Sumio Hayakawa 1,*, Tomokazu Ohishi 2 , Noriyuki Miyoshi 3 , Yumiko Oishi 1 , Yoriyuki Nakamura 3 and Mamoru Isemura 3,*
1 Department of Biochemistry and Molecular Biology, Graduate School of Medicine, Nippon Medical School, Bunkyo-ku, Tokyo 113-8602, Japan; y-oishi@nms.ac.jp
2 Institute of Microbial Chemistry (BIKAKEN), Numazu, Microbial Chemistry Research Foundation, Shizuoka 410-0301, Japan; ohishit@bikaken.or.jp
3 School of Nutritional and Environmental Sciences, University of Shizuoka, Suruga-ku, Shizuoka 422-8526, Japan; miyoshin@u-shizuoka-ken.ac.jp (N.M.); yori.naka222@u-shizuoka-ken.ac.jp (Y.N.)
* Correspondence: hayakawa_sci@icloud.com (S.H.); isemura@u-shizuoka-ken.ac.jp (M.I.); Tel.: +81-3-3822-2131 (S.H.); +81-54-264-5920 (M.I.)
Received: 20 August 2020; Accepted: 28 September 2020; Published: 5 October 2020
Abstract: Tea and coffee are consumed worldwide and epidemiological and clinical studies have shown their health beneficial effects, including anti-cancer effects. Epigallocatechin gallate (EGCG) and chlorogenic acid (CGA) are the major components of green tea polyphenols and coffee polyphenols, respectively, and believed to be responsible for most of these effects. Although a large number of cell-based and animal experiments have provided convincing evidence to support the anti-cancer effects of green tea, coffee, EGCG, and CGA, human studies are still controversial and some studies have suggested even an increased risk for certain types of cancers such as esophageal and gynecological cancers with green tea consumption and bladder and lung cancers with coffee consumption. The reason for these inconsistent results may have been arisen from various confounding factors. Cell-based and animal studies have proposed several mechanisms whereby EGCG and CGA exert their anti-cancer effects. These components appear to share the common mechanisms, among which one related to reactive oxygen species is perhaps the most attractive. Meanwhile, EGCG and CGA have also different target molecules which might explain the site-specific differences of anti-cancer effects found in human studies. Further studies will be necessary to clarify what is the mechanism to cause such differences between green tea and coffee.
Keywords: cancer; tea; coffee; EGCG; chlorogenic acid; ROS; AMPK; NF-κB
