Just how healthy is green tea, anyway?

Created date

December 30th, 2019
Scientific evidence suggests that green tea may have positive effects on heart disease, brain health, as well as the common cold.

Scientific evidence suggests that green tea may have positive effects on heart disease, brain health, as well as the common cold.

Whether it is black, green, oolong, or white, all tea comes from the same plant (camellia sinensis). The different types result from how and where the tea is grown and how it is manufactured.

Green is good 

“All types of tea may be beneficial in different ways,” says Jerlyn Jones M.S., M.P.A., R.D.N., L.D., C.L.T., spokesperson for the Academy of Nutrition and Dietetics. “Research shows, however, that green tea may be more beneficial than other varieties.”

Scientists think that the health benefits are related to a class of compounds called polyphenols. “These compounds have antioxidant properties and help rid the body of free radicals, which are molecular compounds associated with the development of many diseases,” Jones explains.

All tea contains polyphenols, but green tea has the most—especially a certain type called catechins. That’s because green tea is minimally processed, so high amounts remain in the leaves.

Research results of interest

The National Center for Complementary and Integrative Health (NCCIH) analyzes the available scientific evidence on products (such as herbs, tea, and other so-called natural remedies) and practices (such as mind-body exercises, meditation, and acupuncture) that people use along with, or instead of, traditional medical practices. NCCIH’s latest stance after evaluating green tea studies is that “definite conclusions cannot yet be reached on whether green tea is helpful for most of the purposes for which it is used.”

Research, however, is producing promising results. According to NCCIH, some limited scientific evidence suggests that green tea may have positive effects on heart disease risk factors, such as blood pressure and cholesterol levels.

“A large study conducted in Japan showed a link between green tea consumption and a lower death rate from cardiovascular conditions,” Jones says. “The study subjects, however, were drinking up to seven cups [8 oz] of tea daily.”

Other encouraging research concerns brain health. “Some study results indicate that green tea may have a protective effect against neurodegenerative diseases and cognitive impairment,” Jones says. “This includes dementia-related illnesses.”

Green tea may also be able to prevent certain infections. Authors of a large review study conducted in 2018 concluded that there is evidence that green tea may have preventive effects on influenza and the common cold. 

One of the studies the authors reviewed was conducted in a nursing home. Residents were given either green tea or water to gargle with. After three months, the green tea group had a significantly lower incidence of the flu compared to the plain water group. 

Research pertaining to green tea and its possible effect on cancer has been of great interest to scientists and consumers alike. Study results, however, have been too inconsistent to arrive at any definite conclusions on whether green tea can reduce the risk of any type of cancer. In addition, the National Cancer Institute does not recommend for or against using any form of green tea to reduce your risk of cancer.

Safety of green tea

According to the U.S. Food and Drug Administration (FDA), green tea as a beverage is believed to be safe in moderate amounts.

“Although green tea is naturally low in caffeine, it still contains some—anywhere from about 14 mg to 70 mg per 8-oz serving of hot brewed tea,” Jones says. “Some people may be sensitive to even small amounts of caffeine.”

Several safety studies have examined green tea extracts. Some of the adverse effects reported with higher doses included excess intestinal gas, nausea, heartburn, abdominal pain, dizziness, headache, and muscle pain. “There have also been reports of liver toxicity in people who take green tea extracts,” Jones adds. 

Green tea in extract (supplement) form is considered to be a dietary supplement. Although the FDA has some oversight of dietary supplements, they do not undergo the rigorous testing for safety and efficacy that medicines do. They can contain unlisted ingredients, and one analysis of the catechins and caffeine content in 19 different green tea supplements found that the actual amounts were different from what was listed on the labels.  

In addition, green tea extracts can interact with other medications. “Always check with your health care provider before starting green tea extracts or any dietary supplement for that matter,” Jones says. 

The best way to consume green tea? Drink it!

“To reap the benefits of green tea, brew it at home and keep it as plain as possible,” Jones advises. “Anything you add might dilute the concentrations of healthy compounds, and people tend to add sugar, honey, cream, or other products that can rack up unnecessary calories.”

Be careful of what you get at the coffee shop or on store shelves. “Just because something contains green tea doesn’t mean it is a healthy choice,” Jones says. “Some of the combination drinks at the coffee shop may actually contain very little brewed green tea, and bottles on store shelves usually have a lot of sugar or other sweeteners.”

Just keep in mind, scientists still don’t know for sure how healthy green tea is. “Much more research needs to be conducted,” Jones says. “As with all food and drink, moderation is a good rule to follow.”