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

Matsumoto K, Yamada H, Takuma N, Niino H, Sagesaka YM - BMC Complement Altern Med (2011)

Bottom Line: Experimental studies have revealed that green tea catechins and theanine prevent influenza infection, while the clinical evidence has been inconclusive.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).Among healthcare workers for the elderly, taking green tea catechins and theanine may be effective prophylaxis for influenza infection.

View Article: PubMed Central - HTML - PubMed

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

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.

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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Related in: MedlinePlus

Kaplan-Meier curves of clinically defined influenza.
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Figure 2: Kaplan-Meier curves of clinically defined influenza.

Mentions: Kaplan-Meier curves were shown in Figure 2. The time for which the patient was free from clinically defined influenza infection, estimated with the Cox proportional hazards regression model, was significantly different between the two groups (adjusted hazard ratio, 0.27; 95% CI, 0.09 to 0.84; P = 0.023) (Table 2). No serious adverse events were observed during the study. Digestive symptoms such as bloating and constipation occurred in both groups and were reported by 9.2% of all participants. These symptoms were relativity mild and did not significantly differ between the two groups.


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

Matsumoto K, Yamada H, Takuma N, Niino H, Sagesaka YM - BMC Complement Altern Med (2011)

Kaplan-Meier curves of clinically defined influenza.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3049752&req=5

Figure 2: Kaplan-Meier curves of clinically defined influenza.
Mentions: Kaplan-Meier curves were shown in Figure 2. The time for which the patient was free from clinically defined influenza infection, estimated with the Cox proportional hazards regression model, was significantly different between the two groups (adjusted hazard ratio, 0.27; 95% CI, 0.09 to 0.84; P = 0.023) (Table 2). No serious adverse events were observed during the study. Digestive symptoms such as bloating and constipation occurred in both groups and were reported by 9.2% of all participants. These symptoms were relativity mild and did not significantly differ between the two groups.

Bottom Line: Experimental studies have revealed that green tea catechins and theanine prevent influenza infection, while the clinical evidence has been inconclusive.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).Among healthcare workers for the elderly, taking green tea catechins and theanine may be effective prophylaxis for influenza infection.

View Article: PubMed Central - HTML - PubMed

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

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.

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.

Show MeSH
Related in: MedlinePlus