In Japan, drinking coffee reduces the risk of colon cancer in women

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.

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　                              JAMA Oncology Published  January 2021 by Kyoto@Takuma H