Camellia sinensis
Camellia sinensis is the plant behind all true teas (green, black, oolong, white, pu-erh). Brewed tea is one of the better-studied beverages for cardiovascular health — Cochrane evidence shows green tea modestly lowers blood pressure and LDL cholesterol. Cancer-prevention evidence is mixed at best (2020 Cochrane: inconsistent). High-dose green tea extracts (≥800 mg EGCG/day) carry a real hepatotoxicity signal and have triggered USP/EFSA warnings — brewed tea is far safer than concentrated capsules.
Quick decision guide
May help most
Adults who want a low-calorie, well-studied beverage for cardiovascular and metabolic health. Brewed green or black tea, 2–5 cups/day, is the evidence-based pattern.
Common dosing range
Brewed tea: 2–5 cups/day (~200–500 mg total catechins from green tea). If choosing extracts, keep EGCG <800 mg/day and avoid taking on an empty stomach.
When to expect effects
Weeks for BP and lipid changes; days for caffeine-mediated alertness and acute metabolic effects.
Watch out for
Concentrated green tea extracts (EGCG ≥800 mg/day) can cause severe acute liver injury. Brewed tea is far safer. Tannins reduce non-heme iron absorption — drink between meals if you're iron-deficient.
Evidence snapshot
What is it
Camellia sinensis is the tea plant. All true teas (green, black, oolong, white, pu-erh) come from its leaves; differences are due to processing. Supplements typically use standardized green tea leaf extracts.
Is it worth it for you?
Use this as a quick fit check, not a diagnosis.
Worth considering if…
Probably skip if…
Evidence at a glance
| Goal | Effect | Best fit | Time |
|---|---|---|---|
Blood pressure Good Evidence | −3.2 mmHg systolic, −3.4 mmHg diastolic (green tea, 11-trial pooled estimate) | Adults with high-normal or stage 1 hypertension wanting a low-risk dietary lever | 3–6 months in trials |
LDL cholesterol and lipids Good Evidence | LDL −0.64 mmol/L (~25 mg/dL), total cholesterol −0.62 mmol/L vs control | Adults with borderline-elevated cholesterol or strong family history of CV disease wanting a dietary lever | 3–6 months |
Modest weight loss (green tea catechins + caffeine) Limited Evidence | ~0.5–1.5 kg additional weight loss over 12–24 weeks with GTC + caffeine vs control | Caffeine-naive adults using catechin-containing tea or extract alongside diet and exercise | 8–24 weeks |
Cancer prevention Limited Evidence | No clear preventive effect across most cancer sites; possible signal for prostate cancer (not significant) | Anyone replacing sugary drinks with tea — the swap itself has plausible benefits beyond direct catechin effects | Decades for cancer endpoints |
Blood pressure
- Effect
- −3.2 mmHg systolic, −3.4 mmHg diastolic (green tea, 11-trial pooled estimate)
- Best fit
- Adults with high-normal or stage 1 hypertension wanting a low-risk dietary lever
- Time
- 3–6 months in trials
LDL cholesterol and lipids
- Effect
- LDL −0.64 mmol/L (~25 mg/dL), total cholesterol −0.62 mmol/L vs control
- Best fit
- Adults with borderline-elevated cholesterol or strong family history of CV disease wanting a dietary lever
- Time
- 3–6 months
Modest weight loss (green tea catechins + caffeine)
- Effect
- ~0.5–1.5 kg additional weight loss over 12–24 weeks with GTC + caffeine vs control
- Best fit
- Caffeine-naive adults using catechin-containing tea or extract alongside diet and exercise
- Time
- 8–24 weeks
Cancer prevention
- Effect
- No clear preventive effect across most cancer sites; possible signal for prostate cancer (not significant)
- Best fit
- Anyone replacing sugary drinks with tea — the swap itself has plausible benefits beyond direct catechin effects
- Time
- Decades for cancer endpoints
Evidence for 4 uses
AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.
Blood pressure
Supplement benefitThe 2013 Cochrane primary-prevention review (Hartley et al., 11 RCTs, n=821) found green tea reduced systolic BP by ~3 mmHg and diastolic BP by ~3 mmHg over 3–6 months; black tea showed smaller reductions (~2 mmHg). The effect size is meaningful at the population level but modest for any individual. Subsequent meta-analyses are consistent. Brewed tea, not concentrated extract, is the form with the strongest evidence.
Bottom line: A small but real BP reduction with daily brewed tea. Stack on top of (not replace) prescribed treatment.
LDL cholesterol and lipids
Supplement benefitThe Hartley 2013 Cochrane review found green tea reduced LDL by ~0.64 mmol/L (~25 mg/dL) and total cholesterol by ~0.62 mmol/L over 3–6 months. Black tea showed smaller, less consistent effects. Triglycerides and HDL were largely unaffected. The mechanism is attributed to catechins (notably EGCG) reducing cholesterol absorption and modulating hepatic LDL receptor expression.
Bottom line: A clinically meaningful LDL reduction from brewed tea over months. Worth adding; not a statin replacement.
Modest weight loss (green tea catechins + caffeine)
Supplement benefitMultiple meta-analyses of GTC+caffeine over 8–24 weeks find ~0.5–1.5 kg additional weight loss vs control, mostly when caffeine is present. The effect is small, plateaus after a few months, and is more reliable in caffeine-naive participants. Most trials used green tea extracts at 300–600 mg catechins/day; the brewed-tea-only signal is smaller.
Bottom line: Small bonus when added to a real weight-loss plan; don't expect tea to do the heavy lifting.
Cancer prevention
Supplement benefitThe 2020 Cochrane review (Filippini et al., 142 studies including 11 RCTs and 131 observational) found inconsistent evidence overall. A possible reduction in prostate cancer incidence in the green tea–supplemented arm (RR 0.50, 95% CI 0.18–1.36, 3 studies) didn't reach statistical significance. Authors concluded the evidence base is dominated by Asian observational studies with risk of confounding by overall dietary pattern.
Bottom line: Don't take green tea pills for cancer prevention. Drink tea if you enjoy it; rely on screening and lifestyle for actual prevention.
Evidence is mixed
Asian cohort studies suggest reduced gastric, esophageal, and lung cancer risk among heavy tea drinkers; RCTs and Western cohorts haven't reproduced this. Confounding by lifestyle and dietary pattern is plausible.
How it works
How to take it
What to track
Bottom line: Brewed tea is one of the safest dietary choices around. If you go to concentrated extracts, keep EGCG modest, take with food, and stop at any sign of liver trouble.
7 commercial forms
Compare the main delivery options and what they’re best suited for.
Green tea (brewed, sencha/dragonwell/gunpowder)
PreferredSteamed (Japanese) or pan-fired (Chinese) Camellia sinensis leaves. ~50–100 mg catechins per cup (~30 mg EGCG). The form with the strongest cardiovascular evidence and lowest hepatotoxicity risk.
Catechin absorption ~10–20% from brewed tea; well tolerated.
Matcha (powdered green tea)
ConcentratedStone-ground whole leaves of shade-grown green tea. Whisked into water, consuming the leaf solids. ~50–150 mg EGCG per ½ tsp serving — about 3–5× a brewed cup. Higher L-theanine and chlorophyll.
Higher catechin and caffeine per serving than brewed; mind total daily EGCG if you also use extracts.
Black tea (brewed)
Daily-drinkFully oxidized Camellia sinensis. Lower catechins (oxidized to theaflavins and thearubigins) but similar caffeine. Modest BP and lipid benefit in trials, slightly less than green tea.
Different polyphenols (theaflavins) with their own bioactivity; comparable safety to green tea.
Oolong tea (partially oxidized)
Middle groundPartially oxidized; flavor and chemistry intermediate between green and black. Some weight-loss and lipid trials use oolong with similar magnitude of effect.
Mix of catechins and theaflavins; well tolerated as brewed tea.
White tea
LightMinimally processed young leaves and buds. Lower caffeine, similar catechin profile to green tea. Less studied but presumed similar effects.
Same Camellia sinensis polyphenols at lower total dose per cup.
Green tea extract capsules (standardized to EGCG)
CautionConcentrated catechin extracts marketed for weight loss and antioxidant benefit. Real hepatotoxicity signal at ≥800 mg EGCG/day; USP and EFSA have issued warnings. If used, take with food and keep doses moderate.
Higher catechin absorption than brewed, but at the cost of acute liver injury risk.
Decaffeinated green tea
Caffeine-freeDecaffeinated by CO2 or water process; preserves most catechins. Good option for evening, pregnancy, or caffeine sensitivity. Cardiovascular benefit appears similar to caffeinated brewed tea.
Catechin content reduced ~10–20% by decaffeination; still meaningful.
Safety
Know the common side effects, key cautions, and who should avoid it.
Common side effects
Serious risks
Hepatotoxicity from concentrated green tea extracts — typically with EGCG ≥800 mg/day, often on an empty stomach. Presents as acute hepatitis (fatigue, nausea, dark urine, jaundice, elevated ALT/AST). USP and EFSA have issued warnings; the Minnesota Green Tea Trial established the clearest signal.
Reduced non-heme iron absorption — tannins bind dietary iron, lowering absorption by 20–80% when consumed with meals. Important for iron-deficient adults and people on plant-based diets.
Excessive caffeine — heavy tea consumption (6+ cups/day) plus other caffeine sources can drive total intake over 400 mg/day, causing anxiety, palpitations, or sleep disruption.
Who should avoid it
- People with liver disease, hepatitis, abnormal LFTs, or on hepatotoxic medications should avoid high-dose green tea extracts. Brewed tea is generally fine.
- Pregnant or breastfeeding women: keep total caffeine <200 mg/day (≈2 cups brewed green tea); avoid high-dose extracts.
- People with iron-deficiency anemia: take tea between meals rather than with iron-rich foods or iron supplements.
- People with anxiety disorders, panic attacks, or insomnia who are caffeine-sensitive — choose decaf or rooibos instead.
Pregnancy & breastfeeding
Brewed tea in moderation (≤2 cups green tea/day to keep total caffeine <200 mg/day) is generally considered safe in pregnancy. Avoid high-dose green tea extracts. Some sources flag a theoretical concern about folate metabolism interference at very high catechin intakes; this isn't an issue at typical brewed-tea amounts.
Bottom line: Brewed tea is one of the safest beverages. Concentrated extracts carry a real hepatotoxicity signal — keep EGCG well below 800 mg/day and stop at any liver symptoms.
Interactions
Green tea contains some vitamin K (~0.03 µg/mL brewed), and large daily volumes can reduce warfarin efficacy. Keep intake stable; check INR if changing your tea habit.
Tannins reduce non-heme iron absorption by 20–80%. Take iron supplements ≥1 hour before or 2 hours after tea, and don't drink tea with iron-rich meals if you're treating iron deficiency.
Additive cardiovascular stimulation from caffeine; heart rate, blood pressure, and anxiety can rise.
Concentrated green tea extracts add to overall hepatic stress; use brewed tea or skip the extract if you take any of these long-term.
EGCG can bind and inactivate the chemotherapy drug bortezomib in lab studies; avoid green tea (especially extracts) during bortezomib therapy.
Catechins have mild CYP3A4 inhibition in vitro; clinical magnitude is small for most patients but consider for narrow-therapeutic-window drugs.
Caffeine antagonizes sedative effects; don't drink caffeinated tea within 4–6 hours of bedtime if combining with sleep aids.
Food sources
| Food | Amount | %DV |
|---|---|---|
| Green tea, brewed | 1 cup (~30 mg EGCG, ~30 mg caffeine) | — |
| Matcha, prepared | 1/2 tsp (~70 mg EGCG, ~70 mg caffeine) | — |
| Black tea, brewed | 1 cup (~10 mg EGCG, ~50 mg caffeine) | — |
| Oolong tea, brewed | 1 cup (~30 mg EGCG, ~40 mg caffeine) | — |
| White tea, brewed | 1 cup (~20 mg EGCG, ~20 mg caffeine) | — |
| Decaffeinated green tea, brewed | 1 cup (~25 mg EGCG, <5 mg caffeine) | — |
| Bottled green tea (ready-to-drink) | 16 oz (~10–30 mg EGCG) | — |
Green tea, brewed
- Amount
- 1 cup (~30 mg EGCG, ~30 mg caffeine)
- %DV
- —
Matcha, prepared
- Amount
- 1/2 tsp (~70 mg EGCG, ~70 mg caffeine)
- %DV
- —
Black tea, brewed
- Amount
- 1 cup (~10 mg EGCG, ~50 mg caffeine)
- %DV
- —
Oolong tea, brewed
- Amount
- 1 cup (~30 mg EGCG, ~40 mg caffeine)
- %DV
- —
White tea, brewed
- Amount
- 1 cup (~20 mg EGCG, ~20 mg caffeine)
- %DV
- —
Decaffeinated green tea, brewed
- Amount
- 1 cup (~25 mg EGCG, <5 mg caffeine)
- %DV
- —
Bottled green tea (ready-to-drink)
- Amount
- 16 oz (~10–30 mg EGCG)
- %DV
- —
Choosing a product
What to look for on the label — and what to be skeptical of.
Look for…
Be skeptical of…
Frequently asked questions
Is drinking green tea as good as taking the extract?⌄
For most people, yes. Whole tea provides catechins, caffeine, and theanine at safer doses than concentrated extracts.
Why the liver warning on EGCG capsules?⌄
Concentrated high-dose extracts on an empty stomach have caused rare hepatotoxicity. Take with food and stay under ~800 mg EGCG/day.
References by claim
Cancer prevention
Filippini et al., 2020 — Cochrane Database of Systematic Reviews (2020) link
Blood pressure
Hartley et al., 2013 — Cochrane Database of Systematic Reviews (2013) link
Safety
US Pharmacopeia — Green Tea Catechin Safety — Oketch-Rabah et al., 2020 (USP review) (2020) link
Modest weight loss (green tea catechins + caffeine)
Memorial Sloan Kettering — About Herbs: Green Tea — MSKCC Integrative Medicine (2024) link
Track Camellia sinensis with Pilora
Set up dose reminders, check interactions, and join the community in the Pilora iPhone app.
Coming to App StoreDisclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you’re pregnant, breastfeeding, on medications, or managing a chronic condition.