9 Side Effects of Green Tea

Green tea has been a popular choice of beverage for centuries, particularly in East Asia. With an estimated 2 billion cups being consumed daily, its purported health benefits have made it widely accessible around the world. However, one should not overlook the potential side effects associated with drinking green tea.

The primary ingredients are caffeine and polyphenols; both of which can cause adverse reactions if over-consumed such as insomnia, heartburn, or nausea. Additionally, those who suffer from iron deficiency anemia should be aware that components found within the drink may reduce the absorption rates of dietary iron.

Lastly, pregnant women and those trying to conceive should limit their intake due to high levels of caffeine potentially leading to miscarriage or birth defects. It is important to remember that while there are many potential health benefits linked to consuming moderate amounts of green tea regularly, care must be taken to be mindful of any potential side effects that might occur.

green tea side effects

Definition Of Green Tea

Green tea is an ancient Chinese beverage, made from the leaves of Camellia sinensis. This plant species contains numerous varieties of green and black teas, which have become popular due to their potential health benefits. The leaves are typically dried and then either steamed or pan-fired before they are ground into a powder. Green tea has been consumed in China for centuries, but it has recently gained popularity around the world.

The definition of green tea varies depending on its production process.

Generally speaking, green tea is any type of unfermented tea that comes from Camellia sinensis. It may be classified as either ‘true’ green tea or herbal infusions based on how it was produced and prepared. True green teas undergo minimal oxidation during processing and retain more natural antioxidants than other types of teas such as oolong or black tea. Herbal infusions usually contain only herbs or fruit extracts instead of actual leaf material and do not come from the Camellia sinensis plant species. Thus, these are not technically considered true teas.

Green tea leaves can vary in size, shape, color, aroma, flavor, and caffeine content depending on where they were grown and how they were processed; however, all green teas share some common characteristics such as being light-bodied with vegetal notes and having higher levels of polyphenols compared to other types of teas. These polyphenols, which are found in abundance in green teas, are known to have antioxidant properties and may even offer some health benefits.

Health Benefits

Green tea is well known for its many health benefits. It is packed full of antioxidants, minerals, and vitamins which can aid in weight loss, reducing the risk of diabetes and certain forms of cancer, lowering cholesterol levels, decreasing inflammation within the body, and promoting healthy digestion and immunity. 

  1. Weight Loss: Green tea aids in weight loss by increasing metabolism and burning fat. The caffeine content found in green tea helps to boost energy levels while providing a feeling of satiety.
  2. Diabetes: Studies have shown that drinking 4-5 cups of green tea daily can reduce the risk of developing type 2 diabetes. This is attributed to the catechin compounds found in green tea which help improve insulin sensitivity.
  3. Cancer Prevention: Regular consumption of green tea has been linked with a lower risk of developing certain types of cancers such as breast, prostate, and colorectal cancer due to its antioxidant activity.
  4. Cholesterol: Catechins in green tea is known to increase good (HDL) cholesterol levels while at the same time reducing bad (LDL) cholesterol levels.
  5. Inflammation: Green tea contains anti-inflammatory properties which can assist in reducing inflammation associated with arthritis, asthma, and other inflammatory conditions.
  6. Digestion & Immunity: Green tea also provides digestive support and helps promote a strong immune system. It does this by destroying harmful bacteria in the gut and promoting beneficial bacteria growth.

Potential Risks

Green tea has been consumed for centuries and is believed to provide many health benefits. However, like any food or beverage, there are potential risks associated with drinking green tea.

  1. Excess consumption of green tea can lead to health problems such as increased blood pressure, heart risks, stroke risk, kidney damage, and digestive issues.
  2. Adverse reactions may occur due to the presence of caffeine in green tea – symptoms include headaches, insomnia, jitters, irritability, and dizziness.
  3. Long-term effects from consuming large amounts of green tea have not been researched extensively; however, it is known that high doses of catechins (antioxidants found in green tea) can cause liver damage over time.
  4. People who take certain medications should talk to their doctor before regularly drinking green tea because some components can interfere with the absorption of these drugs into the bloodstream.

It is important for people considering adding this drink to their diet to be aware of both its potential benefits and potential risks so they can make an informed decision on whether it’s right for them or not.

Types Of Side Effects

 Some common side effects may include:

Digestive discomfort: caffeine present in green tea can irritate digestive systems if consumed in high amounts. Caffeine-sensitive individuals should be aware of this risk.

Interactions with medications: catechins and other antioxidants found in green tea can cause interactions when taken alongside certain medications.

Allergic reactions: some people may be allergic to tannin or polyphenols present in green tea.

Anemia risks: oxalic acid in green tea inhibits iron absorption and leads to anemia in extreme cases.

Liver toxicity: excessive consumption of green tea extract supplements can lead to liver toxicity.

B vitamin depletion: regular consumption of green tea supplements can deplete b vitamins over time.

Nervousness symptoms sleep difficulties and cardiovascular problems: these are rare but have been reported as minor side effects by users.

It’s important to note that most consumers do not experience any adverse reactions from drinking moderate amounts of brewed green tea; however, it is advisable to pay attention to individual body responses and adjust intake accordingly if issues arise.

(1) Digestive Distress

The consumption of green tea can bring about digestive distress in some individuals.

Green tea has been shown to cause stomach upset, nausea, and other forms of digestive issues. This is likely due to the tannins present in green tea which can irritate the lining of the digestive tract.

A study conducted on mice found those administered high doses of polyphenols from green tea extract experienced significant inflammation in their gastrointestinal systems compared to control groups who did not consume green tea polyphenols. Additionally, caffeine itself may also be a contributing factor for causing digestive distress as it increases acid production in the stomach leading to symptoms such as heartburn or indigestion.

Therefore, people with sensitive digestion should be aware that consuming large amounts of green tea may aggravate existing conditions or induce new ones such as abdominal pain or discomfort, bloating, diarrhea, and constipation. In cases where these symptoms become regular after drinking green tea, it is recommended to reduce or avoid intake altogether until further medical advice can be sought.

(2) Caffeine Sensitivity

Caffeine sensitivity is a condition in which individuals experience adverse reactions from the consumption of caffeine, usually found in products such as coffee, tea, and energy drinks.

Green tea contains varying levels of caffeine, with one eight-ounce cup having around forty milligrams. People sensitive to this substance may suffer symptoms including headaches, jitteriness, and increased heart rate.

Genetics plays a role for some people but other factors like age, weight and other medical conditions can also be involved. Treatment generally consists of managing exposure levels or avoiding it altogether. Physicians may suggest lifestyle changes such as reducing intake, eliminating caffeine or practice,icing relaxation techniques like yoga or meditation. Diagnosis is done through physical examination and blood tests to confirm any potential health issues that could cause similar symptoms.

For those with sensitivities, consulting a doctor before consuming green tea or any caffeinated beverage is recommended. Testing can identify existing sensitivities and help determine safe levels of exposure. Knowing how different forms of caffeine affect each individual will allow everyone to make informed decisions about their dietary habits.

(3) Interactions With Medications

Green tea can interact with several medications, which may cause a variety of side effects. It is important to discuss potential interactions between green tea and other drugs with your doctor or pharmacist before consuming this beverage.

Drug Interaction level Effect
Warfarin Moderate Inhibits metabolism of warfarin
Digoxin Moderate Increases serum levels of digoxin
Theophylline Moderate Decreases theophylline absorption
Antidepressants Mild Enhances drug action

Green tea may interact with certain medications; for example, it can decrease the effectiveness of warfarin and increase serum levels of digoxin. Additionally, consuming green tea with theophylline lowers its absorption while mild interaction occurs when taking antidepressant meds like fluoxetine and paroxetine. Therefore, one should be aware of these potential interactions before drinking green tea while taking medicine.

(4) Possible Allergies

Although green tea is generally considered safe, it can cause an allergic reaction in some individuals.

Green tea allergy symptoms vary among people but may include sneezing and a stuffy or runny nose, nasal congestion, coughing and wheezing, itching of the throat, face, or tongue, and hives. In more severe cases, patients may experience asthma-like symptoms such as difficulty breathing. A rare symptom of green tea allergy is anaphylaxis, which causes a rapid drop in blood pressure that can be life-threatening if not treated quickly.

A skin rash is another potential symptom of green tea allergy; it appears when histamine is released due to contact with the allergen. Tea allergy rash usually manifests itself within minutes of exposure and consists of raised welts on the skin along with redness and itchiness.

To diagnose this type of allergy accurately, doctors will ask about the patient’s history including any past reactions to green tea drinks or food products containing green tea extract. Allergy testing may also be carried out through skin prick tests or patch tests involving small doses of different allergens placed directly onto the skin for observation over time.

Treatment for a green tea allergy includes avoidance of anything containing the allergen as well as antihistamines and corticosteroids to reduce inflammation caused by an immune system response. For those suffering from serious respiratory issues related to their allergies, bronchodilators are sometimes prescribed to open up airways allowing easier breathing.

(5) Iron Deficiency Anemia

Iron deficiency anemia is a medical condition caused by inadequate iron in the body.

It can be associated with drinking green tea, as it may reduce the absorption of non-heme iron found in plant-based foods.

Symptoms include tiredness and fatigue, weakness, pale skin, shortness of breath, dizziness or lightheadedness, headaches, cold hands and feet, and brittle nails. Diagnosis is usually done through physical examination and blood tests to measure hemoglobin levels.

Treatment of this type of anemia includes increasing dietary intake of iron-rich foods such as red meat and dark leafy greens; avoiding drinks that contain caffeine like coffee or soda; taking prescribed iron supplements; and receiving injections of vitamin B12 if necessary.

Prevention involves eating a balanced diet with enough sources of iron as well as monitoring hemoglobin levels regularly when consuming green tea daily. Furthermore, pregnant women should consult their doctor before drinking any kind of tea during pregnancy due to its potential effects on fetal development.

(6) Liver Damage

Green tea has long been used as a herbal remedy in Asian medicine; however, studies suggest that it can be toxic to the liver when consumed in large quantities.

High doses of green tea have been linked with oxidative stress and even cirrhosis. Therefore, authorities advise limiting consumption or avoiding altogether for those at risk. Understanding how much is safe to drink without endangering health is crucial.

Always seek medical advice before making decisions regarding diet and lifestyle habits involving potentially harmful substances like green tea.

(7) Vitamin B Deficiencies

Green tea contains valuable vitamins and nutrients, but it does not contain any of the B vitamins. This lack of dietary sources for vitamin B can put individuals at risk for a deficiency if green tea is consumed excessively or exclusively.

The most common vitamin B deficiencies associated with excessive consumption of green tea are:

  1. Low levels of Vitamin B12, which may lead to anemia;
  2. Impaired absorption issues due to tannins found in green tea inhibiting the body’s ability to absorb certain minerals;
  3. Deficiencies in Vitamin B6, leading to fatigue symptoms; and
  4. An overall low intake of all eight essential members of the B-complex family.

When this occurs, supplementation is recommended through dietary changes or additional supplements as needed.

Increasing one’s intake of other dietary sources such as eggs, poultry, seafood, dairy products, and fortified cereals that provide these important vitamins and minerals will help reduce the risk of a deficiency caused by drinking too much green tea alone.

(8) Sleep Disruption

Green tea is a popular beverage with potential health benefits, however, it can also affect sleep.

Research suggests that due to its caffeine content, drinking green tea before bed could lead to difficulty falling asleep or reduced sleeping time. Additionally, regular consumption of green tea could cause unrefreshing sleep quality and frequent waking up throughout the night.

High doses of caffeine from green tea may also result in daytime fatigue and sleepiness when consumed during the day, leading to difficulty staying asleep at night and waking up too early. Depending on individual sensitivity towards caffeine, green tea could improve cognitive functioning while suppressing appetite but still impact sleep.

It appears that there are clear links between regular consumption of green tea and disrupted sleep patterns, such as insomnia, difficulty falling asleep and staying asleep, as well as short sleeping time resulting in excessive daytime fatigue or sleepiness. Therefore, those who drink green tea frequently should be mindful of these possible side effects and take preventative measures if necessary.

(9) Pregnancy And Lactation

Moving on, it is important to consider the effects of green tea during pregnancy and lactation. It has been suggested that women who are pregnant or nursing should limit their intake of green tea due to potential health risks for both mother and child.

Green tea contains caffeine, which may hurt fetal development when consumed in high doses. Studies have also found that drinking large amounts of green tea while breastfeeding can affect the quality and quantity of a mother’s milk, as well as infant nutrition.

In light of these findings, caution is advised for pregnant or nursing mothers considering consuming green tea products. Although no reports are linking moderate consumption with birth defects or other adverse outcomes, further research needs to be conducted to determine safe levels during pregnancy and lactation.

Until then, if expecting mothers or those who are currently breastfeeding wish to consume green tea they should consult with their physician before doing so.


Green tea is a popular beverage with potential health benefits but can cause side effects in excess or for those who are sensitive to its compounds. Digestive discomfort, nervousness, sleep disruption, cardiovascular issues, and pregnancy/lactation risks can occur.

Anyone thinking of drinking large amounts should speak with their doctor first; preexisting conditions like heart disease might require lower consumption or monitoring due to interactions between green tea ingredients and medications.

Not everyone will experience these negative reactions, so individuals must consult their healthcare provider before making changes. Overall, green tea has many positive attributes, yet it’s important to be cautious when adding large amounts to the diet.

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