Other than water, tea is the most consumed beverage worldwide. And for good reason: tea is great for you, particularly the green variety.
Several benefits of green tea are supported by solid research. Others, much less so. For example, influencers sometimes gush about green tea being “nature’s Ozempic,” suggesting it’s as effective as obesity medication. If this claim sounds exaggerated, that’s because it is, researchers say.
Below, they explain what the science shows about green tea’s role in countering obesity and diabetes, boosting heart and brain health, and fighting cancer.
Green tea, a nutrition unicorn
Tea leaves are unique because they have more catechins than any other drink or food. These compounds protect cells from damage as we get older.
Green tea may be especially healthy compared to other teas, partly because it undergoes little processing on the way to our cups. Black and oolong teas are fermented, a process that reduces their catechins, although fermentation does yield other kinds of healthy compounds.
Green tea contains a few types of catechins, but one called EGCG is the most powerful for safeguarding the cells and fighting inflammation. “That’s what makes green tea so special,” says Laura Acosta, an instructional associate professor of nutrition at the University of Florida who researches green tea.
How to drink it
When green tea is freshly brewed, it packs more EGCG than ready-to-mix or ground green tea powders, which range widely in their EGCG content, from 2 to 200 mg per serving, Acosta says. If you do go the powder route, look for packages that state their EGCG content, she adds, and try to consume them quickly after buying. Sitting on pantry shelves for six months, powders lose 30-50% of their catechins, Acosta says, meaning fewer health benefits.
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Aim for 2 to 4 cups of green tea per day, says Jeffrey Blumberg, a research professor of nutrition science at Tufts University, depending on your sensitivity to caffeine. “Data suggest there are diminishing returns for health after five cups,” says Marilyn Cornelis, associate professor of preventive medicine at Northwestern University. “More isn’t necessarily adverse,” but the benefits start to plateau.
You’ll want to maintain this intake for a while—years, not days. “Over time, it will have a cumulative effect,” Acosta says.
Managing obesity
So, are TikTokers right that you can swap obesity medications like Ozempic for a tall cup of tea?
Don’t count on it. The research isn’t as clear as social media suggests. For example, an influencer dietitian TikTok post in March analyzed one clinical trial on whether green tea acts like obesity medications by triggering the hormone GLP-1, which promotes feelings of fullness and lower blood sugar. According to her, the outcome of the trial was that green tea did elevate GLP-1—but the actual result “isn’t what she implied,” Blumberg says. In truth, the researchers found no significant difference between the group that got the green tea, and the group that didn’t.
A 2017 research review found no evidence that green tea affects blood glucose levels. However, Cornelis thinks it could “inhibit the absorption of carbohydrates, which may reduce glucose levels.” Other studies found that green tea’s catechins contributed to feelings of fullness and drove weight loss. “In theory, it could help with managing obesity or diabetes, but we need a lot more data to support it,” says Dr. Sara Ghoneim, a gastroenterologist at Massachusetts General Hospital and spokesperson for the American Gastroenterological Association.
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Clinical research on green tea typically involves very high doses of EGCG, using pills instead of the drink. These “green tea extract” pills are available online, packing as many as 800 mg of EGCG. The drink won’t provide that much unless you dust off your beer hat from college and slurp it all day.
Very high doses may damage the liver if taken regularly over many years, but research suggests that only about 5% of people are particularly vulnerable to these effects. “Basic research in animals suggests that high doses can harm the liver,” but perhaps only while fasting from food, when the liver is more vulnerable, Blumberg says.
However, the extract may leave out some of the beneficial properties of tea. “I encourage the whole beverage,” Cornelis says. Excess green tea consumption may also cause nausea or acid reflux, Ghoneim notes, especially for those who are sensitive to tea. “It’s really individual dependent,” she says. “Start with a couple of cups and see how you do.”
The effects of drinking a few cups per day would be very gradual, like a single pound lost over 12 weeks. “Eating tea plants is not like a drug. It won’t have an overwhelming effect,” says Carol Johnston, professor of nutrition at Arizona State University. But that’s no reason to put down your cup, she adds. “A slow, moderate weight loss is the healthiest kind of weight loss. Don’t expect to lose 10 pounds in two weeks. This is a lifelong process.”
Preventing heart disease
Regularly drinking green tea supports heart health, partly by decreasing blood pressure, according to a recent meta-analysis. Other research, co-authored by Acosta, showed a similar effect in postmenopausal women.
It could lower cholesterol as well, Cornelis found. “It reduced bad cholesterol and increased good cholesterol,” she says. “That may underlie the beneficial impact on cardiovascular disease.”
Animal studies point to similar benefits, though Johnston notes that most research in humans suggests that only 5% of green tea’s catechins actually get into the blood system. “It’s poorly absorbed,” she says. But there’s a potential solution: mix green tea with sources of vitamin C, like lemon juice or blended strawberries, which act synergistically with the tea. “Vitamin C can enhance some of the absorption,” Johnston says.
Protecting brain health
Drinking green tea is associated with a lower risk of Alzheimer’s and Parkinson’s disease. Brain health is one of the “best established health benefits” of green tea, Acosta says.
The caffeine in tea may be especially helpful in keeping the mind sharp. Plenty of research shows that caffeine boosts cognition in the short term, which may translate into long-term protection for frequent quaffers, Cornelis says. Caffeine blocks certain receptors in the brain that affect dopamine, which is involved in Parkinson’s, she adds.
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Now, a sensitive topic: green tea vs. coffee. Both drinks have their passionate defenders, but it’s tough to pick a clear winner. Coffee has twice as much caffeine as tea, but green tea has more L-theanine, a building block of protein that has a calming effect and improves focus and attention, Blumberg says. At least one study has found that green tea, but not coffee, was associated with better cognition as people age.
Detoxing
Another theory popping up on the internet is that green tea “detoxifies” the body. This idea isn’t accurate, Acosta says, because EGCG can actually become a toxin in its own right. After EGCG spurs healthy adaptations, the body works to transform and eliminate this compound to avoid being harmed by it. “Green tea is a powerful antioxidant,” Acosta says, “but detoxification is completely different.”
Fighting cancer
People on social media have made bold statements about green tea’s ability to combat cancer. What does the research actually show?
In 2021, a large review found little evidence for green tea’s role in preventing cancer. However, lab research suggests that EGCG blocks pathways involved in tumor formation, says Dr. James Segars, a cancer researcher and head of the reproductive endocrinology unit at Johns Hopkins.
Other research shows an association between green tea and a lower risk of certain cancers such as breast, ovarian, prostate, and neck. “It might be protective,” Acosta says, as part of a healthy overall lifestyle. Segars studies cells to see how green tea could reduce the size of fibroids, abnormal masses of tissue that may develop into uterine cancer. He tells patients with a family history of fibroids to take two tablets of 400 mg of green tea extract, daily.
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In theory, green tea may even help with treating cancer, partly because high doses seem to promote the death of cancerous cells. More research is needed on these effects, Segars says. Dr. Mary E. Money, an internal medicine physician, was diagnosed with advanced ovarian cancer in 2012. Several years later, she was impressed by studies on green tea and cancer, and began sipping 6 to 8 mugs of the beverage throughout the day, instead of taking extract pills—without changing the rest of her regimen. Her cancer biomarkers improved significantly, she says. Money continues to receive chemotherapy when needed; green tea may act synergistically with chemotherapy in some cases, research suggests.
However, the evidence is mixed, with other studies showing that antioxidants, including those found in tea, might interfere with certain cancer treatments, such as chemotherapy and radiation therapy.
Money notes that her experience is just that: one anecdote. She could be a super responder, while others’ responses depend on numerous factors, including their specific diagnosis, treatment strategy, and overall nutrition. “There are so many variables,” she says. What’s clear is that—big picture—green tea is a healthy choice.
