In experiments over fruit flies, the team from University of California-Irvine discovered that excessive consumption adversely affected development and reproduction in fruit fly populations.
According to them, one should avoid high dose of green tea or any natural product as nutraceuticals such as green tea, while growing in popularity, are largely unregulated.
"While green tea could have health benefits at low doses, our study and others have shown that at high doses, it may have adverse effects," said Mahtab Jafari, associate professor of pharmaceutical sciences.
"Further work is needed to make any definite recommendations but we suggest that green tea should be consumed in moderation," she added.
For the study, Ms Jafari and colleagues investigated the effects of green tea toxicity on the development and reproduction in fruit fly Drosophila melanogaster.
Embryos and larvae were subjected to various doses of green tea polyphenols.
Larvae exposed to 10 milligrams of green tea were slower to develop, were born smaller and exhibited a dramatic decline in the number of emerged offspring.
Ten milligrams of green tea made the flies more susceptible to starvation and heat stress but protected them against dehydration.
Female offspring showed decreased reproductive output and a 17 per cent reduction in lifespan while males were unaffected, the study found.
Ten milligrams of green tea caused morphological abnormalities in reproductive organs such as testicular and ovarian atrophy.
Ms Jafari believes that high doses of green tea may cause "too much" apoptosis or cell death.
Derived from the plant Camellia sinensis, green tea is popular worldwide for its purported brain and heart health and anti-cancer properties.
Ms Jafari noted that in other tests with mice and dogs, green tea compounds in large amounts dramatically reduced body weight and, in mice, negatively affected embryo development.
"We are planning to measure total consumption and identify and quantify the metabolites of natural products in flies," Ms Jafari pointed out, adding that these experiments will enable us to have a better understanding of toxic doses in humans.
The paper appeared in the Journal of Functional Foods.
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