Green Tea: Benefits, Nutrition, and Risks

For thousands of years, people in China and Japan have consumed green tea for its soothing flavor and therapeutic benefits. Research has found drinking green tea may protect against heart disease, help manage type 2 diabetes, and even support bone health.

While green tea is made from the same leaves as black tea, green tea leaves are not fermented. This not only preserves the tea’s green color but also enhances its antioxidant content, which may explain why it’s so healthful.

Here’s an overview of green tea’s health benefits and risks as well as tips for incorporating it into your diet.

Sipping green tea on the regular may help prevent some chronic health conditions and manage others. So far, research has found green tea:

May improve mental health

There is a chemical explanation for why sipping a hot cup of green tea can be so relaxing. Tea—along with some mushrooms—contains an amino acid called theanine, which research has found may:

• Relieve stress
• Induce relaxation
• Combat anxiety from caffeine

Green tea in particular has the highest concentration of theanine compared to other types of tea like oolong, black, and white tea, according to a 2016 study published in Pharmacognosy Magazine.

A 2020 review published in Plant Foods for Human Nutrition found that taking a 200 to 400 milligrams (mg) supplement of theanine daily reduced stress and anxiety in people exposed to stressful conditions.

Another 2019 study, published in Nutrients, of 30 people with no major psychiatric conditions found that those who took 200 mg a day of theanine for four weeks saw greater improvements in depression, anxiety, and sleep compared to those who took a placebo.

While both these studies highlight the potential mental health benefits of theanine, the amounts of theanine they used is much more than the amount you would find in a cup or two of green tea.

Might enhance memory

Research has also found that green tea can improve memory, partially thanks to its theanine content. For example, a 2014 study published in Psychopharmacology of 12 healthy volunteers found that green tea extract improved subjects working memory—a type of short-term memory important for planning, comprehension, reasoning, and problem-solving.

Patients were given a milk-based drink that contained either 27.5 mg green tea extract or a placebo. They then completed certain tasks while an MRI tracked their brain activity. Those who consumed the green tea extract saw greater brain connectivity—aka how well different areas of the brain work together—as well as improved working memory and task performance.

Since the study used such a small sample of patients, the results are less definitive. More research is needed to further explore how green tea influences memory.

Protection against neurodegenerative diseases

Some research has found drinking green tea can protect against certain neurodegenerative diseases, like Alzheimer’s and Parkinson’s. This is likely due to green tea’s high concentration of powerful compounds called antioxidants, according to a 2019 research review published in Molecules. Antioxidants defend cells against damage that, over time, would otherwise lead to neurodegenerative diseases.

A 2022 study published in Frontiers in Nutrition found that after following 1,545 elderly people in China with healthy brain functioning for one year, those who habitually drank tea—including green tea—had lower rates of cognitive decline compared to non-tea drinkers. This was true even after researchers adjusted for factors like education, smoking, and exercise.

Cognitive decline is one of the first noticeable symptoms of Alzheimer’s and related forms of dementia, according to the Centers for Disease Control and Prevention (CDC). It refers to worsening or more frequent instances of confusion and/or memory loss.

Could lower cholesterol

About 38% of American adults have high cholesterol levels, which raises their risk of heart attack and stroke, according to the CDC. The good news? Green tea might help.

A 2020 meta-analysis of 31 studies published in Nutrition Journal found that consuming green tea was associated with lower levels of both total cholesterol and LDL (aka bad) cholesterol.

Can reduce blood pressure

In addition to lowering cholesterol levels, green tea may protect heart health by lowering blood pressure. A 2020 meta-analysis in Medicine of 1,697 people found that drinking green tea significantly reduced blood pressure, particularly in those with high blood pressure and the greatest risk of cardiovascular disease.

That’s key since nearly 50% of heart disease cases and 60% of strokes are due to high blood pressure, per the National Library of Medicine. If high blood pressure is left untreated, it can also lead to kidney failure.

Green tea’s ability to lower blood pressure may be due to its high antioxidant content, according to the same 2020 analysis listed above. These antioxidants reduce inflammation and dilate blood vessels so blood can flow more easily.

However, most of the studies assessed in the analysis only lasted between three and sixteen weeks, meaning it’s not clear how drinking green tea for longer may or may not improve blood pressure.

May prevent stroke

Stroke remains a leading cause of death and disability for adults in the United States, according to the CDC. Drinking green tea may be one way to help prevent your risk of stroke.

For instance, a 2020 study in the American Journal of Clinical Nutrition, tracked the tea-drinking habits of nearly half a million Chinese adults. It found that consuming tea—especially green tea—was associated with a lower risk of stroke. In fact, the more green tea people drank, the lower their risk of stroke.

Potentially protects bone health

Green tea may also prevent the loss of bone mass. For example, a 2022 study published in Nutrients found that of almost 6,500 postmenopausal Korean women, those who did not consume any green tea or consumed less than one cup daily for the past year were more likely to have lost bone mass in their spine or thigh compared to those who drank green tea three times a day.

Reduced bone mass increases the risk of osteoporosis, a disease that makes bones more fragile and can lead to fractures of the hip, spine, or wrist, per the National Library of Medicine. Postmenopausal women in particular are at a greater risk of developing osteoporosis.

This may explain why a 2017 analysis published in Medicine concluded that tea consumption was linked to a reduced risk of osteoporosis, likely due to its high concentration of antioxidants which help prevent bone loss and enhance bone formation.

Helps prevent and manage type 2 diabetes

Consuming tea—including green tea—may be an effective way to prevent and manage type 2 diabetes, according to a 2019 review published in Antioxidants. The review found that green tea antioxidants, in particular, could reduce insulin resistance.

Insulin resistance occurs when cells are less sensitive to the hormone insulin, which helps cells convert blood sugar to energy. It is one of the major risk factors for developing type 2 diabetes, according to the CDC.

Improved longevity

Drinking tea, including green tea, is associated with a longer and healthier life, according to 2020 research published in the European Journal of Preventive Cardiology.

The study followed 100,902 participants in China with no history of heart attack, stroke, or cancer for over seven years. It grouped participants as either:

• Habitual tea drinkers, meaning they consumed tea three or more times a week.
• Non-habitual tea drinkers, meaning they consumed tea less than three times a week. .

Compared to non-habitual tea drinkers, those who drank tea three or more times a week had a reduced risk of mortality from all causes. They also had a reduced risk of developing atherosclerotic cardiovascular disease, which is when plaque builds up in blood vessels, increasing the risk of heart attack or stroke, according to the American Heart Association (AHA).

Green tea, in particular, was associated with a lower risk of dying from all causes except for coronary heart disease. Researchers believe this is likely due to antioxidants in green tea protecting cells from damage that would otherwise lead to disease.

Green tea is not a significant source of calories, vitamins, or minerals per cup. According to the USDA, eight brewed ounces contains:

• Calories: 2.45
• Fat: 0g
• Sodium: 2.45mg
• Carbohydrates: 0g
• Protein: 0.5g

Tea also contains various antioxidants and small amounts of 27 minerals, according to a 2022 review published in Chinese Medicine These include:

• Potassium, which helps keep you hydrated.
• Magnesium, which helps control blood sugar.
• Selenium, which supports our immune system.

While the amounts are quite small, they can add up, depending on your total daily green tea intake.

It is safe to consume up to eight cups of green tea per day, per the National Center for Complementary and Integrative Health (NCCIH), a division of the National Institutes of Health (NIH). But the organization cautions that high doses may interact with certain medications, like those for high blood pressure or heart problems. While uncommon, liver problems have also been linked to the use of tea products, primarily green tea extracts taken in pill form.

Whether you sip your green tea hot or chilled, there are a few tips to keep in mind:

• Consider buying naturally decaffeinated green tea. One cup of green tea contains 28 grams of caffeine, per Mayo Clinic. For those sensitive to caffeine, this may cause anxiety, fast heart rate, and jitters. Note that removing the caffeine may lower the antioxidant content, but research is mixed.
• Be mindful of your sweetener. If you add sugar, honey, or another sweetener to your tea, remember the AHA advises women consume no more than six teaspoons of added sugar a day, and men no more than nine teaspoons. Excess sugar consumption can contribute to weight gain, type 2 diabetes, and heart disease.
• Get creative. While green tea can be enjoyed on its own, you can also use it in smoothies and oatmeal or for boiling rice and steaming vegetables.

Green tea is a staple in many cultures and may offer some important health benefits, like protecting our brain, heart, and bone health. Even so, it can carry some health risks for those on certain medications or with a caffeine sensitivity. If you don’t currently drink green tea and you’re not sure if it’s right for you, ask your healthcare provider or dietitian for guidance about how it may impact your personal health goals.

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