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Green Tea Facts, Health Benefits And Side Effects

facts about green tea

Green tea is a popular drink in many cultures, and for a good reason. It’s packed with antioxidants and other nutrients. The advantages of drinking this tea often outweigh the disadvantages.


With that said, people often consume far more green tea than what is considered healthy, unaware of the likely side effects. What are these side effects? And how much green tea should you drink if you’re trying to maximize its benefits and minimize any possible detriments? Read on to learn about both the disadvantages of green tea and the amounts that are safe for consumption.

Green Tea Health Benefits

The key to the health benefits of green tea is the high concentration of antioxidants called catechins. Catechins are also found in fruits like plums, cherries, oranges, and grapefruits. 

Some of the advantages of drinking a cup or two of green tea daily include:

Reduced Risk Of Cardiovascular Disease

Green tea has been shown to aid in reducing the risk of cardiovascular diseases. It is rich in catechins that protect LDL (bad cholesterol) from oxidation and reduce inflammation in blood vessels (12). 

Improved Dental Health

Tea drinkers don’t suffer from dental caries as much as coffee drinkers because green tea inhibits bacteria responsible for tooth decay; it also kills bacteria and viruses and prevents plaque formation and gingivitis (8).

Reduced Cancer Risk 

Studies suggest that the catechins in green tea may stop tumor cells from growing and prevent cancers of the oral cavity, skin, lung, and breast. Green tea is effective in destroying cancerous cells in the bladder and colon (2).

facts about green tea

Enhanced Immunity

Antioxidants combat free radicals, which cause damage to immune system cells. This helps enhance immunity, enabling your body to fight off infections better (2).

Weight Loss

The combination of caffeine and catechins in green tea speeds up metabolism, leading to a mild form of natural weight loss. Both caffeine and catechins also suppress appetite by increasing the levels of glycogen in the liver, which results in a lesser intake of food (22). 

Boosted Energy Levels 

Catechins in green tea increase the metabolic rates of cells, which results in increased energy levels. Studies have shown that even moderate consumption of green tea can result in 7% more energy expenditure! Green tea also contains caffeine, about a quarter the amount found in coffee beans, half the caffeine found in black teas, and one-eighth the level of caffeine present in coffee.

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Healthy Skin 

Green tea contains polyphenols that are known to reduce damage caused by ultraviolet radiation to skin cells, leave your skin smoother, and add a glow to your face without causing any harm or burning sensation. 

Green tea has been shown to protect against sunburn, reduce wrinkles and slow down the aging process because it is packed with antioxidants (19).

facts about green tea

Protection Against Diabetes 

Green tea containing high levels of catechins protects against diabetes by preventing the formation of advanced glycation end products (AGEs). AGEs lead to high blood sugar levels and affect immune cells, thus increasing the risk of diabetes complications (21).

Anti-Inflammatory Properties

Acutely and chronically, inflammation is related to a variety of diseases such as metabolic syndrome, cardiovascular disease, arthritis, or Alzheimer’s disease. Green tea has been shown to reduce inflammatory response by blocking NF-kappaB activation at many different levels. In animal models, it suppresses proinflammatory gene expression through inhibition of IκB kinase (IKK), preventing NF-κB activation (1).


Prevention Of Parkinson’s Disease 

Polyphenols present in green tea inhibit the formation of neurotoxins called oligomers that are known to cause cellular death in brain cells. It also induces the activity of an enzyme called superoxide dismutase, which is used by the body to produce glutathione (GSH), a natural antioxidant that works against oxidative stress and the resulting damage caused due to free radicals. GSH depletion has been implicated in Parkinson’s disease (18).

Enhancement Of Exercise Performance

Green tea contains caffeine which provides mild stimulation without making you too jittery or nervous. This can help athletes push harder for longer durations as it boosts fat oxidation during exercise, thus allowing them to train harder and longer (13).


People who regularly drink green tea have a lower risk of dying from any cause. The antioxidant properties in green tea reduce free radical damage and oxidative stress, which is believed to be a major cause of chronic diseases, including neurodegenerative diseases and cancer (2).


Green Tea Side Effects

Despite having positive impact on health, green tea has following side effects:

Caffeine In Green Tea

The caffeine content in green tea can be high enough to cause problems for people who are sensitive to caffeine. Even if you’re not sensitive to the effects of caffeine, it may still make sense to limit yourself to three cups per day — or less — so you don’t experience the jittery feeling. 

It can be tempting to drink a lot of green tea when you’re under stress, but the caffeine in it can make your anxiety worse. Drinking too much-caffeinated tea may cause your body’s adrenal glands to produce more cortisol, a hormone associated with long-term stress and elevated blood sugar levels (6). 

For those who have trouble sleeping, drinking a lot of caffeinated tea can make it harder to fall and stay asleep. It also means that you’ll tend to wake up feeling less refreshed and more tired than you would if you let yourself get all the sleep that your body needs each night (11). 

That’s not all! Caffeine is also addictive (5). While it’s not as addictive as some other substances, people can develop a strong craving for the stimulant when they have been drinking too much-caffeinated tea over an extended period. 

In addition to being addictive, caffeine has been associated with wide-ranging health issues, including increased levels of certain stress hormones in the body, depression and anxiety disorders, premature aging, and low bone mass. It may even increase blood pressure and decrease immune function (23).

If you’re going to drink green tea regularly, it makes sense to learn how much caffeine is in it so that you can moderate your consumption to avoid any problems associated with large amounts of caffeine. 

In general, to get the biggest benefits and the fewest side effects from green tea, you should limit your intake to no more than a cup or two per day. You may want to start with just half a cup and assess how that affects you before deciding whether you can safely drink more.

Read More: Is Matcha Or Green Tea Better For Weight Loss? Breaking Down The Differences

facts about green tea

Liver Issues

For people who already have liver damage due to alcohol consumption or hepatitis C, using green tea can exacerbate their existing problems. This is because the compounds found in green tea called catechins can interfere with two enzymes involved in metabolizing alcohol – CYP2E1 and ADH (3). 

This interference can cause additional stress on the liver, which is already working overtime to detoxify the body in these conditions.

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See also  Hibiscus Tea Facts, Health Benefits And Side Effects

facts about green tea

Anemia And Iron Deficiency 

Iron deficiency is a common problem worldwide, especially in women. Some research has suggested that the high tannin content of green tea can lower iron absorption (15). 

While there are many sources of iron found in both plant and animal-based foods (and even fortified processed foods), green tea could exacerbate an existing iron deficiency by further reducing the amount of available iron for red blood cell formation. That’s because it inhibited dietary nonheme-iron absorption, the type of iron found in plant foods, which is not as easily absorbed as heme-iron from meat sources (16). 

Drinking more than four cups of green tea per day for longer than this could lead to iron deficiency anemia, a condition in which the body doesn’t have enough red blood cells due to a lack of iron.

Miscarriage Risk

Due to the high caffeine content in green tea, it’s not safe for pregnant women. This is because caffeine can stimulate the uterus and cause contractions. This may increase the risk of miscarriage or other problems like premature labor (5). 

Additionally, some research has found that drinking large amounts of caffeine is associated with low birth weight infants in mothers who are already considered at risk for preterm delivery (17). This suggests that consuming too much caffeine during pregnancy could put your baby at risk for health problems later in life due to inadequate fetal development.

Scientists are still looking into links between caffeine consumption during pregnancy and low birth weight, however, it’s best to be on the safe side until more is known about any potential risks associated with pregnancies that might occur while drinking green tea every day.

facts about green tea

Birth Control Effectiveness

Using birth control pills, the contraceptive patch, or the vaginal ring? Drinking too much green tea could potentially cause side effects with these methods. The tannins in green tea can decrease the effectiveness of some hormonal contraception by increasing the required dosage of estrogen and/or progesterone needed to maintain a pregnancy (4). 

Catechins in green tea have also been found to reduce levels of testosterone in men, which can lower libido and contribute to impotence-type symptoms. 

Bleeding Disorders

In rare cases, green tea has been found to cause liver problems in people with hemochromatosis, a rare genetic disorder that causes the body to absorb too much iron. Heavy tea drinkers with this condition have had an increased risk of chronic liver disease and cirrhosis (14). If you’re at risk for this condition, avoid green tea consumption altogether. 

Similarly, catechins in green tea could also interfere with the activity of platelets that are necessary for blood clotting. Avoiding or limiting green tea consumption if you frequently use over-the-counter pain medicine like ibuprofen or acetaminophen may prevent interference with platelet aggregation and reduce your risk of excessive bleeding during surgical procedures.

Heartburn And GERD

Drinking too much green tea also has been associated with heartburn, acid reflux, and gastroesophageal reflux disease (GERD). This is likely due to its caffeine content. Caffeine relaxes the lower esophageal sphincter muscle, which separates the stomach from the esophagus. This may contribute to an increased risk of acid regurgitation into the esophagus and symptoms for people diagnosed with GERD (9).

Read More: Tea That Makes You Lose Weight: Health Benefits And Side Effects

facts about green tea

How Much Green Tea Should You Drink?

If you’re very sensitive to caffeine, be sure to limit yourself to a cup of two a day.

If you are pregnant or breastfeeding, limit your daily intake of green tea to four cups per day. Drinking more than that can cause problems for your unborn child or your baby (10). 

If you aren’t sensitive to caffeine, you can drink up to four cups a day. 

For weight loss, it’s best to drink a cup of green tea in the morning before you eat. Doing this significantly increases your metabolic rate during the day, especially if you don’t have any caffeine after noon.

If you’re taking certain medicines, check with your doctor first before adding green tea into your diet. Some of the medicines that you could interact with include blood thinners, potassium supplements, or salt substitutes containing potassium. 

If you are taking medication that lowers your blood pressure, you can drink camomile tea instead of green tea. Camomile has lower levels of caffeine than green tea.


Often with foods and beverages that carry benefits, as well as risks, it’s safest and most sensible to drink them in moderation. Drinking a cup or two of green tea per day shouldn’t cause problems for most people. If you find that more than this upsets your stomach, interferes with sleep, or exacerbates existing medical conditions such as GERD, consider limiting your consumption accordingly.



This article is intended for general informational purposes only and does not address individual circumstances. It is not a substitute for professional advice or help and should not be relied on to make decisions of any kind. Any action you take upon the information presented in this article is strictly at your own risk and responsibility!


  1. An Update on the Health Benefits of Green Tea (2016,
  2. Beneficial effects of green tea: A literature review – Chinese Medicine (2010,
  3. Brewing thoughts: green tea and liver injury (2020,
  4. Caffeine, Oral Contraceptives, and Over-the-Counter Drugs-Reply (1989,
  5. Caffeine and Miscarriage Risk (2008,
  6. Caffeine Stimulation of Cortisol Secretion Across the Waking Hours in Relation to Caffeine Intake Levels (2008,
  7. Caffeine Use Disorder: A Comprehensive Review and Research Agenda (2013,
  8. Camellia sinensis (Tea): Implications and role in preventing dental decay (2013,
  9. Effect of decaffeination of coffee or tea on gastro-oesophageal reflux (1994,
  10. Effect of the consumption of green tea extract during pregnancy and lactation on metabolism of mothers and 28d-old offspring | Scientific Reports (2018,
  11. Effects of caffeine on sleep quality and daytime functioning (2018,
  12. Green Tea Catechins and Cardiovascular Health: An Update (2009,
  13. Green Tea Catechins and Sport Performance – Antioxidants in Sport Nutrition (2015,
  14. Hemochromatosis – StatPearls (2021,
  15. Impact of Tannin Consumption on Iron Bioavailability and Status: A Narrative Review (2017,
  16. Iron deficiency anemia due to excessive green tea drinking (2016,
  17. Maternal caffeine intake during pregnancy is associated with risk of low birth weight: a systematic review and dose-response meta-analysis (2014,
  18. Neuroprotective Properties of Green Tea (Camellia sinensis) in Parkinson’s Disease: A Review (2020,
  19. Protective Mechanisms of Green Tea Polyphenols in Skin (2012,
  20. Skeletal fluorosis in relation to drinking water in rural areas of West Azerbaijan, Iran | Scientific Reports (2017,
  21. The Effects of Green Tea on Obesity and Type 2 Diabetes (2013,
  22. The effects of green tea on weight loss and weight maintenance: a meta-analysis | International Journal of Obesity (2009,
  23. The Safety of Ingested Caffeine: A Comprehensive Review (2017,

Zindzy is a freelance writer who specializes in creating web content in the health & wellness niche. The articles she writes focus on providing factual information – but never at the expense of providing an entertaining read.
Her interest in health & wellness was sparked by her motherhood journey. She realized just how much damage misinformation could cause, especially when it is targeted at new moms who are keen on postpartum weight loss.
So for years, she has worked hard to demystify the seemingly complex concepts of health & wellness. Eventually, she made one startling discovery that she wishes to share with all – there is no short cut. Consistency and hard work are the keys to a healthy mind and body.
But, writing is not all she does. Being a mother to an energetic toddler means her free time is spent exploring the outdoors, arms laden with cotton candy and toys. Through the daily intrigues of work and play, she continues to discover and share more ways to keep fit and stay healthy!

J. Paul

Jovial is from Dubai, and is a Head EMS Instructor/Fitness Manager/Nutrition Consultant for REMS Fitness. He is certified by the Gold’s Gym Fitness Institute and Registered as a Gym Instructor.
Jovial specialises in HIIT training, Rehabilitation/injury recovery, Strength and Conditioning, Kickboxing, Body Weight Training and Weight Training, and practices each discipline himself. His approach is to focus on improving his clients’ lifestyle by motivating them and setting an example.

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