Contents
What it is
Green tea is made from tea leaves that are never allowed to oxidise. It comes from the same leaf as black, oolong and white tea; only the handling differs. The key step is to halt the oxidising enzymes right after picking, by pan-firing or steaming, which is what keeps the leaf green and leaves the astringent catechins intact. Korea and China mostly pan-fire while Japan mostly steams, and the aromas differ accordingly. Water that is too hot pulls out astringency and bitterness, which is why 70–80°C is so often recommended.
Scientific name Camellia sinensis
Green and black tea come from the same leaf. The difference is oxidation. Green tea leaves are heated right after picking, which stops the oxidising enzymes and leaves the catechins — especially EGCG — intact.
Add to that L-theanine, an amino acid that is unusually abundant in green tea. Caffeine's alertness plus theanine's calm is why people describe green tea as a different kind of focus from coffee.
Key benefits
- Moderate evidence
It nudges LDL cholesterol and blood pressure down
Across 14 randomised trials (1,136 people), total cholesterol fell 7.2 mg/dL and LDL 2.2 mg/dL. A separate meta-analysis found systolic pressure down 2.1 mmHg and diastolic down 1.7 mmHg. These are all small numbers — an LDL drop of 2.2 mg/dL is not something you would feel. Notably, the cholesterol analysis found the same result regardless of catechin dose or how long people drank it.[1][2]
- Moderate evidence
It produces focus and calm at the same time
L-theanine increases alpha wave activity in the brain, a state of relaxed alertness. Taken together with caffeine, it outperformed caffeine alone on attention tasks in trials. That is the source of green tea's steadier, less jittery lift.[3]
- Moderate evidence
It slightly increases fat oxidation
The EGCG-plus-caffeine combination modestly raises daily energy expenditure and fat oxidation. Over weeks, though, the weight-loss effect is small. Green tea supports a diet; it is not a method of losing weight.[4]
- Early research
Oral health rests on observational data
That catechins suppress decay-causing bacteria comes from lab studies, and most of the human trials used tea as a mouthwash rather than a drink. For tea actually drunk, a survey of 16,726 Korean adults found lower periodontal disease among those drinking it two to six times a week — but the same study flagged excessive consumption as a risk factor. This holds for tea drunk without sugar.[5][6]
How to eat it well
- Brew at 70–80°C. Boiling water pulls out too much bitterness from catechins and caffeine, and less of the savoury notes.
- Steep the first cup for one to two minutes. Longer gets astringent. The same leaves are good for two or three infusions.
- Three to five cups a day is the range most often used in research.
- Avoid strong tea right after a meal. Tannins interfere with the absorption of non-heme iron; between meals is better.
- Matcha means consuming the whole leaf, so both catechins and caffeine come in higher.
How to read the grades
Each benefit carries a label showing how far research on people supports it. Grades differ between items even within the same ingredient.
- Nutrition data
- A fact verifiable from food composition databases or health authorities. This is a different kind of statement from a clinical effect.
- Strong evidence
- Consistently confirmed across randomised controlled trials or meta-analyses.
- Moderate evidence
- Human studies exist, but effect sizes are small or results are mixed.
- Early research
- Cell or animal work, or small preliminary studies.
- Not established
- Commonly claimed, but not confirmed in studies on people.
What to watch out for
- A cup contains 20–45 mg of caffeine. If you are caffeine-sensitive or sleep poorly, skip it late in the day.
- Strong tea on an empty stomach can cause heartburn.
- With iron-deficiency anaemia, leave at least an hour between tea and meals.
- Concentrated green tea extract supplements have been linked to rare cases of liver injury. That risk is not the same as drinking the tea.
- In pregnancy, count cups against a total caffeine limit of about 200 mg a day.
Nutrition
Approximate values for one brewed cup (about 240 ml).
Percentages are of the US FDA Daily Value for adults and children 4 and over. National reference intakes differ by sex and age.
Calculate this alongside other ingredients →
Key nutrients
By health concern
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Sources
The databases and health authorities this article's nutrition figures and health statements draw on.
- 1Green tea intake lowers fasting serum total and LDL cholesterol in adults: a meta-analysis of 14 randomized controlled trialsMeta-analysisZheng XX, et al. Am J Clin Nutr 2011PMID 21715508
- 2Green tea catechins and blood pressure: a systematic review and meta-analysis of randomised controlled trialsMeta-analysisKhalesi S, et al. Eur J Nutr 2014PMID 24861099
- 3Acute effects of tea constituents L-theanine, caffeine, and epigallocatechin gallate on cognitive function and mood: a systematic review and meta-analysisSystematic reviewsCamfield DA, et al. Nutr Rev 2014PMID 24946991
- 4The effects of catechin rich teas and caffeine on energy expenditure and fat oxidation: a meta-analysisMeta-analysisHursel R, et al. Obes Rev 2011PMID 21366839
- 5Beverages Consumption and Oral Health in the Aging Population: A Systematic ReviewSystematic reviewsZupo R, et al. Front Nutr 2021PMID 34778347
- 6Excessive Consumption of Green Tea as a Risk Factor for Periodontal Disease among Korean AdultsResearch literatureHan K, et al. Nutrients 2016PMID 27384581
- 7USDA FoodData CentralFood composition database
- 8NIH Office of Dietary SupplementsHealth authority
- 9Cochrane LibrarySystematic reviews
- 10PubMedResearch literature
