What question did this study set out to answer?

To evaluate the immunomodulatory and anti-inflammatory effects of green tea on human immune function.

July 31, 2026Applied Sciences0 citationsOpen Access

Green Tea (Camellia sinensis) Consumption and Human Immune Function: A Systematic Review of Immunomodulatory and Anti-Inflammatory Effects

DDDo Tung Dac NQNguyen Van Quan TXTran Dang Xuan

Key Points

To evaluate the immunomodulatory and anti-inflammatory effects of green tea on human immune function.
Conducted a systematic review in accordance with PRISMA guidelines.
Included 19 studies (≈6800 participants), comprising 12 randomized controlled trials, 3 non-randomized interventional studies, and 5 observational analyses.
Searched PubMed, Google Scholar, Cochrane Library, and EBSCO for relevant human investigations.
Eight studies reported enhanced immune activity, with increased natural killer cell function and γδ T cell responses.
Several trials demonstrated reductions in C-reactive protein in high-risk populations, while others showed no significant changes in interleukin-6 or tumor necrosis factor-α.
Observational studies indicated inverse associations between tea consumption and inflammation.

Abstract

Background: Green tea (Camellia sinensis) is widely consumed around the world, particularly in East Asia, and has traditionally been used to support cardiovascular and metabolic health. Rich in catechins—most notably epigallocatechin-3-gallate (EGCG)—green tea is recognized for its potential immunomodulatory and anti-inflammatory effects. However, evidence from human studies remains inconsistent, and the distinction between functional immune outcomes and systemic inflammatory markers has not been systematically evaluated. Methods: We conducted a systematic review in accordance with PRISMA guidelines, searching PubMed, Google Scholar, Cochrane Library, and EBSCO from inception to the most recent date. Eligible studies included human investigations evaluating green tea or catechin intake and reporting either immune response outcomes (e.g., natural killer cell activity, T cell responses) or systemic inflammatory markers (e.g., C-reactive protein, cytokines). Randomized controlled trials (RCTs), non-randomized interventional studies, and observational analyses were included. Data were synthesized narratively due to heterogeneity. Results: Nineteen studies (≈6800 participants) were included, comprising 12 RCTs, three non-randomized interventions, and five observational studies. Eight studies assessed immune responses and consistently demonstrated enhanced immune activity, including increased natural killer cell function and augmented γδ T cell responses. Eleven studies evaluated inflammatory markers and showed heterogeneous results: several trials reported reductions in C-reactive protein and related biomarkers, particularly in high-risk populations, whereas others found no significant changes in cytokines such as interleukin-6 or tumor necrosis factor-α. Observational studies generally reported inverse associations between tea consumption and inflammation. Green tea was well tolerated across studies. Conclusions: Green tea consumption appears to enhance functional immune responses while exerting modest, context-dependent anti-inflammatory effects. These findings support a dual immunomodulatory role and highlight the importance of distinguishing between immune function and systemic inflammation in nutritional research.

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