In one meta-analysis of epidemiological studies, published in the World Journal of Gastroenterology in 2013, researchers did not find that supplementation with B6 lowered colorectal cancer risk.
When measuring levels of the nutrient in participant’s blood, however, they found that those with higher levels of vitamin B6 had a 30-50 percent reduced risk of colorectal cancer.
The researchers identified other confounding factors, such as higher levels of exercise and intake of other vitamins, which could have protected against colorectal cancer.
Another prospective study, published in the journal of Cancer Epidemiology, Biomarkers and Prevention, found that higher B6 levels had a protective effect on colorectal cancer risk.