Vitamin D May Prevent Colorectal Cancer

Vitamin D can stimulate the immune system to protect against a specific type of colorectal cancer, according to a study published online January 15, 2015 in Gut.

Previous trials have suggested that higher vitamin D levels lower the risk of colorectal cancer, as it is clear that vitamin D boosts immune system function by activating T cells to recognize and attack cancer cells. Based on those findings, the authors of the current study believed that the inverse association between vitamin D and colorectal cancer risk might be stronger for cancers with high-level immune response than those with low-level immune response. That is, vitamin D could lower the risk of colorectal cancer with intense immune reaction.

The investigators conducted a nested case—control study of 318 rectal and colon carcinoma cases and 624 matched controls from the Nurses’ Health Study and Health Professionals Follow-Up Study. The original researchers had kept blood samples drawn during the 1990s from all 942 participants whom, at that time, were cancer-free. All samples were screened for vitamin D’s hepatic metabolite, 25-hydroxyvitamin D [25(OH)D].

Participants with elevated 25(OH)D levels had lower-than-average risk of developing colorectal tumors enriched with immune system cells. However, the rates of colorectal cancer with lower-level immune reaction were similar between study arms.

The inverse association of plasma 25(OH)D with colorectal cancer risk appeared to be stronger for tumors infiltrated with high density of CD3+ T cells than those with lower density of CD3+ T cells, but this finding was not significant.

The investigators concluded that vitamin D can interact with the immune system to raise the body’s defenses against certain types of colorectal cancer, but they fell short of identifying specific vitamin D doses. Nevertheless, their study is the first to definitively connect vitamin D and immune response to cancer in a large human population.