EGCG Side Effects
Green Tea Extract Users Beware!

EGCG side effects are seldom observed during human trials. Nevertheless, if you are consuming green tea extract, it is important to pay attention to the quality of your brand.

EGCG (epigallocatechin gallate) is usually well tolerated during human trials. It is water-soluble, which means that if you overdose, it is unlikely to build up. The excess simply gets flushed out of your body.

The article discusses the major side effects of pure EGCG. If your green tea extract contains caffeine, please refer to the full list included in my green tea side effects article.

EGCG Side Effect #1:
Neural Tube Defect

Drinking a large amount of green tea has been linked to neural tube birth defect in babies.

A 2005 study conducted by University of Murcia in Spain and John Innes Centre in England discovered that EGCG inhibits an enzyme called dihydrofolate reductase (DHFR). While this reduces your cancer risk, it is actually bad for pregnant mothers because low levels of DHFR can induce folic acid deficiency, causing abnormal neural tube development.

You many want to avoid green tea or EGCG altogether during pregnancy.

EGCG Side Effect #2:
Indigestion and Nausea

Some people may find that consuming EGCG can cause nausea or stomach upset. A study conducted in 1984 found that although tea stimulates the production of gastric acid, sometimes leading to stomach upset, its effects can be mitigated by the addition of milk and sugar to the beverage.

EGCG Side Effect #3:
Having Too Much

There is no recommended daily allowance for EGCG. However, alarm bells have been ringing as scientific studies have linked consuming too much green tea extract with liver toxicity and liver/kidney damage.

What's important to know from these case reports is that taking tea extract is not the same as drinking green tea.

When you take tea extract, you are less likely to know what goes into the leaves (they probably taste bad, that's why they are used for making extract). The tea leaves may be contaminated by herbicide or lead. The manufacturing process might have added other ingredients on top (such as chemical solvent residue, etc).

Green Tea Supplement Side Effects

This means that you should only buy green tea extract from quality brands and restrict your tea program to, say, 3 months at a time, switching over to brewed tea for long term consumption.

Drinking green tea is generally very beneficial for your health! Follow common sense guidelines, and seek advice from your health care provider if you have any concerns about how tea may affect your health.

Further information on how to choose an EGCG extract can be found through the link below.


Dubey P, Sundram KR, Nundy S (1984). Effect of tea on gastric acid secretion. Digestive diseases and sciences. 1984 Mar; 29(3):202-6.

Joshua D. Lambert, Shengmin Sang, and Chung S. Yang (2007). Possible Controversy over Dietary Polyphenols: Benefits vs Risks. Chem. Res. Toxicol., 20 (4), 583 -585, 2007. 10.1021/tx7000515 S0893-228x(70)00051-6.

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