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Green Tea at a Glance
Green tea comes from Camellia sinensis, the same species used to make black, white, oolong and pu-erh tea. Processing differences, not different plant species, create these major tea styles.
Constituents
Green tea naturally contains caffeine, the amino acid L-theanine and polyphenols such as catechins, including EGCG. Brew strength, leaf quality and preparation influence the amount consumed.
Food and Traditional Use
Tea has been consumed for centuries in East Asia as a daily beverage with social, culinary and cultural importance. Traditional wellness meanings should be distinguished from modern clinical research.
Research
Population studies and clinical trials have examined green tea in relation to cardiovascular and metabolic health. Effects are generally modest and cannot be separated from overall diet and lifestyle. Green tea is not a treatment for cancer, obesity or cardiovascular disease.
Safety
Brewed green tea is generally well tolerated, but caffeine can cause insomnia, anxiety, palpitations or reflux in sensitive people. High-dose concentrated green tea extracts, particularly on an empty stomach, have been associated with liver injury in rare cases. Extract supplements therefore deserve more caution than ordinary brewed tea. Tea can also reduce absorption of non-heme iron when consumed with meals.
Preparation
Water temperature and steep time change flavor and caffeine extraction. People sensitive to caffeine can shorten steeping, reduce leaf amount or choose decaffeinated tea, although decaffeinated tea still contains small residual amounts.
Folklore and Culture
Tea traditions carry deep ceremonial meanings related to hospitality, mindfulness and social connection in many cultures.
Bottom Line
Green tea is best understood as a traditional beverage with a substantial research literature and a safety profile that differs sharply between brewed tea and concentrated extracts. For educational purposes only.