Green tea is an unfermented tea that's very rich in antioxidants. The benefits of drinking green tea primarily come from these beneficial bioactive compounds. Green tea can protect your cardiovascular system and liver and help prevent certain types of cancer.
Green tea is a healthy beverage, but you shouldn't ingest excessive amounts of it. If you're drinking highly caffeinated green tea, you should limit your green tea intake to about 9 cups a day. However, if you're drinking cold-brewed green tea, which has less caffeine, you can safely consume as much as 16 cups per day.
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Green Tea and Your Health
Teas are typically considered good for you because they're rich in beneficial bioactive compounds. Drinking green tea is a particularly healthy choice. According to an August 2013 study in the Journal of Functional Foods, unfermented green tea has more antioxidants compared to fermented teas, like oolong tea and black tea.
Green tea is particularly rich in antioxidants known as flavonoids. Catechins, a type of flavonoid, are considered the most beneficial type of antioxidant green tea contains. Although green tea has a variety of beneficial bioactive compounds, most of its health benefits are attributed to its substantial catechin content.
The average cup (8 ounces or 237 milliliters) of green tea has 5 percent of the daily value (DV) for phosphorus. It also has small amounts of copper and potassium (1 percent of the DV per cup).
Green tea is also rich in vitamin C. The USDA listing for matcha green tea states that it has 13 percent of the DV for this nutrient in every cup.
Essentially, this means your powdered green tea may have different nutritional benefits compared to your average tea bag, like Lipton's. Similarly, Lipton green tea's benefits may be different from those of the loose leaf tea you brew at home.
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Benefits of Drinking Green Tea
Green tea is thought to have a variety of health benefits. According to a January 2012 study in the Global Journal of Pharmacology and a June 2012 study in the Journal of the Indian Society of Periodontology, green tea can help:
- Support weight loss.
- Support immune system function and reduce inflammation.
- Support healthy bones.
- Lower cholesterol levels.
- Reduce the risk of cardiovascular diseases like stroke.
- Protect the liver and prevent liver disease.
- Help prevent certain types of cancer, particularly stomach cancer and colorectal cancer.
- Improve oral health.
- Prevent dental plaque from forming.
- Protect your skin's health.
- Counteract bacterial and viral infections.
Many of the benefits of drinking green tea are attributed to the consumption of a moderate amount of green tea per day. Around 3 to 4 cups per day is usually the average recommended amount. However, some benefits have been attributed to much larger amounts (such as 10 cups per day).
Green tea's cardiovascular benefits have been particularly well studied. According to a January 2016 review in the International Journal of Cardiology, people who didn't consume green tea were at a higher risk for cardiovascular disease and stroke compared to regular green tea drinkers. Specifically, people who consumed 1 cup or more of green tea each day were at a reduced risk for heart attacks and stroke compared to people who didn't drink green tea or consumed it irregularly.
However, the benefits of drinking green tea were enhanced in people who consumed even more green tea each day. People who drank 10 cups or more had reduced cholesterol levels compared to moderate green tea drinkers who consumed 3 cups or less per day.
A June 2013 study in the World Journal of Gastroenterology reported that the best benefits of drinking green tea were seen when people consumed 7 to 10 cups of green tea per day or more. This amount helped prevent stomach cancer, gastritis and other issues.
The same study reported that drinking between 8 and 16 cups of green tea per day is safe. However, if you plan to consume such a large amount of green tea, you should be careful of your caffeine intake.
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Caffeine in Green Tea
Green tea is a particularly good drink for people who prefer beverages lower in caffeine. The Mayo Clinic states that the average 8-ounce cup (237 milliliters) of freshly brewed coffee has 95 to 165 milligrams of caffeine. In contrast, green tea typically has 25 to 29 grams of caffeine per cup.
However, according to a January 2014 article published in the journal Separation & Purification Reviews, green tea's caffeine content can range between 10 to 45 milligrams per cup. This amount of variation can occur because of simple brewing differences, like variations in the amount of tea leaves or water you use, or how long you let your tea brew. The species, freshness and age the tea leaves were harvested at can also influence your tea's caffeine content.
Although green tea has many benefits, you shouldn't drink too much of it. The Mayo Clinic recommends limiting your caffeine consumption to a total of 400 milligrams per day. Teens should limit caffeine to no more than 100 milligrams per day, according to University of Michigan Medicine.
Too much caffeine can irritate your gastrointestinal tract, affect your energy levels and cause issues like insomnia. In excessive amounts, caffeine can even be toxic and cause vomiting, arrhythmia and convulsions.
Healthy Tea Consumption and Caffeine
To stay within the Mayo Clinic's recommended caffeine intake, most people should limit their green tea consumption to no more than 14 or 15 cups per day. However, this quantity assumes that your tea has a fairly average caffeine content. If you prefer stronger teas (like those brewed with young, fresh leaves), you may want to limit your green tea consumption to a maximum of 9 cups per day.
If you're keen to obtain the benefits of drinking green tea but don't want to ingest that much caffeine, try drinking decaffeinated green tea instead. According to the Separation & Purification Reviews study, decaffeinated green tea has no more than 4 milligrams of caffeine per gram of tea leaves. There's also a maximum of 10 milligrams of caffeine per gram of ground tea powder.
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If you're not a fan of decaf but still want to reduce the caffeine content in your green tea, you can also try drinking cold-brewed tea. A July 2015 study in the Journal of Food Science and Technology reported that steeping your tea in cold water reduces its caffeine content while increasing the amounts of beneficial bioactive compounds.
To maximize the benefits of green tea, cold brewing may actually be the best way to go. The same study reported that antioxidants in tea can be destroyed by hot temperatures of over 194 degrees Fahrenheit (90 degrees Celsius). Although many people like to steep their tea in hot water, this means that boiling water's temperature (212 degrees Fahrenheit or 100 degrees Celsius) is actually damaging the beneficial compounds in your green tea.
Disadvantages of Green Tea Consumption
There aren't many disadvantages to green tea consumption. The main limitation is usually green tea's caffeine content, which limits how much certain people can drink. Fortunately, brewed green tea rarely produces caffeine-related issues. You're more likely to have an issue with excessive amounts of caffeine if you're taking green tea supplements.
However, drinking excessive amounts of green tea can cause other types of issues. The June 2012 study in the Journal of the Indian Society of Periodontology reported that excessive green tea consumption can prevent your body from absorbing certain essential nutrients, like iron and thiamine (vitamin B1).
The same study reported that green tea has the potential to interact with specific types of medications. If you drink large amounts, the disadvantages of green tea include reducing the effectiveness of certain antibiotics. It also has the potential to negatively interact with medications that are used to treat mental health issues. Excessive green tea consumption may even increase your risk of bladder cancer.
Keep in mind that all of these potential side effects are associated with drinking too much green tea. There are very few disadvantages to green tea consumption in moderation. The main issue green tea drinkers may want to take into account is related to contaminants.
Heavy Metal Contaminants in Tea
According to a September 2013 study in the Journal of Toxicology, teas are often contaminated with heavy metals. This study found contaminants in various types of tea produced across multiple countries. The green tea products they tested were found to contain high levels of aluminum as well as medium-to-high levels of lead.
In small amounts, heavy metals are not a major health concern. However, heavy metals can be a serious issue for certain people, like pregnant women and nursing mothers. They can also become problematic for any person ingesting large amounts.
If you're drinking a lot of tea each day, it's possible that you might be ingesting excessive amounts of heavy metals too. The authors of this study recommended that people concerned about heavy metal intake limit their consumption of tea to 4 cups per day. Pregnant women and lactating mothers may want to avoid consuming tea or severely restrict their tea consumption.
That being said, this study reported that most of these heavy metal contaminants were released when tea leaves were steeped for long periods of time (15 minutes). If you're keen on drinking large amounts of green tea each day, it may be best to steep your tea for short periods of time (3 minutes or less).
Unfortunately, this also means that avid tea drinkers may want to avoid the cold-brewed tea recommended in the study in the Journal of Food Science and Technology. Cold-brewing typically involves steeping your tea for several hours.
- American Journal of Geriatric Psychiatry: "Green Tea Consumption and the Risk of Incident Dementia in Elderly Japanese: The Ohsaki Cohort 2006 Study"
- Public Health Nutrition: "Green Tea and Coffee Consumption Is Inversely Associated With Depressive Symptoms in a Japanese Working Population"
- Mayo Clinic: "Caffeine Content for Coffee, Tea, Soda and More"
- Separation & Purification Reviews: "Caffeine in Green Tea: Its Removal and Isolation"
- Journal of Food Science and Technology: "Effects of Alternative Steeping Methods on Composition, Antioxidant Property and Colour of Green, Black and Oolong Tea Infusions"
- Journal of Toxicology: "The Benefits and Risks of Consuming Brewed Tea: Beware of Toxic Element Contamination"
- Journal of Functional Foods: "Green Tea Extract: Chemistry, Antioxidant Properties and Food Applications – A Review"
- USDA: "Nutrition Comparison of Brewed Matcha Tea vs Green Tea"
- Global Journal of Pharmacology: "Camellia sinensis (Green Tea): A Review"
- Journal of the Indian Society of Periodontology: "Green Tea: A Boon for Periodontal and General Health"
- International Journal of Cardiology: "Green Tea Consumption and Risk of Cardiovascular and Ischemic Related Diseases: A Meta-Analysis"
- World Journal of Gastroenterology: "Green Tea and the Risk of Gastric Cancer: Epidemiological Evidence"
- University of Michigan Medicine: "Parents, Perk Up to the Dangers of Caffeine for Teens"