News Today: No, You Can't Drink Unlimited Amounts of Green Tea Without Consequences

Green tea is linked to many health benefits, but it can also cause unwanted side effects.

Green tea is a popular beverage consumed worldwide. 

In recent years, it has also gained popularity as a health drink.

Green tea is derived from the leaves of the Camellia sinensis plant and comes in several varieties.

It can be enjoyed hot, cold or even in powdered form, and it’s recognized for its high antioxidant content and health benefits.

But how much green tea should you drink to achieve these benefits? And could drinking too much be dangerous?

This article dives into the research to find out how much green tea you should drink.

Green Tea Is Linked to Many Health Benefits

Green tea is loaded with nutrients and plant compounds that can have positive health effects.

This includes potent antioxidants called catechins, which may help protect against cancer. 

In fact, multiple studies show that people who drink green tea are significantly less likely to get many types of cancer, compared to those who don’t drink it (1, 2).

The cancers that green tea may help protect against include prostate and breast cancer, which are the two most common cancers in men and women, respectively (3, 4).

What's more, several studies indicate that green tea may lower your risk of developing type 2 diabetes and heart disease (5, 6, 7, 8).

And drinking green tea may even help you lose weight.

The caffeine and catechins it contains have been shown to boost your metabolism and increase fat burning (9, 10).

Overall, studies indicate that consuming green tea can help you burn an additional 75–100 calories per day (11).

Although this may seem like a small amount, it can contribute to significant weight loss over the long term.

Other possible benefits of drinking green tea include immune system support, improved brain function, improved dental health and a lower risk of arthritis, Alzheimer's and Parkinson's disease (12, 13, 14).

SUMMARY: The compounds in green tea can have powerful effects on health, including a decreased risk of cancer, diabetes and heart disease. 

How Much Green Tea Is Optimal?

Studies that explore the benefits of green tea show conflicting evidence about exactly how much you should drink each day.

Some studies show health benefits in people who drink as little as one cup per day, while other studies deem five or more cups per day to be optimal (15, 16).

Green tea may help lower the risk of several diseases. However, the optimal amount to drink may depend on the disease.

• Oral cancer: In a large observational study, women who drank three to four cups of green tea daily were the least likely to develop oral cancer (17).
• Prostate cancer: A large observational study found that men who drank five or more cups of green tea daily had a lower risk of developing prostate cancer, compared to those who drank less than one cup per day (18). 
• Stomach cancer: Another large observational study showed a reduced risk of stomach cancer in women who consumed five or more cups of green tea per day (19). 
• Breast cancer: Two observational studies showed reduced recurrences of breast cancer in women who drank more than three cups of green tea daily (20, 21).
• Pancreatic cancer: One observational study found that drinking five or more cups of green tea per day was linked to a decreased risk of pancreatic cancer (22).
• Diabetes: In a retrospective observational study, people who consumed six or more cups of green tea daily had a 33% lower risk of developing type 2 diabetes, compared to those who consumed less than one cup per week (23).
• Heart disease: An analysis of nine studies found that people who consumed one to three cups of green tea daily had a lower risk of heart attack and stroke, compared to those who drank less than one cup (24).

Based on the above studies, it’s optimal to drink three to five cups of green tea per day.

However, it's important to note that some studies did not find any association between drinking green tea and disease risk, so these effects may vary from person to person (25, 26).

One thing most studies have found is that green tea drinkers are in better health than those who do not drink tea at all.

SUMMARY:T he amount of tea required for health benefits varies greatly among studies. Drinking a minimum of three to five cups of green tea per day seems to work well, but the optimal amount may vary from one person to the next. 

Possible Side Effects of Drinking Green Tea

The caffeine and catechins in green tea are well known for their health benefits, but they can also cause side effects for some people, especially in large doses.

Effects of Caffeine

Consuming too much caffeine can increase feelings of anxiety, interfere with sleep and cause stomach upset and headaches in some people (27, 28, 29, 30, 31).

Consuming large amounts of caffeine while pregnant may even increase the risk of birth defects and miscarriage (32).

Based on current research, everyone, including pregnant women, should not consume more than 300 mg of caffeine daily (33).

However, one review looked at over 400 studies and found that healthy adults who consumed up to 400 mg of caffeine per day did not experience adverse effects (34).

The amount of caffeine in one cup of green tea varies depending on the amount of tea used and the length of time the leaves steep.

One study found that the caffeine content of 1 gram of green tea ranged from 11–20 mg (12).

A single serving is usually measured at 1 tablespoon (2 grams) of tea leaves per 1 cup (240 ml) of water. Assuming each cup of tea is approximately 1 cup (240 ml), this means the average cup of green tea contains about 22–40 mg of caffeine.

Catechins May Reduce Iron Absorption

The catechins in green tea may reduce your ability to absorb iron from foods (35).

In fact, consuming catechins in large quantities may lead to iron deficiency anemia (36).

While regularly drinking green tea isn't a concern for most healthy individuals, those at risk of iron deficiency should consider drinking tea in between meals and waiting at least one hour after eating before drinking tea (37).

Infants, young children, women who are pregnant or menstruating and individuals who have internal bleeding or are undergoing dialysis are all at an increased risk of iron deficiency.

The catechins in green tea can also interfere with certain medications and decrease their effectiveness.

For example, studies indicate that green tea may inhibit the effectiveness of certain heart and blood pressure medications (12).

Drinking green tea may also decrease the effects of certain medications used to treat anxiety and depression (38, 39).

Toxic effects are most common when people take green tea supplements, which have a much higher concentration of catechins than green tea itself (40).

SUMMARY: When consumed in moderation, green tea is safe for most people. You may want to limit or avoid it if you have iron deficiency or are pregnant, nursing or taking medications for anxiety disorders or heart conditions. 

The Bottom Line

Green tea is packed full of health-promoting compounds.

Regularly drinking green tea can help you lose weight and reduce your risk of several diseases, including diabetes, heart disease and cancer.

Drinking three to five cups of green tea per day seems to be optimal to reap the most health benefits.

Very high doses may be problematic for some, but generally, green tea's benefits far outweigh its risks.

In fact, drinking more green tea may greatly improve your health.

 

 

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News Today: No, You Can't Drink Unlimited Amounts of Green Tea Without Consequences