Benefits, Side Effects, and More

Green tea is one of the oldest beverages known to man. Originating in China, this drink comes from the leaves of the Camellia sinensis plant and may date as far back as 3,000 years ago. Today, you can enjoy green tea in everything from smoothies to cheesecakes—but it’s still an excellent solo beverage, too. 

Other than its earthy yet mild taste, green tea offers numerous health benefits, especially because of its abundant levels of antioxidants. Here’s a look at how regularly drinking this mild beverage could improve your health. 

Green Tea Nutrition

Green tea contains two calories per 1-cup serving and no significant amounts of protein, fat, carbohydrates, or sugar—unless you add something to the tea like honey or raw sugar. But this mild beverage is rich in antioxidants, making it a nutritious choice. According to the USDA, 1 cup of brewed green tea contains the following nutrients.

Potential Health Benefits of Green Tea

A mug here or there of green tea probably won’t yield major health benefits—but making a habit of drinking it often might add up to some surprising perks for wellness. (Up to 8 cups per day is considered safe, though you need to consider its caffeine content to determine what is right for you.) The following are some potential health benefits of regularly drinking green tea.

May Improve Cognitive Health and Focus

If you have an important test or presentation coming up, imbibing green tea beforehand could improve your focus. A review that analyzed 49 studies concluded that people who drank green tea showed improved performance on long-duration cognitive tests, as well as better self-reported alertness. The study’s researchers postulated that green tea’s energy-boosting caffeine and calming L-theanine combine to support a state of focus.

Could Support the Immune System

Green tea is a hot beverage that can feel soothing when you’re sick. But it also may be able to prevent illness, says Wan Na Chun, MPH, RD, CPT, a registered dietitian, personal trainer, and owner of One Pot Wellness in Indianapolis.

“Green tea contains powerful antioxidants that can provide immune support through several mechanisms,” says Chun. “Catechins, particularly epigallocatechin gallate (EGCG), are the main antioxidants in green tea that promote immune function. These compounds help strengthen the immune system by protecting it against oxidants and free radicals, reducing overall oxidative stress in the body.” 

Chun says studies have shown that green tea catechins can promote the proliferation of immune-strengthening T-cells and natural killer cells, modulating inflammatory responses. “Additionally, green tea polyphenols may positively influence gut microbiota and boost the body’s production of antioxidant enzymes.”

May Support Heart Health

Green tea also may support cardiovascular health in several ways. For starters, some research has linked drinking green tea with significantly reduced cholesterol levels. Other studies have found that green tea consumption could yield small reductions in blood pressure.

In a meta-analysis, healthy adults who supplemented their diet with green tea experienced average reductions of 2.99 mmHg of systolic blood pressure and 0.95 mmHg of diastolic blood pressure. Because both cholesterol and blood pressure levels are important indicators of heart health, these measures could have a meaningful impact on overall cardiovascular wellness.

Could Play a Role in Preventing Some Cancers

Quite a lot of research has examined whether green tea could play a role in cancer prevention. Smaller studies have linked green tea (and its more potent extract form) with varying degrees of success in staving off cancer of the prostate, breasts, bladder, ovaries, and more. 

Despite these promising results, more research is needed to make any definite conclusions about a green tea-cancer connection. The National Center for Complementary and Integrative Health (NCCIH) doesn’t recommend for or against using green tea to reduce the risk of any cancer.

Could Reduce Symptoms of Inflammatory Bowel Disease

Green tea is rife with antioxidants—the compounds that reduce inflammation by clearing cells of harmful free radicals. It’s not surprising, then, that this beverage might improve symptoms of inflammatory conditions like Crohn’s disease and ulcerative colitis.

According to research, green tea’s polyphenols are implicated in the inflammatory processes and severity of symptoms in people with inflammatory bowel disease. If you live with Crohn’s or ulcerative colitis, drinking green tea as part of an anti-inflammatory diet might be worth a try.

Possible Side Effects

Though side effects are unlikely from drinking moderate quantities of green tea, caffeine is cause for concern if you drink copious amounts, says Chun. “[Green tea’s] caffeine content can lead to insomnia, anxiety, irritability, and digestive issues such as nausea, acid reflux, and diarrhea in caffeine-sensitive individuals.”

Additionally, the tannins in green tea can increase stomach acid, potentially causing stomach irritation and exacerbating conditions like acid reflux or ulcers, she adds. Green tea also can interact with certain medications. Check with a healthcare provider or pharmacist to prevent any adverse medication interactions.