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Effects of green tea catechins and theanine on preventing influenza infection among healthcare workers: a randomized controlled trial.

Abstract

BACKGROUND

Experimental 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.

METHODS

DESIGN, 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.

RESULTS

Eligible 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).

CONCLUSIONS

Among healthcare workers for the elderly, taking green tea catechins and theanine may be effective prophylaxis for influenza infection.

TRIAL REGISTRATION

ClinicalTrials (NCT): NCT01008020.

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  • Authors+Show Affiliations

    ,

    Department of Drug Evaluation & Informatics, Graduate School of Pharmaceutical Sciences, University of Shizuoka, Yada, Suruga-ku, Shizuoka, Japan.

    , , ,

    Source

    MeSH

    Adult
    Camellia sinensis
    Catechin
    Double-Blind Method
    Glutamates
    Health Personnel
    Humans
    Incidence
    Influenza, Human
    Phytotherapy
    Plant Extracts
    Tea

    Pub Type(s)

    Journal Article
    Randomized Controlled Trial
    Research Support, Non-U.S. Gov't

    Language

    eng

    PubMed ID

    21338496

    Citation

    TY - JOUR T1 - Effects of green tea catechins and theanine on preventing influenza infection among healthcare workers: a randomized controlled trial. AU - Matsumoto,Keiji, AU - Yamada,Hiroshi, AU - Takuma,Norikata, AU - Niino,Hitoshi, AU - Sagesaka,Yuko M, Y1 - 2011/02/21/ PY - 2010/10/13/received PY - 2011/02/21/accepted PY - 2011/2/23/entrez PY - 2011/2/23/pubmed PY - 2011/7/27/medline SP - 15 EP - 15 JF - BMC complementary and alternative medicine JO - BMC Complement Altern Med VL - 11 N2 - BACKGROUND: Experimental 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. METHODS: DESIGN, 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. RESULTS: Eligible 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). CONCLUSIONS: Among healthcare workers for the elderly, taking green tea catechins and theanine may be effective prophylaxis for influenza infection. TRIAL REGISTRATION: ClinicalTrials (NCT): NCT01008020. SN - 1472-6882 UR - https://www.unboundmedicine.com/medline/citation/21338496/full_citation L2 - https://bmccomplementalternmed.biomedcentral.com/articles/10.1186/1472-6882-11-15 ER -