While green tea is a popular beverage, green tea extract can be put into concentrate or pill form as a dietary supplement, such as Exolise. Green tea, unlike other teas, are unfermented, which helps preserve the antioxidant polyphenolic catechols found in the tea. It is a popular belief that the antioxidant activity can:
- Improve general health,
- Prevent cancer and heart disease,
- Decrease serum lipid levels,
- Promote weight loss,
- Decrease periodontal disease, and
- Treat clostridial diarrhea
However, the FDA has not approved green tea extract for any specific medical use and there is even evidence that green tea extract can do more harm than good.
Toxicity and Adverse Effects
If too much green tea extract is ingested, it can become toxic and even cause liver damage and failure. Usually, symptoms of toxicity are relatively mild. These symptoms include:
- Headache,
- Dizziness, and
- Nausea
However, there have now been more than one hundred cases of liver injury that have been linked to the consumption of green tea extract dietary supplements. Symptoms of liver injury in these cases appeared between 1 to 6 months after the individual started using the dietary supplement. The liver injury present was an acute hepatitis-like syndrome with a hepatocellular pattern of serum enzyme elevation. In some of these cases, the liver injury led to liver failure causing death.
Safety
Even though new research suggests that green tea extract can cause liver injury, it is still not regulated in terms of safety by the FDA. Cases of green tea toxicity are extremely rare and very unlikely from simply drinking tea. The chance of toxicity increases when the green tea is made in concentrates, like those in dietary supplements. The maximum tolerated dose of green tea extract in humans was found to be 9.9g per day, which is equivalent to about 24 cups of green tea.
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