Abstract
BackgroundExperimental studies have revealed that green tea catechins and theanine prevent influenza infection, while the clinical evidence has been inconclusive. This study was conducted to determine whether taking green tea catechins and theanine can clinically prevent influenza infection.MethodsDesign, Setting, and Participants: A randomized, double-blind, placebo-controlled trial of 200 healthcare workers conducted for 5 months from November 9, 2009 to April 8, 2010 in three healthcare facilities for the elderly in Higashimurayama, Japan.Interventions: The catechin/theanine group received capsules including green tea catechins (378 mg/day) and theanine (210 mg/day). The control group received placebo.Main Outcome Measures: The primary outcome was the incidence of clinically defined influenza infection. Secondary outcomes were (1) laboratory-confirmed influenza with viral antigen measured by immunochromatographic assay and (2) the time for which the patient was free from clinically defined influenza infection, i.e., the period between the start of intervention and the first diagnosis of influenza infection, based on clinically defined influenza infection.ResultsEligible healthcare workers (n = 197) were enrolled and randomly assigned to an intervention; 98 were allocated to receive catechin/theanine capsules and 99 to placebo. The incidence of clinically defined influenza infection was significantly lower in the catechin/theanine group (4 participants; 4.1%) compared with the placebo group (13 participants; 13.1%) (adjusted OR, 0.25; 95% CI, 0.07 to 0.76, P = 0.022). The incidence of laboratory-confirmed influenza infection was also lower in the catechin/theanine group (1 participant; 1.0%) than in the placebo group (5 participants; 5.1%), but this difference was not significant (adjusted OR, 0.17; 95% CI, 0.01 to 1.10; P = 0.112). The time for which the patient was free from clinically defined influenza infection was significantly different between the two groups (adjusted HR, 0.27; 95% CI, 0.09 to 0.84; P = 0.023).ConclusionsAmong healthcare workers for the elderly, taking green tea catechins and theanine may be effective prophylaxis for influenza infection.Trial RegistrationClinicalTrials (NCT): NCT01008020
Highlights
Experimental studies have revealed that green tea catechins and theanine prevent influenza infection, while the clinical evidence has been inconclusive
Vaccines are the most widely used intervention for influenza infection prophylaxis, but their effectiveness depends on the type of influenza virus involved in each season’s epidemic, and they have the drawback of limited supply [6]
1 participant in the catechin/ theanine group was excluded according to the exclusion criteria
Summary
Experimental studies have revealed that green tea catechins and theanine prevent influenza infection, while the clinical evidence has been inconclusive. Experimental studies have revealed that green tea catechins can prevent influenza infection in vitro, but clinical evidence has so far been inconclusive [9]. The consumption of tea extracts including catechins and theanine has been reported to enhance systemic immunity and prevent the occurrence of upper respiratory tract infection and influenza symptoms in healthy adults [11]. Based on these findings, we designed a randomized, double-blind study to evaluate the clinical efficacy of green tea catechins and theanine in preventing influenza infection
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