Green tea extract: what it may do and how to lower the liver risk
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- Standardized green tea extract, taken with food. Best for: Adults whose doctor has okayed an extract. See options on Amazon
- Organic green tea bags. Best for: People who want green tea without a concentrated extract. See options on Amazon
- Lower-dose green tea extract capsules. Best for: Adults who want a smaller amount per capsule. See options on Amazon
What green tea extract is
Green, black and oolong teas all come from Camellia sinensis. The National Center for Complementary and Integrative Health (NCCIH) explains that green tea leaves are steamed, pan fried and dried but not fermented. NIH's LiverTox database says this preserves the antioxidant polyphenols called catechins.
Green tea extract concentrates these compounds into capsules. LiverTox notes it is listed in more than 100 over-the-counter herbal products, including many weight loss formulas, and is not approved for any specific medical use.
What the research shows
| Claim | What NCCIH reports |
|---|---|
| Weight loss | Catechins and caffeine may have a modest effect |
| Cholesterol | Small drops in total and LDL; no change in HDL or triglycerides |
| Cancer prevention | Inconsistent results |
| Heart disease | Lower risk seen in Asian but not Western populations (green tea consumption) |
Weight. NCCIH says the catechins and caffeine in green tea may have a modest effect on body weight, and effects may vary with the product's makeup and how physically active you are.
Cholesterol. In randomized trials, mostly of extract supplements, green tea reduced total and LDL cholesterol to a small extent but did not change HDL or triglycerides.
Other claims. Studies on cancer risk have been inconsistent. The only FDA-approved green tea product is a prescription ointment for genital warts, which is very different from oral capsules.
The liver risk
LiverTox gives green tea extract a likelihood score of A, meaning it is a well-established cause of clinically apparent liver injury.
- Cases. More than 100 cases have been reported, including acute liver failure that required urgent transplant or caused death.
- Timing. Injury typically appears within 1 to 6 months of starting.
- Lab changes. In a large study of postmenopausal women, liver enzyme (ALT) rises occurred in 6.7% taking extract versus 0.7% on placebo.
- Who is more at risk. NCCIH says people with a specific immune gene variant appear especially susceptible; between 5 and 15 percent of Americans carry it.
- Weight loss blends. LiverTox lists several weight loss products containing green tea linked to rare liver injury.
- Beverage vs extract. NCCIH reports no safety concerns for green tea as a beverage in adults, and LiverTox says drinking green tea has not been associated with liver injury, though a few cases followed very large amounts of tea infusions.
LiverTox says most people recover quickly after stopping. Stop and see a doctor right away for yellow skin or eyes or any other sign of liver trouble.
Other side effects and interactions
- Side effects. Nausea, constipation, abdominal discomfort and increased blood pressure. At high doses, headache and dizziness.
- Caffeine. Extracts may contain caffeine; NOW Foods lists up to 4 mg per capsule.
- Nadolol. High doses of green tea reduced blood levels of this beta-blocker.
- Atorvastatin. Green tea extract can lower levels of this cholesterol drug.
- Raloxifene. An NCCIH-funded study found an interaction with this osteoporosis drug.
- Pregnancy and breastfeeding. Keep caffeine moderate and ask your provider.
How to take it more safely
- With food. NOW Foods directs 1 capsule daily with a meal and says not to take it on an empty stomach or exceed the dose.
- Check EGCG per capsule. NOW Foods' extract gives 400 mg standardized to at least 80% catechins and 50% EGCG (200 mg).
- Avoid stacking. Do not combine an extract with weight loss blends that also contain green tea.
- Liver conditions. NOW Foods advises consulting a physician if you have liver impairment.
- Consider the beverage. If you mainly enjoy green tea, brewed tea avoids the concentrated extract.
What to look for when you buy
Standardized green tea extract, taken with food
Best for: Adults whose doctor has okayed an extract
NOW Foods lists 400 mg of extract with at least 50% EGCG per capsule, one daily with a meal, and clear liver cautions.
Watch out: Rare but serious liver injury. Never take on an empty stomach or exceed the label. Stop for liver symptoms.
See options on AmazonOrganic green tea bags
Best for: People who want green tea without a concentrated extract
NCCIH reports no safety concerns for green tea as a beverage in adults.
Watch out: Contains caffeine. Keep intake moderate if pregnant or sensitive to caffeine.
See options on AmazonLower-dose green tea extract capsules
Best for: Adults who want a smaller amount per capsule
Smaller capsules make it easier to stay at or below label amounts.
Watch out: Same liver risk. Avoid stacking with weight loss blends that contain green tea.
See options on AmazonQuestions people ask
- Does green tea extract help you lose weight?
- NCCIH says its catechins and caffeine may have a modest effect on weight, varying by product and activity level.
- Is green tea extract bad for your liver?
- Rarely, but seriously. LiverTox calls it a well-established cause of liver injury, with more than 100 reported cases. Drinking green tea has not been linked to the same risk.
- Does green tea extract have caffeine?
- Often a small amount. NOW Foods lists up to 4 mg of naturally occurring caffeine per capsule.
- Should I take green tea extract with food?
- Yes. NOW Foods says to take it with a meal and never on an empty stomach.
- Can green tea extract interact with medicines?
- Yes. It can lower levels of nadolol and atorvastatin and interacted with raloxifene in a study. Ask your provider.
Sources
- Green Tea: Usefulness and Safety (nccih.nih.gov), National Center for Complementary and Integrative Health
- Green Tea - LiverTox (ncbi.nlm.nih.gov), National Institute of Diabetes and Digestive and Kidney Diseases
- EGCg Green Tea Extract 400 mg Veg Capsules (www.nowfoods.com/products/supplements/egcg-green-tea-extract-400-mg-veg-capsules), NOW Foods