A study found that vitamin D boosts the immune system's defenses against tumor cells.
"People with high levels of vitamin D in their bloodstream have a lower overall risk of developing colorectal cancer," says lead researcher Shuji Ogino, MD, PhD, from Harvard School of Public Health. "Laboratory research suggests that vitamin D boosts immune system function by activating T [immune] cells that recognize and attack cancer cells."
Long-Term Health Studies
To try to prove the link between vitamin D, the immune system, and bowel cancer rates, Ogino and colleagues drew on data from 942 people enrolled in two long-term health projects. Of these, 318 had colorectal cancer and 624 did not.
All the participants had given blood samples during the 1990s, before any of them had gotten cancer. The investigators tested these samples for 25-hydroxy vitamin D, an accurate measure of how much vitamin D is in your body.
Immune System Cells
They found that people with high amounts of 25-hydroxy vitamin D had a lower risk of getting colorectal tumors that have a large number of immune cells. The authors say this suggests there’s an interaction between vitamin D and the immune system that may work to prevent colorectal cancer.
"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," Ogino says.
Excluding skin cancers, colorectal cancer is the third most common cancer in both men and women in the U.S., according to the American Cancer Society.
Lifestyle and Diet
Mark Flannagan, the chief executive of the U.K. charity Beating Bowel Cancer, comments in a statement: "It’s an interesting study but further research is needed into the role vitamin D plays in bowel cancer survival.
"However, we do know people can take steps to reduce their risk of developing bowel cancer by making simple changes to their lifestyle and diet."
He says those steps should include:
- Get regular exercise.
- If you smoke, quit.
- Have less red meat, processed meat, high-fat foods, and alcohol.