Relationship between coffee drinking, vitamin D intake, aspirin taking and colorectal cancer risk in Japan

In recent years, the incidence of colorectal cancer has increased rapidly in Japan. In 2018, Japan's Ministry of Health, Labor and Welfare reported that among all cancer types, colorectal cancer deaths ranked third for men and first for women. Coffee, which is consumed worldwide, has been reported to have a preventive effect on the pathological conditions associated with the development of colorectal cancer by suppressing bile acids in the intestine, which has a carcinogenic promoting effect.
The relationship between coffee drinking and colorectal cancer is drawing attention. However, the results of a meta-analysis summarizing the research results of coffee drinking and colorectal cancer are inconsistent.

Coffee drinking is associated with a reduced risk of colon cancer in women
In 2019, the Japan Society of Cancer analyzed the association between drinking coffee and cancers in each part of the large intestine (colon cancer, rectum cancer, proximal colon cancer, distal colon cancer) (1). As a result, in the men, no clear association was found between the development of cancer in each part of the large intestine and drinking coffee. In the women, by analyzing cancer in each part of the large intestine, a 20% lower risk of colon cancer was observed in the group who drank three or more cups of coffee a day compared to the group who drank less than one cup of coffee a day.

This study found no association between coffee drinking and overall colorectal cancer risk for both men and women. However, analysis of cancer in each part of the large intestine revealed that drinking coffee in women reduced the risk of developing colon cancer. As a mechanism for preventing colon cancer by drinking coffee, it is considered that drinking coffee suppresses intestinal bile acids, which have a carcinogenic promoting effect, inflammation related to colorectal cancer risk, insulin resistance, and insulin secretion. As another mechanism, it is considered that drinking coffee activates the movement of the large intestine.

In Japan, the results of studies on the association between taking supplements such as vitamins and the development of colorectal cancer differ depending on the cohort of clinical studies and study design. Compared to other groups, the risk of rectal cancer has been shown to be higher in the group with the lowest levels of vitamin D in both men and women. Recently, it has been pointed out that excessive intake of vitamin D may exacerbate serrated polyposis syndrome (SPS) syndrome. Many clinical studies report that taking aspirin reduces the risk of developing colorectal cancer.

Disclosure of potential conflicts of interest
The authors declare no potential conflicts of interest.

Acknowledgments
We thank all the medical staffs and co-medical staffs for providing and helping medical research at National Hospital Organization Kyoto Medical Center. We appreciate Crimson Interactive Japan Co., Ltd. for revising and polishing our manuscript by Native English.

Reference
1. https://epi.ncc.go.jp/en/can_prev/evaluation/index.html

がん医療専門ドクター/癌ゲノム医療/新興感染症　                                  JAMA Oncology Published on March 20. 2021. by Kyoto@Takuma H