Green Tea Extract and EGCG: Benefits, Caffeine and Safety

EGCG (epigallocatechin gallate) is the main catechin in green tea, and green tea extract is a concentrated form of it. Studies of green tea extract have measured body weight and cholesterol. At high doses, especially on an empty stomach, it can raise liver enzymes, so the amount of EGCG per serving and taking it with food matter. This guide covers what EGCG is, what the research shows, how much caffeine green tea extract has, side effects and liver safety, and how to choose one.

It is educational, not medical advice.

Key Takeaways

• Weight: a Cochrane review looked at green tea preparations and body weight in overweight or obese adults (Jurgens et al., 2012).
• Cholesterol: across 14 trials, green tea or its extract lowered total cholesterol by 7.20 mg/dL and LDL cholesterol by 2.19 mg/dL (Zheng et al., 2011).
• Liver safety: 800 mg or more of EGCG a day from supplements raised liver enzymes in clinical trials (EFSA, 2018).
• Take it with food: on an empty stomach, peak blood levels of free EGCG were more than 3.5 times higher than with food (Chow et al., 2005).

What Is EGCG?

Green tea is made from the leaves of the tea plant, Camellia sinensis, without fermentation, which keeps its polyphenols from oxidizing. Most of the polyphenols in green tea are catechins, and EGCG, short for (-)-epigallocatechin-3-gallate, is the most important of them (EFSA, 2018).

Green tea also contains caffeine and the amino acid L-theanine, which is why tea feels different from coffee to many people. Our Theanine Nasal Spray provides L-theanine as a spray absorbed through the lining of the nose.

Green Tea Extract vs Green Tea

Green tea extract concentrates the catechins from the leaves into a capsule or powder. That makes the dose much more variable than with a cup of tea. In Europe, green tea drinkers get on average 90 to 300 mg of EGCG a day from tea, and heavy drinkers up to 866 mg, while green tea supplements provide anywhere from 5 to 1,000 mg of EGCG a day (EFSA, 2018).

How it is taken also matters. A review of 159 human studies found that liver side effects came from a limited range of concentrated green tea preparations taken as large single doses, not from brewed tea or extracts taken in drinks or with food (Hu et al., 2018).

What the Research Shows

Green tea extract and weight

• Cochrane review: in trials of 12 to 13 weeks, six studies outside Japan showed an average weight difference of 0.04 kg, and eight studies in Japan showed differences of 0.2 to 3.5 kg in favour of green tea preparations. The authors concluded the weight loss was small, statistically non-significant and not likely to be clinically important (Jurgens et al., 2012).
• Earlier meta-analysis: across 11 studies, catechins, or an EGCG and caffeine mix, led to about 1.31 kg more weight lost than control. The effect looked smaller in people who already had more than 300 mg of caffeine a day, though that difference was not statistically significant (Hursel et al., 2009).

OEA, a different ingredient studied for appetite, is covered in OEA (oleoylethanolamide): benefits, dosage and safety.

Green tea extract and cholesterol

A meta-analysis of 14 randomized trials with 1,136 people found that green tea drinks or extracts lowered total cholesterol by 7.20 mg/dL and LDL cholesterol by 2.19 mg/dL, with no change in HDL cholesterol (Zheng et al., 2011).

To see how green tea compares with coffee, protein and strength training for metabolism, read our guide on how to boost metabolism naturally.

Does Green Tea Extract Have Caffeine?

Often, yes, but it depends on the product. Brewed white, green and black teas tested in one study had 14 to 61 mg of caffeine per 6 or 8 oz serving, and decaffeinated teas had less than 12 mg (Chin et al., 2008). Extracts vary much more, and decaffeinated green tea extracts are sold, so check the label for caffeine per serving. How caffeine compares with gentler stimulants is covered in theobromine vs caffeine.

Green Tea Extract Side Effects and Liver Safety

Most people in trials tolerated green tea extract well, but high doses can affect the liver:

• Liver enzymes: in a one-year trial of 1,075 postmenopausal women taking extract with 843 mg of EGCG a day, 6.7 percent had a rise in the liver enzyme ALT, compared with 0.7 percent on placebo; nausea was also more common (Dostal et al., 2015). ALT went back to normal after stopping and rose again when the extract was restarted (Yu et al., 2017).
• The 800 mg line: the European Food Safety Authority found that 800 mg or more of EGCG a day from supplements raised liver enzymes in clinical trials, and could not identify an EGCG dose from extracts that could be considered safe (EFSA, 2018).
• Empty stomach: green tea extract taken on an empty stomach is more likely to cause side effects than taken with food (Sarma et al., 2008). In one study, mild nausea was most common at the highest dose and when fasting (Chow et al., 2005).
• Rare reactions to tea: rare cases of liver injury have also been reported after drinking green tea, most probably an individual reaction (EFSA, 2018).

The US Pharmacopeia asks green tea extract labels to say: do not take on an empty stomach, take with food, do not use if you have a liver problem, and stop and see a healthcare practitioner if you develop signs of liver trouble such as abdominal pain, dark urine or yellowing of the skin or eyes (Oketch-Rabah et al., 2020).

Can Green Tea Interact With Medicines?

Yes. In 10 healthy volunteers, drinking 700 mL of green tea a day for 14 days lowered blood levels of the blood pressure medicine nadolol by about 85 percent and weakened its effect on blood pressure (Misaka et al., 2014). If you take prescription medicines, check with your pharmacist or clinician before taking green tea extract.

How Much EGCG Per Day?

There is no official daily amount. One systematic review derived a safe intake of 338 mg of EGCG a day for adults when taken as a solid dose, such as a capsule, and an observed safe level of 704 mg a day in drink form (Hu et al., 2018). EFSA linked 800 mg a day or more from supplements to raised liver enzymes (EFSA, 2018). Follow the label, add up the EGCG from every product you take, and take it with food.

How to Choose a Green Tea Extract

• EGCG per serving: look for the amount of EGCG, not just the amount of extract.
• Caffeine: check whether it is listed, especially if you drink coffee or take it later in the day.
• Directions: choose a product whose label says to take it with food.
• Quality: look for third-party tested ingredients.

Green Tea Extract in Our OEA Supplement

Our OEA Supplement gives 200 mg each of OEA, palmitoylethanolamide (PEA), L-theanine, acetyl-L-carnitine (ALCAR) and green tea extract per two-capsule serving, with ginger extract and vegan capsules. The label suggests two capsules daily, 15 to 30 minutes before your largest meal, and its green tea extract contains some caffeine. More about OEA is on our OEA ingredient page, and related guides are in our metabolic health and energy balance guide and Learn hub.

Safety note: people with a liver condition, those who are pregnant or breastfeeding, and anyone taking prescription medicines should talk with a clinician before taking green tea extract.

Sources

• Jurgens TM et al. Green tea for weight loss and weight maintenance in overweight or obese adults. The Cochrane Database of Systematic Reviews, 2012. PubMed
• Zheng XX et al. Green tea intake lowers fasting serum total and LDL cholesterol in adults: a meta-analysis of 14 randomized controlled trials. The American Journal of Clinical Nutrition, 2011. PubMed
• EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS). Scientific opinion on the safety of green tea catechins. EFSA Journal, 2018. PubMed
• Chow HH et al. Effects of dosing condition on the oral bioavailability of green tea catechins after single-dose administration of Polyphenon E in healthy individuals. Clinical Cancer Research, 2005. PubMed
• Hu J et al. The safety of green tea and green tea extract consumption in adults: Results of a systematic review. Regulatory Toxicology and Pharmacology, 2018. PubMed
• Hursel R et al. The effects of green tea on weight loss and weight maintenance: a meta-analysis. International Journal of Obesity, 2009. PubMed
• Chin JM et al. Caffeine content of brewed teas. Journal of Analytical Toxicology, 2008. PubMed
• Dostal AM et al. The safety of green tea extract supplementation in postmenopausal women at risk for breast cancer: results of the Minnesota Green Tea Trial. Food and Chemical Toxicology, 2015. PubMed
• Yu Z et al. Effect of Green Tea Supplements on Liver Enzyme Elevation: Results from a Randomized Intervention Study in the United States. Cancer Prevention Research, 2017. PubMed
• Sarma DN et al. Safety of green tea extracts : a systematic review by the US Pharmacopeia. Drug Safety, 2008. PubMed
• Oketch-Rabah HA et al. United States Pharmacopeia (USP) comprehensive review of the hepatotoxicity of green tea extracts. Toxicology Reports, 2020. PubMed
• Misaka S et al. Green tea ingestion greatly reduces plasma concentrations of nadolol in healthy subjects. Clinical Pharmacology and Therapeutics, 2014. PubMed

Frequently Asked Questions

What is EGCG?

Epigallocatechin gallate, the main catechin in green tea and the compound most green tea extracts are measured by.

Is green tea extract the same as green tea?

No. The extract concentrates the catechins, so one serving can hold far more EGCG than a cup of tea.

Does green tea extract have caffeine?

Many do, but amounts vary and decaffeinated extracts exist. Check the label for caffeine per serving.

Is green tea extract good for weight loss?

Trials of about 12 weeks have measured body weight in overweight or obese adults taking green tea preparations.

Is green tea extract safe for your liver?

At high doses it can raise liver enzymes. EFSA linked 800 mg or more of EGCG a day from supplements to raised liver enzymes. Take it with food and stop if you notice signs of liver trouble.

How much EGCG per day is safe?

There is no official figure. One review derived 338 mg a day as a safe intake from capsules or tablets.

Should I take green tea extract with food?

Yes. Taking it on an empty stomach raises blood levels of EGCG and makes side effects more likely.

Can green tea interact with medications?

Yes. Green tea lowered blood levels of the blood pressure medicine nadolol by about 85 percent in one study. Ask your pharmacist if you take prescription medicines.

These statements have not been evaluated by the Food and Drug Administration. This content is for education and is not medical advice. Our products are not intended to diagnose, treat, cure or prevent any disease. Talk with a healthcare provider before starting a new supplement if you are pregnant, breastfeeding or taking medication.