Green tea extract (EGCG) C
The effect is small; there is a risk of rare but severe liver injury
Citable fact
«Green tea extract (EGCG)» — evidence level C. Dosage: 300–500 mg of EGCG per day (usually 500–1000 mg of green tea extract) together with 200–300 mg of caffeine. Doses above 800 mg of EGCG per day increase the risk of liver damage. Source: PMID 27883924, permanent link to the source in the list below.
How it works
EGCG is the main catechin of green tea. It inhibits the enzyme catechol-O-methyltransferase, so norepinephrine is broken down more slowly, and it prolongs its action on beta-adrenergic receptors of adipose tissue. This enhances lipolysis and fat oxidation. In addition, catechins and the caffeine naturally present in tea act synergistically, increasing resting energy expenditure. It is caffeine that largely determines the observed effect.
Dosage and intake
300–500 mg of EGCG per day (usually 500–1000 mg of green tea extract) together with 200–300 mg of caffeine. Doses above 800 mg of EGCG per day increase the risk of liver damage
With food, usually before training or in divided doses. Taking it on an empty stomach increases the risk of liver damage and stomach discomfort
Forms
Green tea extract capsules with a standardized EGCG content or the ordinary beverage. In tea the catechin doses are lower than in concentrated extracts, and the link with liver damage has been described specifically for extracts
What is confirmed
- A small increase in resting energy expenditure and fat oxidation
- Contains antioxidant catechins
- In combination with caffeine it may support attention and performance
Adverse effects and limitations
- MANDATORY WARNING: cases of severe liver damage, up to acute liver failure and transplantation, have been described with concentrated green tea extracts. The risk is rare but serious, and is linked primarily to EGCG doses above 800 mg per day and to intake on an empty stomach
- The effect on fat mass is small and is largely explained by the caffeine in the complexes
- May increase liver enzyme activity; if jaundice, dark urine and pain in the right upper abdomen appear, intake is stopped immediately
- Reduces iron absorption, especially when taken with plant food; rarely causes GI upset and insomnia
Interactions
- With iron and iron preparations — reduced absorption; separate the times of intake
- With drugs metabolized via CYP3A4 — their concentrations may change
- With caffeine, other stimulants and hepatotoxic drugs — additive load and risks
Who must not use it
- Under 18 years: Concentrated extracts are not recommended for children and adolescents
- Pregnancy and lactation: High doses of catechins and extracts are not recommended in pregnancy and lactation; ordinary tea in moderate amounts is acceptable
- Liver disease and elevated liver enzymes — contraindicated
- Iron deficiency anemia — caution because of reduced iron absorption
- Use of hepatotoxic drugs — contraindicated
- Hypertension and arrhythmias — caution, especially in complexes with caffeine
- Driving with increased sensitivity to caffeine — a limitation
Sources
- Physiological effects of epigallocatechin-3-gallate (EGCG) on energy expenditure for prospective fat oxidation in humans: A systematic review and meta-analysis · Kapoor MP, Sugita M, Fukuzawa Y · The Journal of nutritional biochemistry, 2017 · PMID 27883924
- Current Evidence to Propose Different Food Supplements for Weight Loss: A Comprehensive Review · Watanabe M, Risi R, Masi D · Nutrients, 2020 · PMID 32962190
See also
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