Green tea: small measured effects and two drug clashes

Across 36 randomized trials in adults, green tea lowered systolic and diastolic blood pressure by about 1.1 mmHg each (systolic 95% CI -1.98 to -0.18). Those trials mixed the drink with supplements and disagreed a lot with each other. An older meta-analysis of 20 trials with 1536 people found systolic pressure 1.94 mmHg lower and LDL cholesterol 7.3 mg/dL (0.19 mmol/l) lower. Weight moved only a little. In a meta-analysis of trials in adults, whose abstract does not give the number of trials, green tea supplements trimmed 1.6 lb (0.74 kg) and about 0.39 in (1 cm) of waist. The EU refused a fat burning claim for a guarana and green tea extract, and a claim that green tea catechins cut carbohydrate absorption by 25 percent. A cup of hot brewed green tea (240 g) carries about 29 mg caffeine and 2.4 calories in US survey data, a single figure that shifts with the leaf and the brewing time.

The numbers, per 3.5 oz (100 g)

As people eat it, per 3.5 oz (100 g)

How much is actually in it

• A cup of hot brewed green tea has about 29 mg of caffeine in USDA survey data, so 200 mg a day equals roughly 7 cups. — USDA FNDDS 2021-2023, food code 92303010, Tea, hot, leaf, green Evidence C source
  Caffeine 12 mg/100 g; 1 cup (240 g) 28.8 mg; decaffeinated 0 mg
• UK composition tables list a green tea infusion with only trace energy and carbohydrate and zero fat. — CoFID 2021, Tea, green, infusion (17-171) (n = 1 food) Evidence E source
  Energy Tr, carbohydrate Tr, fat 0.0 g, fiber 0.0 g per 3.5 oz (100 g)

What a real portion looks like

• A cup of hot brewed green tea (240 g) carries about 29 mg caffeine and 2.4 calories in US survey data. — USDA FNDDS, Tea, hot, leaf, green (n = 1 food code) Evidence E source
  Per 100 g: caffeine 12 mg, energy 1 calories; 1 cup 240 g: caffeine 28.8 mg, energy 2.4 calories

What your body absorbs

• In 30 women with low iron stores, 300 mg EGCG a day cut nonheme iron absorption by 27% and 150 mg by 14% versus placebo. — 30 healthy women with low iron stores, 8 days per treatment, crossover (n = 30) Evidence B source
  Relative nonheme iron absorption -14% with 150 mg EGCG and -27% with 300 mg EGCG versus placebo
• A systematic safety review of 159 human intervention studies found liver harm only with concentrated catechin boluses, not brewed tea, and derived a safe intake of 338 mg EGCG a day as a solid dose. — 159 human intervention studies plus toxicology studies of green tea preparations in adults (n = 159 studies) Evidence C source
  Safe intake 338 mg EGCG/day for solid bolus; observed safe level 704 mg EGCG/day in beverage form
• A case report describes severe iron deficiency anemia in a woman after three months of moderate green tea drinking, which did not return once her tea habit changed. — 1 woman, case report (n = 1) Evidence D source
  Hemoglobin fell by 6.9 g/dl over three months; no recurrence after changing tea intake

What cooking and storage change

• A review of 88 studies found fluoride release from tea rises with brewing time, and green tea infusions average 1.37 mg/L, below black and brick tea. — 88 global studies of fluoride in tea leaves and infusions (n = 88 studies) Evidence C source
  Brewing time vs fluoride release r = 0.82; green tea 1.37 mg/L vs black 2.73 and brick 4.78 mg/L

What it does to your health

• A Cochrane review found one usable trial: cutting caffeine by about 182 mg a day in heavy coffee drinkers in later pregnancy did not change birthweight or preterm birth in 1,197 women. — regular coffee drinkers (3+ cups/day) in the second and third trimester, caffeinated vs decaffeinated instant coffee (n = 1,197) Evidence A source
  Birthweight MD 20.00 g (95% CI -48.68 to 88.68); preterm birth RR 0.81 (0.48 to 1.37); small-for-gestational age RR 0.97 (0.57 to 1.64); low quality evidence
• An umbrella review of meta-analyses of observational studies found caffeine or coffee in pregnancy linked to 34% higher odds of low birth weight. — pregnant women in meta-analyses of cohort, case-control and cross-sectional studies (n = 13 systematic reviews, 15 meta-analyses) Evidence C source
  Caffeine/coffee and low birth weight: OR 1.34 (95% CI 1.14 to 1.57)
• The Cochrane authors concluded that green tea preparations give a small, statistically non-significant weight loss and do not help keep lost weight off. — overweight or obese adults in RCTs of green tea preparations Evidence A source
  Small non-significant weight loss; no significant effect on weight maintenance
• A 2025 meta-analysis of randomized trials in adults found green tea supplements lowered body weight by 1.6 lb (0.74 kg) and waist by about 0.39 in (1 cm) on average. — adults in randomized controlled trials of green tea supplementation Evidence A source
  Body weight WMD -1.6 lb (95% CI -2.1 to -1.1; metric: -0.74 kg, -0.97 to -0.51); BMI -0.29 kg/m2; waist -0.41 in (-1.04 cm); body fat -0.65%
• A 2021 umbrella review pooling 13 meta-analyses put the effect of green tea on weight at a weighted mean difference of -0.89. — 13 meta-analyses of green tea intake and cardiometabolic risk factors (n = 13 meta-analyses) Evidence A source
  Weight WMD -0.89 (95% CI -1.43 to -0.34); waist WMD -1.01 (95% CI -1.63 to -0.39)
• A meta-analysis of 8 RCTs found EGCG raised energy expenditure by about 158 kJ (38 calories) a day, while fat burning did not change significantly. — randomized controlled trials of EGCG in humans (n = 8 trials) Evidence A source
  Energy expenditure MD 158.05 kJ/day (95% CI 4.72 to 311.38); respiratory quotient MD -0.02; fat oxidation not significant
• Across 36 RCTs in adults, green tea supplementation lowered systolic blood pressure by about 1.1 mmHg and diastolic by about 1.1 mmHg. — adults 18 years and older in 36 RCTs of green tea supplementation versus control or placebo (n = 36 RCTs) Evidence A source
  SBP WMD -1.08 mmHg (95% CI -1.98 to -0.18), DBP WMD -1.09 mmHg (95% CI -1.67 to -0.50), I2 74-85%
• A meta-analysis of 20 RCTs with 1536 people found green tea lowered LDL cholesterol by 7.3 mg/dL (0.19 mmol/l) and systolic pressure by 1.94 mmHg. — participants of 20 randomized clinical trials of green tea (n = 1536) Evidence A source
  SBP MD -1.94 mmHg (95% CI -2.95 to -0.93); total cholesterol MD -5 mg/dL (-7.7 to -2.7; metric: -0.13 mmol/l, -0.2 to -0.07); LDL MD -7.3 mg/dL (-12 to -3.5; metric: -0.19 mmol/l, -0.3 to -0.09)
• In 38 RCTs, green tea improved oxidative stress markers but did not change CRP, IL-6 or TNF-alpha. — adults in 38 RCTs lasting more than 2 weeks (n = 38 RCTs) Evidence A source
  MDA WMD -0.40 umol/L (95% CI -0.63 to -0.18); TAC +0.09 mmol/L; CRP WMD 0.01 mg/L (-0.14 to 0.15), no change

Safety, limits and interactions

• In a meta-analysis of 34 randomized trials, polyphenol supplements such as tea catechins lowered serum iron by about 14 ug/dL and transferrin saturation by about 3 points without changing ferritin. — participants in randomized controlled trials of dietary polyphenol supplementation (n = 34 RCTs) Evidence A source
  Serum iron -13.72 ug/dL (95% CI -20.74 to -6.71); transferrin saturation -3.10% (-4.93 to -1.27); ferritin -9.34 ng/mL (-28.55 to 9.87, not significant)
• In 254 pregnant women in Tokyo, drinking more green or oolong tea was linked to lower serum folate after adjusting for folate intake and supplements. — healthy women with a singleton pregnancy at a prenatal clinic in metropolitan Tokyo (n = 254) Evidence C source
  High green or oolong tea (>57.3 mL per 1,000 calories): beta -0.131, p = 0.016 for serum folate
• In a 12-month trial of 1,021 women, high-dose green tea extract raised liver enzymes, and 5.1% developed liver test abnormalities, about 7 times the odds on placebo. — women with normal baseline liver enzymes in a randomized placebo-controlled trial of green tea extract for 12 months (n = 1,021) Evidence B source
  ALT +5.4 U/L (95% CI 3.6 to 7.1) vs placebo; 26 of 513 (5.1%) with moderate or worse abnormalities; OR 7.0 (95% CI 2.4 to 20.3)
• In a trial of 10 healthy volunteers, drinking 24 fl oz (700 mL) of green tea a day for 14 days cut blood levels of the beta-blocker nadolol by 85% and blunted its effect on blood pressure. — healthy volunteers given a single 30 mg dose of nadolol after 14 days of green tea or water (n = 10) Evidence B source
  Nadolol Cmax -85.3% and AUC -85.0% (P < 0.01); smaller drop in systolic blood pressure
• A green tea extract drink with about 300 mg EGCG cut blood levels of the blood pressure drug lisinopril by about two thirds in 10 healthy volunteers. — 10 healthy volunteers, single 10 mg lisinopril dose with 6.8 fl oz (200 mL) green tea extract or water, crossover (n = 10) Evidence B source
  Cmax ratio 0.289 (90% CI 0.226-0.352); AUC ratio 0.337 (90% CI 0.269-0.405)
• One cup of brewed green tea taken with the beta blocker nadolol cut its blood exposure by about 63% in 11 healthy volunteers, and by 46% when drunk an hour before. — 11 healthy volunteers, nadolol with 5.1 fl oz (150 mL) brewed green tea, 1 hour after it, or with water, crossover (n = 11) Evidence B source
  Nadolol AUC ratio 0.371 (90% CI 0.303-0.439) concomitant; 0.536 (0.406-0.665) with tea 1 hour before
• Across 34 RCTs of green tea extracts, liver-related adverse events were rare, with an odds ratio of 2.1 versus placebo that was not significant. — participants of 34 randomized trials of green tea extracts (n = 34 RCTs) Evidence A source
  Summary OR 2.1 (95% CI 0.5 to 9.8); 8 events in 7 subjects on green tea vs 1 on control, mostly mild enzyme rises

What people believe that the data does not support

• The Nordic Nutrition Recommendations 2023 review advises pregnant women not to exceed 200 mg of caffeine a day, the level EFSA set as safe for the fetus. — pregnant women, Nordic and Baltic dietary guidelines Evidence C source
  Caffeine ceiling 200 mg/day in pregnancy (EFSA)
• According to ACOG, caffeine below 200 mg a day does not appear to be a major factor in miscarriage or preterm birth. — pregnant women, ACOG Committee Opinion No. 462 Evidence E source
  <200 mg/day caffeine: not a major contributing factor in miscarriage or preterm birth; growth restriction undetermined
• EFSA found that green tea catechin supplements at 800 mg EGCG a day or more raised liver enzymes in clinical trials. — adults in the EU consuming green tea infusions or green tea catechin food supplements Evidence E source
  800 mg EGCG/day or more as a supplement: statistically significant increase in serum transaminases
• In a 2023 network meta-analysis of 111 RCTs on 18 supplements, green tea gave a small 2.8 lb (1.25 kg) weight loss, with certainty of evidence rated low. — adults with overweight or obesity in randomized trials of nutraceuticals (n = 6171) Evidence A source
  Green tea vs placebo MD -2.8 lb (95% CI -3.7 to -1.8; metric: -1.25 kg, -1.68 to -0.82), low certainty
• EFSA found traditional green tea safe at usual intakes, but supplements giving 800 mg EGCG a day or more raised liver enzymes in clinical trials. — adults in the EU consuming green tea infusions or green tea catechin food supplements Evidence E source
  Usual intake from tea 90 to 300 mg EGCG/day; supplements 5 to 1,000 mg/day; 800 mg EGCG/day or more raised serum transaminases
• NCCIH says the catechins and caffeine in green tea and its extracts may have a modest effect on body weight. — general public Evidence E source
  Modest effect on body weight
• The EU did not authorize a label claim that a green tea and guarana extract helps to burn fat. — foods sold in the EU Evidence E source
  Claim status: non-authorized
• Green tea supplementation trimmed body weight by 1.6 lb (0.74 kg) and waist by about 0.39 in (1 cm) on average in a meta-analysis of RCTs in adults. — adults in RCTs of green tea supplementation, searched to February 2024 Evidence A source
  Body weight WMD -1.6 lb (95% CI -2.1 to -1.1; metric: -0.74 kg, -0.97 to -0.51); BMI -0.29 kg/m2; waist -0.41 in (-0.61 to -0.21; metric: -1.04 cm, -1.55 to -0.53); body fat -0.65%
• The EU did not authorize a claim that a guarana and green tea extract combination helps to burn fat. — EU Register on nutrition and health claims Evidence E source
  Claim status non-authorized
• The EU did not authorize a claim that green tea catechins cut carbohydrate absorption by 25% and reduce visceral fat. — EU Register on nutrition and health claims Evidence E source
  Claim status non-authorized

Who this works differently for

• A 2025 systematic review of 14 trials found that adding the green tea catechin EGCG to nifedipine in preeclampsia shortened the time to blood pressure control by about 14 minutes, on low-certainty evidence from one trial of 349 women. — women with preeclampsia in randomized controlled trials of polyphenol-containing products (n = 14 trials; EGCG outcome 1 trial, 349 women) Evidence A source
  Time to BP control MD -14.10 min (95% CI -18.46 to -9.74); time to next hypertensive crisis MD +3.10 h (2.35 to 3.85); low certainty
• In a double-blind trial in 404 women with gestational diabetes in the third trimester, 500 mg EGCG a day until term was reported to improve maternal glucose measures and reduce newborn complications versus placebo. — pregnant women during their third trimester diagnosed with GDM (n = 404 randomized (326 completed)) Evidence B source
  500 mg EGCG daily vs placebo: improved maternal diabetic parameters and fewer neonatal complications (no effect sizes in abstract)
• In a Chinese case-control study, women who drank tea daily around conception had about 3 times the odds of a neural tube defect pregnancy, even after adjusting for folic acid use. — NTD cases and term controls in 4 rural counties of Shanxi Province, northern China, 2002-2007 (n = 631 cases, 857 controls) Evidence C source
  Daily tea vs none: OR 3.1 (95% CI 1.4 to 7.0); adjusted OR 3.4 (1.4 to 8.3)
• In 39 women of reproductive age given 720 mg of green tea extract EGCG a day for 30 days, folate stayed in the normal range, including in carriers of MTHFR or DHFR variants. — women aged 18 to 40 years, with or without uterine fibroids, not pregnant (n = 39) Evidence C source
  Folate within normal range in all subjects during 30 days of EGCG 720 mg/day
• A 2024 meta-analysis of 16 trial arms in women with overweight or obesity found green tea lowered weight by 2.7 lb (1.23 kg). — overweight and obese women in randomized controlled trials (n = 16 RCT arms) Evidence A source
  Body weight WMD -2.7 lb (95% CI -4.7 to -0.73; metric: -1.23 kg, -2.13 to -0.33); BMI -0.47 kg/m2; waist -1.4 in (-3.46 cm); doses of 1000 mg/day or more WMD -3 lb (-1.38 kg)
• In a 12-month double-blind trial, decaffeinated green tea extract with 843 mg EGCG a day did not change BMI or fat mass in 121 overweight or obese postmenopausal women. — overweight or obese postmenopausal women aged 50 to 70 in the Minnesota Green Tea Trial (n = 121) Evidence B source
  BMI change -0.13 vs -0.05 (P = 0.61); total fat mass -0.66 vs -0.26 lb (-0.30 vs -0.12 kg) (P = 0.40); body fat -0.15% vs -0.15% over 12 months
• In women with polycystic ovary syndrome, a meta-analysis of 6 RCTs with 235 women found tea supplements lowered body weight by 6 lb (2.7 kg). — women with polycystic ovary syndrome in randomized controlled trials of tea versus placebo (n = 235) Evidence A source
  Body weight WMD -6 lb (95% CI -11 to -1; metric: -2.71 kg, -4.95 to -0.46), I2 0%; no difference in BMI or waist; adverse reactions RR 1.45 (95% CI 0.30 to 6.90)
• In postmenopausal women taking 843 mg EGCG a day for a year, ALT rose by about 80% in carriers of the UGT1A4 A/C genotype against about 30% in C/C carriers. — 400 postmenopausal women on high-dose green tea extract in the Minnesota Green Tea Trial (N = 1,075), 12 months (n = 400) Evidence C source
  ALT change at months 6 and 9: +78.1% and +82.1% (A/C) vs +28.0% and +30.1% (C/C)
• In two Shanghai cohorts of over 127,000 middle-aged adults, green tea drinkers had a 16 to 22% lower risk of new kidney stones than non-drinkers. — Shanghai Men's Health Study (n = 58 054) and Shanghai Women's Health Study (n = 69 166), aged 40-74 (n = 127220) Evidence C source
  Green tea drinkers HR 0.78 (95% CI 0.69-0.88) in men, 0.84 (0.74-0.95) in women
• In 62 girls aged 6 to 10 with obesity, 400 mg a day of decaffeinated green tea polyphenols for 12 weeks caused no adverse effects on liver, kidney or blood markers. — 62 girls with obesity aged 6 to 10 years, 12 weeks (n = 62) Evidence B source
  No significant differences in hepatic, renal or blood indicators; uric acid fell -48.0 vs -0.01 umol/L; no adverse effects reported

What is still unknown

• In 1,724 Chinese pregnant women, mostly green tea drinkers among those who drank tea, plasma folate did not differ between tea drinkers and non-drinkers. — pregnant women during early second trimester in three cities/counties in China, 2011-2012 (n = 1,724) Evidence C source
  Median plasma folate 48.7 nmol/L (tea) vs 45.2 nmol/L (no tea), no statistical difference
• A Cochrane review pooled 6 trials of green tea run outside Japan, with 532 participants, and found a weight difference of -0.09 lb (95% CI -1.1 to 0.88; metric: -0.04 kg, -0.5 to 0.4). — overweight or obese adults in RCTs of green tea preparations lasting at least 12 weeks (n = 532) Evidence A source
  Weight MD -0.09 lb (95% CI -1.1 to 0.88; metric: -0.04 kg, -0.5 to 0.4), I2 18%, 6 trials outside Japan, 532 participants; Japanese trials not pooled

The bottom line

In 38 trials, green tea lowered the oxidation marker MDA by 0.40 umol/L and left CRP, IL-6 and TNF-alpha unchanged. These are blood markers, and none of the trials above counted heart attacks or strokes. The cautions are medicines, the liver and iron. One 5.1 fl oz (150 mL) cup of brewed green tea taken with the beta blocker nadolol cut its blood exposure by about 63 percent in 11 healthy volunteers after a single dose, and by 46 percent when the tea came an hour earlier. A green tea extract drink with about 300 mg EGCG cut blood levels of the blood pressure drug lisinopril by about two thirds in 10 healthy volunteers, and nobody measured what that did to blood pressure. If you take either drug, how you time your tea is a question for your prescriber. Liver problems track concentrated extracts. Across 34 randomized trials of extracts, liver events were rare, 8 events in 7 people on green tea against 1 on control, mostly mild enzyme rises, and the odds ratio of 2.1 (95% CI 0.5 to 9.8) did not reach significance. A safety review of 159 human studies found liver harm only with concentrated catechin doses taken in one go, and none with brewed tea. It derived a safe intake of 338 mg EGCG a day as a solid dose, a figure the authors calculated and not a limit set by any agency. In a year-long trial of 843 mg EGCG a day in postmenopausal women, 98 percent of them white, ALT rose about 80 percent in carriers of the UGT1A4 A/C genotype against about 30 percent in C/C carriers. In 30 women with low iron stores, pure EGCG cut nonheme iron absorption by 27 percent at 300 mg a day and 14 percent at 150 mg against placebo, and the authors say the effect is smaller than for black tea. One case report describes severe iron deficiency anemia in a woman after three months of moderate green tea drinking, with hemoglobin down 6.9 g/dl, that did not return once she changed her tea habit. It is one case. In 62 girls aged 6 to 10 with obesity, 400 mg a day of a decaffeinated green tea polyphenol extract for 12 weeks caused no adverse effects on liver, kidney or blood markers. That was an extract, given to girls only. Two Shanghai cohorts of 127,220 adults aged 40 to 74 link drinking green tea with fewer new kidney stones (men HR 0.78, 95% CI 0.69 to 0.88, women HR 0.84, 95% CI 0.74 to 0.95). The stones were self-reported, and this is an association and not a tested effect. Fluoride release from tea rises with brewing time (r = 0.82) across 88 measurement studies, and green tea infusions averaged 1.37 mg/L against 2.73 for black and 4.78 for brick tea. We found no data on green tea in pregnancy.

Compared with other foods

Sources

1. ev-gtpg-08 · dataset
   Tea, hot, leaf, green, FNDDS code 92303010, fdc_id 2710490: Caffeine 12 MG per 100 g; 1 cup 240 g, 28.8 MG
   USDA FNDDS 2021-2023, food code 92303010, Tea, hot, leaf, green (fdc_id 2710490) · checked 2026-10-07
2. grtea-r7-02 · composition dataset
   Tea, green, infusion (17-171): Energy Tr kcal | Carbohydrate Tr g | Fat 0.0 g | AOAC fibre 0.0 g | Cholesterol 0.0 mg
   CoFID 2021 (Public Health England, OGL v3.0), code 17-171 Tea, green, infusion · checked 2026-09-29
3. grtea-r7-01 · composition dataset
   Tea, hot, leaf, green, fdc_id 2710490, per 100 g: Caffeine 12 mg; Energy 1 kcal; 1 cup 240 g: Caffeine 28.8 mg; Energy 2.4 kcal; 1 fl oz 30 g: Caffeine 3.6 mg
   USDA FNDDS, Tea, hot, leaf, green, FDC 2710490 · checked 2026-09-29
4. grtea-r7-07 · RCT
   The study was designed to show the maximum inhibitory action of EGCG by selecting 30 healthy women with low iron stores. Treatments were 150 mg, 300 mg EGCG and placebo each for 8 consecutive study days with a wash-out period of 14 days between treatments. ... Results showed a relative nonhaem iron absorption reduction of 14% with 150mg EGCG and 27% for 300mg EGCG treatment compared to placebo.
   Phytomedicine, 2005 · checked 2026-09-29
5. grtea-r7-11 · systematic review
   A review of adverse event (AE) data from 159 human intervention studies yielded findings consistent with toxicological evidence in that a limited range of concentrated, catechin-rich green tea preparations resulted in hepatic AEs in a dose-dependent manner when ingested in large bolus doses, but not when consumed as brewed tea or extracts in beverages or as part of food. ... A safe intake level of 338 mg EGCG/day for adults was derived from toxicological and human safety data for tea preparations ingested as a solid bolus dose. An Observed Safe Level (OSL) of 704 mg EGCG/day might be considered for tea preparations in beverage form based on human AE data.
   Regul Toxicol Pharmacol, 2018 · checked 2026-09-29
6. grtea-r7-16 · case report
   Consequently, it is uncommon for hemoglobin levels to plummet by 6.9 g/dl solely due to moderate tea consumption over a span of three months. We present a case of severe iron-deficiency anemia in a woman following short-term, moderate green tea consumption. After modifying her tea intake regimen, there was no recurrence of anemia.
   Heliyon, 2024 · checked 2026-09-29
7. grtea-r7-13 · scoping review
   Brewing time strongly correlates with F- release (r = 0.82, p < 0.001), with black tea bags reaching 6.01 mg/L after 30 min. ... F- concentrations vary significantly by tea type: brick tea (4.78 mg/L) > black tea (2.73 mg/L) > green tea (1.37 mg/L) > white tea (0.49 mg/L) > herbal tea (0.17 mg/L).
   Crit Rev Food Sci Nutr, 2025 · checked 2026-09-29
8. ev-gtpg-01 · Cochrane review of RCTs
   Caffeinated instant coffee (568 women) was compared with decaffeinated instant coffee (629 women) and it was found that reducing the caffeine intake of regular coffee drinkers (3+ cups/day) during the second and third trimester by an average of 182 mg/day did not affect birthweight (g) (mean difference (MD) 20.00, 95% confidence interval (CI) -48.68 to 88.68; one study, 1197 participants; low quality evidence), preterm birth (risk ratio (RR) 0.81, 95% CI 0.48 to 1.37; one study, 1153 participants; low quality evidence) or small-for-gestational age (RR 0.97, 95% 0.57 to 1.64; one study, 1150 participants).
   Cochrane Database of Systematic Reviews, 2015, CD006965 (Jahanfar and Jaafar), Effects of restricted caffeine intake by mother on fetal, neonatal and pregnancy outcomes · checked 2026-10-07
9. ev-gtpg-05 · umbrella review
   The following 13 maternal factors were identified as risk factors for low birth weight: crack/cocaine (odds ratio [OR] 2.82, 95% confidence interval [CI] 2.26-3.52), infertility (OR 1.34, 95% CI 1.2-1.48), smoking (OR 2.00, 95% CI 1.76-2.28), periodontal disease (OR 2.41, 95% CI 1.67-3.47), depression (OR 1.84, 95% CI 1.34-2.53), anemia (OR 1.32, 95% CI 1.13-1.55), caffeine/coffee (OR 1.34, 95% CI 1.14-1.57), heavy physical workload (OR 1.87, 95% CI 1.00-3.47), lifting ≥ 11 kg (OR 1.59, 95% CI 1.02-2.48), underweight (OR 1.79, 95% CI 1.20-2.67), alcohol (OR 1.23, 95% CI 1.04-1.46), hypertension (OR 3.90, 95% CI 2.73-5.58), and hypothyroidism (OR 1.40, 95% CI 1.01-1.94).
   BMC Pregnancy Childbirth, 2024 · checked 2026-10-07
10. ev-gtwl-02 · Cochrane review of RCTs
    Green tea preparations appear to induce a small, statistically non-significant weight loss in overweight or obese adults. Because the amount of weight loss is small, it is not likely to be clinically important. Green tea had no significant effect on the maintenance of weight loss.
    Cochrane Database of Systematic Reviews, 2012, CD008650, Green tea for weight loss and weight maintenance in overweight or obese adults · checked 2026-10-06
11. ev-gtwl-03 · meta-analysis of RCTs
    Green tea supplementation reduced BW (WMD: -0.74 kg; 95% CI: -0.97, -0.51), BMI (WMD: -0.29 kg/m2; 95% CI: -0.38, -0.19), WC (WMD: -1.04 cm; 95% CI: -1.55, -0.53), BFP (WMD: -0.65%; 95% CI: -1.03, -0.27), and leptin (WMD: -0.92 ng/ml; 95% CI: -1.71, -0.14), but did not change adiponectin levels (WMD: 0.20 µg/ml; 95% CI: -0.17, 0.57).
    Int J Food Sci Nutr, 2025 · checked 2026-10-06
12. ev-gtwl-06 · umbrella review
    Meta-meta-analysis revealed significant effects of GT on weight and waist circumference with weighted mean difference (WMD) of -0.89 (95% CI -1.43 to -0.34, p < 0.001) and -1.01 (95% CI -1.63 to -0.39, p < 0.001)
    Nutr Metab Cardiovasc Dis, 2022 · checked 2026-10-06
13. ev-gtwl-07 · meta-analysis of RCTs
    The meta-analysis results of verities of studies in terms of dose and length of duration revealed that EGCG supplementation provided significant mean difference (MD) when compared with placebo for RQ [MD: -0.02; 95% confidence intervals (95% CI), -0.04 to 0.00; I2=67%; P=.01] and EE [MD: 158.05 kJ/day; 95% CI, 4.72 to 311.38; I2=0%; P=.04] in fixed-effect approach. Changes in FOX did not reach the level of statistical significance.
    J Nutr Biochem, 2017 · checked 2026-10-06
14. grtea-r7-03 · meta-analysis of RCTs
    A total of 36 RCTs were included. Green tea reduced SBP (WMD: -1.08 mmHg; 95% CI: -1.98, -0.18; I2 = 85.0%) and DBP (WMD: -1.09 mmHg; 95% CI: -1.67, -0.50; I2 = 74.0%).
    Blood Press, 2025 · checked 2026-09-29
15. grtea-r7-04 · meta-analysis of RCTs
    As many as 474 citations were identified and 20 RCTs comprising 1536 participants were included. There were variations in the designs of the RCTs. A meta-analysis revealed a significant reduction in systolic blood pressure favouring green tea (MD: -1.94 mmHg; 95% CI: -2.95 to -0.93; I(2) = 8%; p = 0.0002). Similar results were also observed for total cholesterol (MD: -0.13 mmol/l; 95% CI: -0.2 to -0.07; I(2) = 8%; p < 0.0001) and LDL cholesterol (MD: -0.19 mmol/l; 95% CI: -0.3 to -0.09; I(2) = 70%; p = 0.0004).
    Nutr Metab Cardiovasc Dis, 2014 · checked 2026-09-29
16. grtea-r7-06 · meta-analysis of RCTs
    Out of 1264 records initially retrieved, 38 RCTs were included. Supplementation with green tea improved the following indicators: IL-1β (weighted mean difference (WMD): -0.10 pg/mL; 95% CI: -0.15, -0.06), MDA (WMD: -0.40 mcmol/L; 95 % CI: -0.63, -0.18), TAC (WMD: 0.09 mmol/L; 95% CI: 0.05, 0.13), SOD (WMD: 17.21 u/L; 95% CI: 3.24, 31.19), and GPX (WMD: 3.90 u/L; 95% CI: 1.85, 5.95); but failed to improve others, including CRP (WMD: 0.01 mg/L; 95% CI: -0.14, 0.15), IL-6 (WMD: -0.34 pg/mL; 95% CI:-0.94, 0.26), and TNF-α (WMD: -0.07 pg/mL; 95% CI: -0.42, 0.28).
    J Nutr Sci, 2025 · checked 2026-09-29
17. ev-gtpg-03 · meta-analysis of randomized controlled trials
    Polyphenol supplementation had an inhibitory effect on the SI concentration (-13.72 μg/dL; 95% CI: -20.74, -6.71) and TS (-3.10%; 95% CI: -4.93, -1.27), with no effect on ferritin (-9.34 ng/mL; 95% CI: -28.55, 9.87).
    Am J Clin Nutr, 2021 · checked 2026-10-07
18. ev-gtpg-10 · cross-sectional study
    A multiple regression analysis revealed the high consumption of green tea or oolong tea to be associated with a low serum folate level during pregnancy, after adjusting for confounding variables including dietary folate intake and use of folic acid supplements or multivitamins (β = -0.131, p = 0.016).
    Biosci Trends, 2010 · checked 2026-10-07
19. ev-gtwl-09 · RCT
    Overall, 26 (5.1%) women in GTE developed moderate or more severe abnormalities in any liver function measure during the intervention period, yielding an OR of 7.0 (95% CI, 2.4-20.3) for developing liver function abnormalities as compared with those in the placebo arm.
    Cancer Prev Res (Phila), 2017 · checked 2026-10-06
20. ev-gtwl-11 · RCT
    Green tea markedly decreased the maximum plasma concentration (C(max)) and area under the plasma concentration-time curve (AUC(0-48)) of nadolol by 85.3% and 85.0%, respectively (P < 0.01), without altering renal clearance of nadolol.
    Clin Pharmacol Ther, 2014 · checked 2026-10-06
21. grtea-r7-08 · RCT
    In an open-label, randomized, single-center, 2-phase crossover study, 10 healthy subjects ingested 200 mL of an aqueous solution of GTE containing ~ 300 mg of (-)-epigallocatechin gallate, a major catechin component in green tea, or water (control) when receiving 10 mg of lisinopril after overnight fasting. The geometric mean ratio (GTE/control) for maximum plasma concentration and the area under the plasma concentration-time curve of lisinopril were 0.289 (90% confidence interval (CI) 0.226-0.352) and 0.337 (90% CI 0.269-0.405), respectively.
    Clin Transl Sci, 2021 · checked 2026-09-29
22. grtea-r7-09 · RCT
    In a randomized 3-phase crossover study, 11 healthy volunteers received an oral administration of nadolol with, or 1 hour after preingestion of brewed GT, or with water in a volume of 150 mL. RESULTS: Geometric mean ratio with 90% confidence interval for nadolol AUC0-48 was 0.371 (0.303-0.439) with concomitant GT. In addition, ingestion of GT 1 hour before nadolol administration resulted in a significant reduction of nadolol AUC0-48 with geometric mean ratio of 0.536 (0.406-0.665).
    Br J Clin Pharmacol, 2020 · checked 2026-09-29
23. grtea-r7-10 · meta-analysis of RCTs
    Of these, liver-related adverse events were reported in four trials; these adverse events involved seven subjects (eight events) in the green tea intervention group and one subject (one event) in the control group. The summary odds ratio, estimated using a meta-analysis method for sparse event data, for intervention compared with placebo was 2.1 (95% confidence interval: 0.5-9.8). The few events reported in both groups were elevations of liver enzymes.
    Eur J Clin Nutr, 2016 · checked 2026-09-29
24. ev-gtpg-06 · scoping review
    Pregnant women should not exceed the recommended daily dose of caffeine intake of 200 mg set by the European Food Safety Authority as a safe level for the fetus.
    Food Nutr Res, 2024 · checked 2026-10-07
25. ev-gtpg-07 · professional society committee opinion
    Moderate caffeine consumption (less than 200 mg per day) does not appear to be a major contributing factor in miscarriage or preterm birth.
    Obstetrics and Gynecology, 2010, 116(2 Pt 1):467-468, ACOG Committee Opinion No. 462: Moderate caffeine consumption during pregnancy · checked 2026-10-07
26. ev-gtpg-13 · agency position
    Based on the available data on the potential adverse effects of green tea catechins on the liver, the Panel concluded that there is evidence from interventional clinical trials that intake of doses equal or above 800 mg EGCG/day taken as a food supplement has been shown to induce a statistically significant increase of serum transaminases in treated subjects compared to control.
    EFSA Journal, 2018, 16(4):5239, Scientific opinion on the safety of green tea catechins (EFSA ANS Panel) · checked 2026-10-06
27. ev-gtwl-04 · network meta-analysis of RCTs
    Supplementations with green tea (MD: -1.25 kg, 95%CI: -1.68, -0.82) and glucomannan (MD: -1.36 kg, 95%CI: -2.17, -0.54) demonstrated small weight loss, also the certainty of evidence was rated low.
    Pharmacol Res, 2023 · checked 2026-10-06
28. ev-gtwl-10 · agency position
    Based on the available data on the potential adverse effects of green tea catechins on the liver, the Panel concluded that there is evidence from interventional clinical trials that intake of doses equal or above 800 mg EGCG/day taken as a food supplement has been shown to induce a statistically significant increase of serum transaminases in treated subjects compared to control.
    EFSA Journal, 2018, 16(4):5239, Scientific opinion on the safety of green tea catechins (EFSA ANS Panel) · checked 2026-10-06
29. ev-gtwl-12 · agency position
    The catechins and caffeine in green tea and its extracts may have a modest effect on body weight.
    NCCIH (NIH), Green Tea, last updated February 2025 · checked 2026-10-06
30. ev-gtwl-13 · regulatory register entry
    POL-HC-8415 A combination of Paullinia cupana Kunth (guarana) and Camellia sinensis (L.) Kuntze (green tea) extracts Helps to burn fat -/- Non-authorised
    EU Register on nutrition and health claims, claim POL-HC-8415, snapshot 2026-09-21 · checked 2026-10-06
31. grtea-r7-05 · meta-analysis of RCTs
    Green tea supplementation reduced BW (WMD: -0.74 kg; 95% CI: -0.97, -0.51), BMI (WMD: -0.29 kg/m2; 95% CI: -0.38, -0.19), WC (WMD: -1.04 cm; 95% CI: -1.55, -0.53), BFP (WMD: -0.65%; 95% CI: -1.03, -0.27), and leptin (WMD: -0.92 ng/ml; 95% CI: -1.71, -0.14), but did not change adiponectin levels (WMD: 0.20 µg/ml; 95% CI: -0.17, 0.57).
    Int J Food Sci Nutr, 2025 · checked 2026-09-29
32. grtea-r7-17 · agency decision
    POL-HC-8415 A combination of Paullinia cupana Kunth (guarana) and Camellia sinensis (L.) Kuntze (green tea) extracts Helps to burn fat -/- Non-authorised
    EU Register on nutrition and health claims, claim POL-HC-8415, snapshot 2026-09-21 · checked 2026-09-29
33. grtea-r7-18 · agency decision
    POL-HC-7101 Flavonoids from green tea, apple and onion Flavonoids, especially catechins from green tea, reduce the absorption of carbohydrates by 25%. Carbohydrates account for 49% of total energy. Thus the weight slimming effect is a total of 12%. Reduces visceral fat Non-authorised
    EU Register on nutrition and health claims, claim POL-HC-7101, snapshot 2026-09-21 · checked 2026-09-29
34. ev-gtpg-02 · meta-analysis of randomized controlled trials
    In women with preeclampsia, the addition of epigallocatechin gallate (EGCG) to nifedipine may reduce the time needed to achieve blood pressure control (mean difference (MD) = -14.10 min, 95% CI -18.46 to -9.74) and increase the time to the next hypertensive crisis (MD = 3.10 h, 95% CI 2.35 to 3.85) compared to nifedipine alone (1 trial, 349 women; low certainty).
    BJOG, 2025 · checked 2026-10-07
35. ev-gtpg-04 · randomized controlled trial
    After exclusion, 404 patients were randomly assigned into EGCG and placebo study groups and subsequently administered either 500 mg of EGCG or placebo, respectively, on a daily basis until full term.
    J Hum Nutr Diet, 2017 · checked 2026-10-07
36. ev-gtpg-09 · case-control study
    Compared with women who did not drink tea during the periconceptional period (487 cases and 688 controls), women who drank tea daily (20 cases and 9 controls) had a 3-fold increased risk (odds ratio = 3.1 [95% confidence interval = 1.4-7.0]) of having an NTD-affected pregnancy.
    Epidemiology, 2011 · checked 2026-10-07
37. ev-gtpg-12 · open-label clinical study
    During the intervention with EGCG, folate levels remained in the normal range in all subjects.
    Clin Transl Sci, 2025 · checked 2026-10-07
38. ev-gtwl-05 · meta-analysis of RCTs
    GT supplementation significantly decreases body weight (WMD: -1.23 kg, 95% CI: -2.13 to -0.33, p = 0.007), BMI (WMD: -0.47 kg/m2, 95% CI: -0.87 to -0.07, p = 0.020) and WC (WMD: -3.46 cm, 95% CI: -6.75 to -0.16, p = 0.040).
    Crit Rev Food Sci Nutr, 2024 · checked 2026-10-06
39. ev-gtwl-08 · RCT
    There were no differences in changes in BMI (-0.13 ± 0.11 compared with -0.05 ± 0.11; P = 0.61), total fat mass (-0.30 ± 0.16 compared with -0.12 ± 0.15 kg; P = 0.40), percentage of body fat (-0.15% ± 0.17% compared with -0.15% ± 0.16%; P = 0.99), or BMD (-0.006 ± 0.002 compared with -0.003 ± 0.002 g/cm(2); P = 0.49) over 12 mo between women taking GTE (n = 61) and those taking a placebo (n = 60).
    Journal of Nutrition, 2016, Long-Term Supplementation of Green Tea Extract Does Not Modify Adiposity or Bone Mineral Density in a Randomized Trial of Overweight and Obese Postmenopausal Women · checked 2026-10-06
40. ev-gtwl-14 · meta-analysis of RCTs
    Tea supplements as adjuvant therapy led to greater improvement in body weight (WMD -2.71, 95% CI -4.95 to -0.46, P = 0.02, I2 = 0%), fasting blood glucose (FBG: WMD -0.40, 95% CI -0.59 to -0.20, P < 0.0001, I2 = 0%) and fasting insulin (FINS: WMD -3.40, 95% CI -4.76 to -2.03, P < 0.00001, I2 = 0%) when compared with placebo.
    Front Endocrinol (Lausanne), 2021 · checked 2026-10-06
41. grtea-r7-12 · RCT secondary analysis
    A secondary analysis was conducted using data from the Minnesota Green Tea Trial (N = 1,075), in which participants were randomized to consume high-dose GTE (843 mg/day EGCG) or placebo capsules for 12 months. ... From baseline to months 6 and 9, respectively, mean ALT change was +78.1% and +82.1% in the UGT1A4 (rs6755571) A/C genotype versus +28.0% and +30.1% in the C/C genotype (p < 0.001 and p = 0.004, respectively).
    J Diet Suppl, 2023 · checked 2026-09-29
42. grtea-r7-14 · prospective cohort
    Tea drinkers (men: hazard ratio 0.78, 95% confidence interval 0.69-0.88; women: hazard ratio 0.8, 95% confidence interval 0.77-0.98) and specifically green tea drinkers (men: hazard ratio 0.78, 95% confidence interval 0.69-0.88; women: hazard ratio 0.84, 95% confidence interval 0.74-0.95) had lower incident risk than never/former drinkers.
    Int J Urol, 2019 · checked 2026-09-29
43. grtea-r7-15 · RCT
    This 12-week randomized, double-blinded, parallel-controlled trial was performed among 62 girls with obesity aged 6 to 10 years old. Participants were allocated to take 400 mg/d DGTP (DGTP group, n = 31) or isodose placebo (Control group, n = 31) at random. ... Regarding other biochemical indicators, there were no significant differences in changed values between the two groups. Throughout the trial, no adverse effects were reported in either group.
    Asia Pac J Clin Nutr, 2024 · checked 2026-09-29
44. ev-gtpg-11 · cross-sectional study
    The median of plasma folate concentration was 48.7 nmol/L in women who drank tea while it is 45.2 nmol/L in women who did not drink tea, with no statistical difference.
    Birth Defects Res A Clin Mol Teratol, 2015 · checked 2026-10-07
45. ev-gtwl-01 · Cochrane review of RCTs
    Meta-analysis of six studies conducted outside Japan showed a mean difference (MD) in weight loss of -0.04 kg (95% CI -0.5 to 0.4; P = 0.88; I(2) = 18%; 532 participants).
    Cochrane Database of Systematic Reviews, 2012, CD008650, Green tea for weight loss and weight maintenance in overweight or obese adults · checked 2026-10-06