The research, published in the journal Gut, investigated whether there is an inverse association between vitamin D status and cancers with high-level immune response than those with low-level immune response using colorectal cancer risk as a model.
Led by researchers from the Dana-Farber Cancer Institute at Harvard Medical School, the team noted that previous evidence has suggested protective effects of vitamin D and anti-tumour immunity on colorectal cancer risk – adding that it is also known that immune cells in some tumour environments can convert 25-hydroxyvitamin D [25(OH)D] to bioactive 1α,25-dihydroxyvitamin D3, which then primes an immune response.
"Laboratory research suggests that vitamin D boosts immune system function by activating T cells that recognise and attack cancer cells,” explained senior author Dr Shuji Ogino.
“In this study, we wanted to determine if these two phenomena are related: Does vitamin D's role in the immune system account for the lower rates of colorectal cancer in people with high circulating levels of the vitamin?"
Using data from the Nurses’ Health Study and Health Professionals Follow-up Study the team performed a nested case–control study, which found that people with high levels of vitamin D in their bloodstream have a lower overall risk of developing colorectal cancer.
“High plasma 25(OH)D level is associated with lower risk of colorectal cancer with intense immune reaction, supporting a role of vitamin D in cancer immunoprevention through tumour–host interaction,” reported Ogino and his colleagues - adding that their research is the first time that a link between vitamin D and the immune response to cancer has been shown in a large human population.
The team used data from 170,000 participants in the Nurses' Health Study and Health Professionals Follow-up Study, to compare carefully selected groups of 318 colorectal cancer patients and 624 individuals who were free of cancer in a nested case–control study.
All 942 participants had blood samples drawn in the 1990s, before any developed cancer. The authors then tested these samples for 25(OH)D) status - finding that those with high amounts of 25(OH)D had a lower-than-average risk of developing colorectal tumours that were enriched with immune system cells.
"This is the first study to show evidence of the effect of vitamin D on anti-cancer immune function in actual patients, and vindicates basic laboratory discoveries that vitamin D can interact with the immune system to raise the body's defences against cancer," said Ogino.
"In the future, we may be able to predict how increasing an individual's vitamin D intake and immune function can reduce his or her risk of colorectal cancer,” he said.
Published online ahead of print, doi: 10.1136/gutjnl-2014-308852
“Plasma 25-hydroxyvitamin D and colorectal cancer risk according to tumour immunity status”
Authors: Mingyang Song, Reiko Nishihara, et al