Even though there always seems to be a new trendy wellness tonic people are talking about (golden milk! CBD sparkling water!), nothing has withstood the test of time quite like green tea.

One of the most popular teas in the world, it’s accessible virtually no matter where you are. But don’t call it basic. There’s a very good reason why everyone from wellness influencers, doctors, and nutrition experts love it—including registered dietitian and nutritionist Maya Feller, RDN. “In my opinion, having a cup of green tea is great!” she says. Green tea (and all the antioxidants it contains) offers all kinds of cancer-fighting, bloat-reducing, metabolism-boosting benefits.

But some people claim a cup of tea isn’t the only way to get those perks. Green tea extract—which contains the concentrated antioxidants, polyphenols, vitamins, and flavonoids of green tea—is available in capsule form, too. But here’s what you should know before adding it to your supplement routine.

What are the potential green tea extract benefits?

One thing green tea extract likely cannot do? Promote weight loss—most human trials show only a small (and not often significant) effect on body weight. It also likely cannot help with exercise performance (research is very mixed on this front), despite claims to the contrary. Yet it remains a very common ingredient in diet pills and other supplements.

However, green tea extract does have some potential benefits, including the following:

1. It could help with cognitive function. Feller credits several components of green tea extract for potential brain-boosting powers. One of the biggies: antioxidants, which have been linked to improving longterm brain health. (It’s likely not a coincidence that in Okinawa, a notorious Blue Zone known for its long lifespans, green tea is consumed every day.) Feller says getting the antioxidants in the form of a green tea extract capsule is another possible way to benefit.

2. It could help protect against fatty liver disease. Green tea extract has been linked in a small study to improved symptoms of fatty liver disease. One likely reason why: The high levels of antioxidants and EGCGs (aka epigallocatechin gallate, a catechin that’s been linked to improved heart health and blood sugar levels).

3. It might help your heart. The catechins in green tea may be anti-hypertensive, meaning they could help reduce blood pressure. The high antioxidant levels—which again, are also readily available in green tea extract as well as the tea—likely also play a role in reducing oxidative stress. However, it should be noted that many studies in this space were performed on mice, not humans, so more research needs to be done before anything is conclusive here.

4. It may be good for your hair. Green tea extract’s benefits may extend to haircare, too. It’s been linked to keeping locks from getting greasy in a very, very small study. (So again, take this one with a grain of salt.)

Are there any risks or downsides to green tea extract?

Green tea extract may come with some serious side effects if taken in high doses. A 2017 review of studies notes that green tea extract has been associated with liver damage and even liver failure (and it’s something Feller cautions against, too.) According to the American College of Gastroenterology, this risk  is likely due to the excessively high amount of catechins in green tea extract (as much as 700 mg per pill, compared to the 50-150 mg you’d get in a cup of regular green tea). This is a rare side effect, but serious enough that the Canadian federal government set new labeling guidelines in 2017 specifically requiring companies in that country to more clearly disclose the liver-related risks of green tea extract. Other potential side effects include constipation, nausea, and abdominal discomfort.

Most capsules also have a low amount of caffeine, Feller adds, so it might affect sleep rhythms of people who are caffeine sensitive (especially if a person is drinking other forms of caffeine on top of the extract.) As with any supplement, Feller says green tea extract may interact with other medications or supplements you may be taking, so definitely consult with your practitioner before adding it into your routine.

The bottom line: Green tea extract has limited benefits and some pretty serious potential side effects. “I would suggest that people exercise caution and seek out guidance from a qualified health care provider when using a pharmacological dose of a supplement like this,” says Feller. Or just stick with regular green tea, which is generally a pretty safe bet.

Matcha—a highly concentrated type of green tea—is even popping up at happy hour, in beer and cocktails.