What's Actually In Your Cup: The Science of Tea & Health

Tea is sold by the marketing department on a thousand vague promises: detox, immunity, longevity, calm. Most of those claims are either unsupported or wildly overstated. The actual science is more interesting — and more modest — than the wellness shelf would suggest.

**Catechins.** A class of antioxidant polyphenol concentrated in green and white teas. EGCG (epigallocatechin gallate) is the most studied. The evidence: large observational studies in Japan and China consistently associate regular green tea consumption (3–5 cups a day) with modestly lower rates of cardiovascular disease and certain cancers. The evidence is real but correlational. Drinking green tea is not a substitute for not smoking.

**L-theanine.** An amino acid found almost exclusively in tea. Crosses the blood-brain barrier and increases alpha-wave activity, producing a calm, focused mental state. The combination of L-theanine plus caffeine is responsible for tea's distinctive 'alert without jittery' character — different from coffee, where caffeine acts mostly alone. Shade-grown teas (gyokuro, matcha) contain noticeably more L-theanine than sun-grown teas.

**Caffeine.** Yes, all real tea contains caffeine. The popular claim that white tea is 'caffeine-free' is incorrect. Decaffeinated tea is real, but the process strips out a lot of flavour.

**Tannins.** The reason tea makes your mouth feel dry. They bind to iron in your gut, which means drinking tea with iron-rich meals can reduce iron absorption by up to 60%. If you're iron-deficient, drink tea between meals, not with them.

**Things tea does *not* do**, despite what packaging may suggest: 'detox' your liver (your liver detoxes itself, very effectively), 'boost' your immune system in any clinically meaningful way, or burn fat at any rate that would matter. The honest version of tea's health story is: it's a hydrating, mildly stimulating, mildly antioxidant beverage with no calories. That is more than enough.