Health benefits of different types of tea: a review

Abstract Tea is the most popular beverage consumed next to water worldwide. Various types of tea, including green, black, dark, white, and oolong, are produced from the young, harvestable shoots of the tea plant, with each type undergoing a distinct manufacturing process. Tea is rich in bioactive constituents, including L-theanine, methylxanthines (caffeine, theophylline, and theobromine), polyphenols, γ-aminobutyric acid (GABA), saponins, polysaccharides, etc. Several studies indicate that tea and its phytochemicals exert diverse health-promoting effects. Its antioxidant activity, primarily attributed to polyphenolic compounds, has been associated with a reduced risk of non-communicable diseases, including cardiovascular disorders, certain cancers, neurodegenerative conditions, infectious diseases, and metabolic abnormalities. Tea also demonstrates immunomodulatory and anti-inflammatory effects and can modulate gut microbiota composition, functioning as a prebiotic. These biological activities have been observed in teas across both in vitro and in vivo studies. Additionally, tea consumption has been linked to psychological benefits, such as stress reduction and enhanced cognitive function. Although numerous studies have investigated the health-promoting properties of individual tea types, a comprehensive and systematically structured synthesis comparing green, black, dark, white, and oolong teas based on recent evidence remains limited. This systematic review provides a synthesis of peer-reviewed studies published between 2019 and 2025, focusing on the biological activities and therapeutic potential of major tea varieties and their bioactive compounds.