2022 Fiscal Year Final Research Report

The effects of green tea gargling on preventing influenza infection: A randomized clinical study focused on the catechin concentrations

Research Project

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Project/Area Number	20K10382
Research Category	Grant-in-Aid for Scientific Research (C)
Allocation Type	Multi-year Fund
Section	一般
Review Section	Basic Section 58010:Medical management and medical sociology-related
Research Institution	University of Shizuoka
Principal Investigator	Yamada Hiroshi 静岡県立大学, 薬学部, 特任教授 (40265252)
Co-Investigator(Kenkyū-buntansha)	古島大資静岡県立大学, 薬学部, 講師 (90615238)
Project Period (FY)	2020-04-01 – 2023-03-31
Keywords	green tea / catechin / gargling / influenza / randomization / concentration dependence
Outline of Final Research Achievements	Catechins, the major components of green tea, exhibit antiviral activities in experimental studies. We investigated the clinical effects of concentration-dependence of green tea catechins in gargling on the influenza infection. We conducted a randomized clinical study and the target population consisted of 209 university students, who were randomly assigned to high-catechin contained green tea (high-catechin group), low-catechin contained green tea (low-catechin group), or water (control group). All participants gargled thrice daily for 12 weeks in the coronavirus disease 2019 (COVID-19) pandemic from December 2021. The results showed no influenza infection occurred. The upper respiratory tract infections occurred in 9.1%, 10.8%, and 15.7% participants in the high-catechin, low-catechin, and control group. Our findings revealed a concentration-dependent decrease in the incidence of upper respiratory tract infections; however, a statistically significant difference was not observed.
Free Research Field	公衆衛生学
Academic Significance and Societal Importance of the Research Achievements	本研究は、緑茶の主要成分であるカテキンが基礎研究において抗インフルエンザウイルス作用を示しながら、ヒトにおけるエビデンスが十分に定まっていない点に着目し、濃度依存性の観点から緑茶うがいの臨床的な予防効果を追求した点に学問的意義がある。また、インフルエンザの予防対策が公衆衛生的に種々行われながら完全に感染を阻止し得ない現状の中で、緑茶うがいという簡便、且つ安全、安価な方法がインフルエンザ予防対策の補助手段となり得るかを検討した点に社会的意義がある。