"Higher concentrations of green tea extract can be really dangerous, because it can potentially cause serious liver damage. Plus, the herb itself has been found to alter the effectiveness of a long list of drugs, including certain anti-depressants and anti-clotting medications," said Jeneen Interlandi with Consumer Reports.
It can also elevate your heart rate and blood pressure, and researchers suggest that up to 10 percent of people who suffer acute liver failure from green tea extract could die as a result. Consumer Reports put green tea extract powder on its list of 15 supplement ingredients to avoid.
"The manufacturers who make these supplements are not required to prove to federal regulators that their products are safe, that they're effective or even that they're accurately labeled, so you really don't know what you're buying," said Interlandi.
Studies have also found that, even in high doses, green tea probably won't help you lose weight.
"It's true that green tea can raise your metabolic rate, so you burn more calories, but that's probably just due to its caffeine and catechins it contains. Catechins are antioxidants that are found in green tea," said Interlandi.
She said most people can reap the health benefits of green tea with just a few cups a day.
For the full list of the 15 supplement ingredients Consumer Reports says to avoid, CLICK HERE.