All About Green Tea: Why It’s Good for You and the Risk of Drinking Too Much

Water is obviously the most-consumed beverage in the world, but what’s in the No. 2 spot? According to Consumer Reports, that’d be tea. (1) More than 159 million Americans enjoy it every day. (2)

One of the most popular types is green tea — and it’s not just because people like the taste. Green tea is prized for being one of the healthiest beverages available, so much so that it’s achieved superdrink status in recent years. (3)

All tea comes from the same plant, Camellia sinensis, but the leaves are processed differently to make green, black, and oolong tea, according to the National Center for Complementary and Integrative Health (NCCIH). Green tea leaves are not allowed to oxidize, which accounts for their fresh, almost grassy flavor.

Tea drinking is a ritual that people have been practicing for centuries, dating back to 2700 B.C. in Asia, according to some accounts. It’s known for its high content of antioxidants called catechins (more on those later) and is also beloved for its crash- and jitter-free dose of caffeine, thanks to its generous supply of L-theanine, an amino acid that research has found to have a calming effect on the nervous system. Melissa Salazar, an International Tea Master Association–certified tea master, says that green tea has the highest quantity of L-theanine compared with other teas. “It helps to increase brain waves, which induces deep relaxation and increases focus,” she adds. “This makes green tea a very special plant indeed.”

Some small studies have observed this, finding the L-theanine to increase alpha wave emission in people with anxiety, as well as improve mental alertness. A study of 69 Japanese men and women found that it improved attention and memory-related tasks.

With that said, some green tea blends have more caffeine than others, and matcha, a popular powdered form of green tea, has the most. That’s because it’s made by grinding the entire Camellia sinensis leaf, explains Salazar, and is delivered to the body in its entirety, as opposed to tea leaves that are steeped in water and then removed prior to serving. Matcha’s unique preparation also makes it more plentiful in the good stuff, like antioxidants.

Today, green tea is still most commonly sipped in drink form, but it’s also finding its way into supplements, skin care, and more.

Brewed green tea is primarily water, which means it’s free of the usual macronutrients found in other foods and drinks. It doesn’t contain any fat, carbohydrates, or protein, and there aren’t any calories in unsweetened tea. It gets its healthy reputation from compounds called catechins, specifically epicatechin, epicatechin-3-gallate, epigallocatechin, and EGCG. These catechins have anti-inflammatory, antimicrobial, and even anti-cancer effects, according to a review. They’re also believed to have probiotic benefits, per a study.

A cup of green tea has around 28 milligrams (mg) of caffeine, which puts it slightly behind black tea’s 47 mg, according to the Mayo Clinic.  There can be a lot of variation in caffeine content, depending on how the tea was processed and brewed, however.

The amount of catechins per cup also varies, with a systematic review defining a range between 25 mg and 750 mg per cup.

Green tea's benefits may include:

• Increased Mental Alertness A review found that caffeine, particularly the amount in matcha, improved alertness, arousal, and vigor during long, demanding cognitive tasks.
• Protection Against Heart Disease Not many long-term studies have been done, but the ones that have been completed suggest that green tea’s antioxidants may help lower high blood pressure (hypertension) and keep cholesterol in check, reducing the risk of developing heart disease. A Japanese study found that people who consumed 5 or more cups of green tea each day had a 26 percent lower risk of dying of cardiovascular disease during a seven-year period compared with people who drank only 1 cup per day. More recently, a study surveyed health data of 100,000 participants and found that those who frequently drank tea were 20 percent less likely to suffer from heart disease or stroke — and green tea had the strongest impact.
• Lower Cholesterol A systematic review and meta-analysis concluded that green tea consumption lowers levels of LDL ("bad") cholesterol in people of all body weights.
• Cancer Prevention Some researchers suspect that catechins have the ability to block cancer-causing free radicals. Research has been inconsistent, though, and according to the National Cancer Institute, drinking green tea isn’t a proven way to protect against cancer.
• Reduced Risk of Diabetes In a study of a half million Chinese adults, daily green tea consumption was associated with a lower risk of type 2 diabetes and a lower risk of all causes of mortality in patients with diabetes.

You’ve probably heard that sipping green tea can turn your body into a fat-burning machine. The thinking is that the caffeine and catechins found in the tea work together to send the metabolism into overdrive, which helps the body burn calories and, as a result, drop pounds.

It sounds too good to be true — and it is. These claims come from studies that presented green tea as the secret to weight loss, but most of them were small and short term, and often involved green tea extracts rather than cups of brewed tea. Unfortunately, expecting green tea to produce a significant change in your waistline isn’t realistic.

“Evidence from clinical trials are mixed in their findings of weight loss associated with green tea consumption,” says Caroline West Passerrello, RDN, a spokesperson for the Academy of Nutrition and Dietetics. “Extracts that are rich in ECGC may increase calorie and fat metabolism — maybe because of the catechins, caffeine, and theanine — and it might suppress appetite in animal research. Impact remains undetermined with well-designed studies.”

A study analyzed the effects of green tea extract on overweight women with high LDL cholesterol levels compared with a placebo. After six weeks, there were no significant changes in participants’ weight. Additionally, a review of 15 clinical trials found that green tea was only effective for weight loss when combined with 80 to 300 mg of caffeine per day.

On its own, however, plain, unsweetened green tea is a low-calorie beverage that is part of a sensible diet and will save you calories when swapped for sugary soda, juice, or high-calorie coffee drinks.

The type of green tea you choose will depend on the benefits you’re seeking, explains Salazar. If you’re looking for the maximum amount of caffeine and antioxidants, she says that matcha is your best bet. You can also steep the leaves of your favorite Chinese variety, she adds. It’s all a matter of trial and error to find what you like.

Preparations vary slightly depending on the tea type, as well as taste preference. But it’s important to know that green tea, overall, is sensitive to high temperatures and can get bitter if boiled, per Salazar. “The general rule of thumb is that you use a lower temperature than boiling,” she explains, which is anywhere from 150 to 175 degrees F.

“I like to brew my matcha at 165 degrees,” she adds. “How delicate the leaves are will determine the actual steeping time.” She recommends measuring out 1 teaspoon of leaves per 6 ounces of water and steeping for one to two minutes. And if you want to enjoy your cup cold, no need to worry about sacrificing its benefits — Salazar says that they don’t really differ from hot to iced. “For iced tea, you would simply steep the tea as you would and then pour over ice,” she adds.

Although green tea is generally considered safe and healthy, thanks to its many proven benefits, as with any food or drink, there can be too much of a good thing. Because green tea contains caffeine, drinking too much of it can lead to classic signs of caffeine overconsumption, such as feeling jittery and having trouble with sleep, per the NCCIH.

Consuming green tea in the form of concentrated extracts can also end up damaging the liver. A study found that women who took a high dose of green tea extract (equivalent to 5 cups of brewed tea) daily developed high levels of liver enzymes, which could indicate that the cells within the liver have been damaged.

The take-home message here? Approach green tea extracts with caution because they’re not regulated by the U.S. Food and Drug Administration (FDA). But if you decide you want to try them, experts recommend taking them only at mealtime and to stop taking them and see a doctor if you notice signs that your liver’s in trouble, such as if you have especially dark urine or experience abdominal pain.

Also, stay away from green tea if you have a heart condition or other cardiovascular problems, or renal failure, and limit your intake to no more than 2 cups per day if you’re pregnant or breastfeeding, according to research. It’s a good idea to consult your healthcare provider for individual recommendations.

Even if you’re not a fan of the taste of green tea, a quick trip to any grocery store, not just health food stores, will turn up green tea in dozens of products:

• Classic brewed tea
• Powder
• Bottled beverages
• Supplements
• Weight loss products

Experts caution not to overdo the supplements and weight loss products because the FDA doesn’t regulate them. Everything else, though, is relatively safe.

If weight loss is your goal, be sure to check the ingredient label of green tea beverages. Regular, unsweetened tea is always a better bet than the sweetened bottled versions, which may have loads of added sugars. Unsweetened Green Tea from Pure Leaf, for instance, has 0 calories and 0 grams of (g) sugar in 18.5 ounces, while Arizona Green Tea packs 130 calories and 34 g of sugar into 8 ounces. Keep in mind, too, that sweetened, packaged teas often come in larger portions than the regular, unsweetened variety, which means they have a greater potential to lead to weight gain.

You may spot green tea as an active ingredient in skin-care products because its anti-inflammatory properties and antioxidants make it an effective multitasker, according to Marisa Garshick, MD, a dermatologist at Medical Dermatology and Cosmetic Surgery in Commack, New York, and an adviser to BioRepublic. Some research has found that the EGCG in green tea has antimicrobial activity, which may help inhibit the growth of bacteria that cause some difficult to treat skin infections.

The polyphenols in green tea may also prevent sun damage with their anti-inflammatory and antibacterial properties, a study found. Catechins have been found to have a moisturizing effect on skin, which may help reduce the appearance of fine lines, age spots, and wrinkles. “It’s also a powerful antibacterial agent for treating acne and unclogging pores,” Dr. Garshick adds, although only small, limited studies have been done on this topic, and further research is necessary. “Green tea is chock-full of vitamin B2 and vitamin E, both essential for skin health,” she says.

Green tea is a plant-based beverage that has been used medicinally for centuries, and plenty of research backs up its health-boosting properties. It’s high concentration of antioxidants and versatility make it a popular drink, as well as an ingredient to add to other foods and wellness products. Because it contains caffeine, however, it is important to use caution with supplements and extracts, and only use them in the recommended amounts.

Additional reporting by Kayla Blanton.