ABOUTAfter water, tea is the most consumed beverage in the world. And for good reason: tea is very good for you, especially green tea.
Some of green tea’s benefits are backed by solid research. Others, much less so. For example, influencers sometimes rave about green tea being “nature’s Ozempic,” suggesting it’s as effective as an obesity drug. If that sounds like an exaggeration, that’s because it is, researchers say.
Below, they explain what science shows about green tea's role in fighting obesity and diabetes, promoting heart and brain health, and fighting cancer.
Green tea is a unicorn in nutrition
Tea leaves are unique because they contain more catechins than any other drink or food. These compounds protect cells from damage as we age.
Green tea may be especially beneficial compared to other teas, in part because it undergoes little processing on its way to our cups. Black and oolong teas are fermented, a process that reduces their catechins, although fermentation produces other kinds of beneficial compounds.
Green tea contains several types of catechins, but one, called EGCG, is the most powerful for protecting cells and fighting inflammation. “That’s what makes green tea so special,” says Laura Acosta, an assistant professor of nutrition at the University of Florida who studies green tea.
How to drink
When freshly brewed, green tea contains more EGCG than ready-to-blend or ground green tea powders, which vary widely in EGCG content, from 2 to 200 mg per serving, says Acosta. If you do go the powder route, look for packages that list the EGCG content, she adds, and try to consume them quickly after purchase. After sitting on pantry shelves for six months, powders lose 30 to 50 percent of their catechins, says Acosta, meaning fewer health benefits.
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Aim for two to four cups of green tea a day, depending on your sensitivity to caffeine, says Jeffrey Blumberg, a research professor of nutritional science at Tufts University. “The evidence suggests that after five cups, there’s a decline in health,” says Marilyn Cornelis, an assistant professor of preventive medicine at Northwestern University. “More than that isn’t necessarily harmful,” but the benefits start to wane.
You'll need to maintain this routine for a while—years, not days. “Over time, it's going to have a cumulative effect,” Acosta says.
Fight against obesity
So, are TikTokers right when they say that obesity drugs like Ozempic can be swapped for a large cup of tea?
Don't count on it. The research isn't as clear-cut as social media suggests. For example, an influential nutritionist TikTok post analyzed in March one clinical trial about whether green tea acts as an anti-obesity drug by activating the hormone GLP-1, which makes you feel full and lowers blood sugar. She says the study found that green tea did increase GLP-1 levels, but the actual result “wasn’t what she was implying,” says Blumberg. In fact, the researchers found no significant difference between the group that got green tea and the group that didn’t.
A 2017 research review found no evidence that green tea affects blood glucose levels. However, Cornelis believes that it may “inhibit the absorption of carbohydrates, which may lower glucose levels.” Other studies have shown that green tea catechins contributed to a feeling of satiety and resulted in weight loss“Theoretically, it could help fight obesity or diabetes, but we need a lot more data to confirm that,” says Dr. Sarah Ghoneim, a gastroenterologist at Massachusetts General Hospital and a spokesperson for the American Gastroenterological Association.
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Clinical studies of green tea typically involve very high doses of EGCG, using pills instead of the drink. These “green tea extract” pills are available online and contain up to 800 mg of EGCG. The drink won’t give you that much, unless you dust off your college beer hat and sip it all day.
Very high doses can 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 animal studies show that high doses can cause liver damage,” but perhaps only during fasting, when the liver is more vulnerable, says Blumberg.
However, the extract may not contain some of the tea’s health benefits. “I recommend drinking the whole thing,” says Cornelis. Drinking too much green tea can also cause nausea or acid reflux, notes Ghoneim, especially in those who are sensitive to tea. “It’s really individual,” she says. “Start with a couple cups and see how it goes for you.”
The effects of drinking several cups a day will be very gradual, like losing a pound over 12 weeks. “Drinking tea plants is not like a drug. It’s not going to have an overwhelming effect,” says Carol Johnston, a professor of nutrition at Arizona State University. But that’s no reason to give up a cup, she adds. “Slow, moderate weight loss is the healthiest kind of weight loss. Don’t expect to lose 10 pounds in two weeks. It’s a lifelong process.”
Prevention of heart disease
Regular green tea consumption may support heart health, in part by lowering blood pressure, according to a new study. meta-analysis. Another researchco-authored by Acosta, showed a similar effect in postmenopausal women.
Cornelis, it can also lower cholesterol. found“It lowered bad cholesterol and raised good cholesterol,” she says. “That may underlie the beneficial effects on cardiovascular disease.”
Animal studies point to similar benefits, though Johnston notes that most human studies show that only 5 percent of green tea’s catechins actually make it into the bloodstream. “It’s not well absorbed,” she says. But there’s a potential solution: Mix green tea with sources of vitamin C, like lemon juice or crushed strawberries, which act synergistically with the tea. “Vitamin C can improve some of the absorption,” Johnston says.
Protecting Brain Health
Drinking green tea has been linked to a lower risk of Alzheimer's and Parkinson's disease. Brain health is one of the “most well-known health benefits” of green tea, Acosta says.
The caffeine in tea may be especially helpful for keeping your mind sharp. Numerous studies show that caffeine boosts cognition in the short term, which may translate into long-term protection for frequent drinkers, Cornelis says. Caffeine blocks certain receptors in the brain that affect dopamine, which is involved in Parkinson's disease, she adds.
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Now comes the delicate subject: green tea versus coffee. Both drinks have their ardent defenders, but it's hard to pick a clear winner. Coffee has twice as much caffeine as tea, but green tea has more L-theanine, a protein building block that has a calming effect and improves focus and attention, says Bloomberg. At least one study found that green tea, but not coffee, was associated with improved cognitive performance in people as they aged.
Detoxification
Another theory floating around the internet is that green tea “detoxifies” the body. That idea is incorrect, says Acosta, because EGCG can actually be a toxin in and of itself. After EGCG stimulates healthy adaptations, the body works to convert and eliminate the compound to avoid causing harm. “Green tea is a powerful antioxidant,” says Acosta, “but detoxification is a completely different thing.”
Fighting cancer
People on social media did bold statements about green tea's ability to fight cancer. What does the research actually show?
A major review will be conducted in 2021 found a little bit evidence for the role of green tea in cancer prevention. However, laboratory studies show that EGCG blocks the paths is involved in tumor formation, says Dr. James Segars, a cancer researcher and chief of reproductive endocrinology at Johns Hopkins University.
Other studies show a link between green tea and a reduced risk of certain cancers, such as breast, ovarian, prostateAnd neck“It can be protective,” Acosta says, as part of an overall healthy lifestyle. Segars research cells to see how green tea can reduce the size of fibroids, abnormal masses of tissue that can develop into uterine cancer. He advises patients with a family history of fibroids to take two 400-mg tablets of green tea extract daily.
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Theoretically, green tea may even help with treatment cancer, partly because high doses appear to contribute to death cancer cells. More research is needed on these effects, Segars says. Dr. Mary E. Money, an internist, was diagnosed with advanced ovarian cancer in 2012. A few years later, she was impressed by the research on green tea and cancer and began drinking six to eight cups of the beverage throughout the day instead of taking the extract pills — without changing the rest of her regimen. Her Cancer biomarkers have improved significantlyshe says. Money continues to receive chemotherapy when needed; green tea may work synergistically With chemotherapy In some cases, research shows,
However, the evidence is mixed: Other studies suggest that antioxidants, including those found in tea, may interfere with some cancer treatments, such as chemotherapy and radiation therapy.
Mani notes that her experience is just one anecdote. She may be a super-responder, while others’ reactions depend on a variety of factors, including their specific diagnosis, treatment strategy, and overall diet. “There are so many variables,” she says. One thing is clear: Overall, green tea is a healthy choice.