Does green tea help against infections?

Flu prevention is the area where green tea has the strongest supporting evidence. A meta-analysis of five small randomised studies (884 participants) and three cohort studies (2223 participants) found that catechins from green tea reduce the likelihood of flu by approximately 38% (combined risk: 0.62). That effect occurred with both gargling and simply drinking tea. The studies are small and the doses varied, which means larger follow-up studies are needed to confirm the finding.

With bacterial infections the picture is very different. Laboratory research shows that catechins can target bacteria in several ways: they damage the cell wall, inhibit certain bacterial enzymes and cause oxidative stress. The strongest activity is found in the compounds EGCG and ECG. However, this has been demonstrated almost exclusively outside the body. Whether you get the same effects by simply drinking green tea has not been established.

For HPV-related conditions, such as cervical lesions and external genital warts, results from randomised trials point to a beneficial effect of catechin treatment. The exact dosage and effect size are not worked out in the available information, so concrete practical recommendations cannot yet be given here.

The antioxidant and anti-inflammatory properties of green tea are regularly cited as a possible explanation for protection against infections. That is biologically plausible, but direct clinical evidence for infection prevention via this pathway is still lacking. It remains a hypothesis that deserves further research.