D than previously thought to be optimal may be the key to protecting against colorectal cancer, in women, but may not have the same effect in men.

The study showed that compared to participants with blood levels of vitamin D considered sufficient for bone health, people who did not have enough vitamin D had a 31 percent higher risk of colorectal cancer during the average 5.5 years of follow-up. In addition, they found that people with higher concentrations of the vitamin than considered sufficient for bone health had 22 percent lower risk of colorectal cancer, but the risk did not continue to go down at the highest levels of vitamin D.

Interestingly, the researchers noted that the lower risk of colorectal cancer was stronger in women than men in those with vitamin D levels above that needed for bone health.

"Currently, health agencies do not recommend vitamin D for the prevention of colorectal cancer," said Marji L. McCullough, ScD, in a press release. She is an American Cancer Society epidemiologist and co-first author of the study. "This study adds new information that agencies can use when reviewing evidence for vitamin D guidance and suggests that the concentrations recommended for bone health may be lower than would be optimal for colorectal cancer prevention."

Vitamin D can be obtained in the diet from fortified foods and supplements and sun exposure, but experts recommend dietary intake to avoid the ultraviolet radiation risk of skin cancer from excessive sun exposure. High fat fish such as salmon, trout, sword fish, and tuna, eggs and mushrooms all contain small amounts of vitamin D.

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