Abstract
Colorectal cancer has a high incidence and mortality worldwide, with Westernized lifestyles and diet being significant contributing factors. Vitamin D and calcium have been known to reduce the incidence of colorectal cancer by affecting cell differentiation, proliferation, and apoptosis. Despite observational studies which have suggested that a higher serum vitamin D level can lower the risk of colorectal cancer and improve survival rates, no large-scale randomized controlled trials to establish these benefits have been conducted to date. Calcium intake has also been found to have a beneficial role in reducing the incidence and improving survival rates of colorectal cancer in several observational studies. Moreover, intervention studies have proved its effect in preventing colorectal adenomas. However, there are few intervention studies that have identified the relationship of vitamin D and calcium with colon cancer. To elucidate the impact of vitamin D and calcium supplementation on colorectal cancer, well-designed and large-scale randomized controlled trials are necessary in the future.