Who is Forbidden to Drink Green Tea: Serious Side Effects

Green tea is one of the oldest herbal teas known to man. It gained rapid popularity in India after its supposed health benefits were discovered, as well as an effective tool for weight loss.

Some theories of potential health benefits have a lot of research to support them, and some do not. Because of the positive attention, some of the side effects of green tea are often overlooked. But it is important to understand that green tea also has some health limitations that may directly answer the question: who should not drink green tea?

The tannins present in green tea increase stomach acid, which can cause stomach pain, nausea, or constipation. Thus, green tea should not be consumed on an empty stomach.

Green tea is generally safe for adults if consumed in moderation. However, drinking too much green tea, more than 3 cups per day, is considered dangerous. The side effects of green tea are related to the caffeine present in it, which may include some or all of these symptoms.

Side effects of green tea

  • Mild to severe headache
  • Nervousness
  • Problems with sleep
  • Vomiting
  • Diarrhea
  • Irritability
  • Arrhythmia
  • Tremor
  • Heartburn
  • Dizziness
  • Ringing in the ears
  • Convulsion
  • Confusion

The tannins present in green tea increase the acidity of the stomach, which can cause abdominal pain, nausea, or constipation. Thus, green tea should not be consumed on an empty stomach. It is best to drink green tea after meals or between meals. People with peptic ulcer disease or acid reflux should not consume green tea excessively.

For example, a 1984 study concluded that tea is a powerful stimulant of stomach acid, which can be reduced by adding milk and sugar.

Iron deficiency

Green tea reduces the absorption of iron from food. Consumption of very high doses can be fatal. The lethal dose of caffeine in green tea is estimated at 10-14 grams (150-200 mg per kilogram).

A 2001 study reports that green tea extract reduces the absorption of non-heme iron by 25%. Non-heme iron is the main type of iron in eggs, dairy products, and plant foods such as beans, so drinking green tea with these foods can lead to reduced iron absorption.


Like all teas, green tea contains caffeine. How does green tea affect the heart? Excessive consumption of caffeine can lead to nervousness, anxiety, irregular heart rhythm, and tremors. Some people have a naturally low tolerance to caffeine, and they will suffer from these symptoms even when consuming small amounts of caffeine. High caffeine intake can also interfere with calcium absorption, affecting bone health and increasing the risk of osteoporosis. To prevent caffeine-related problems, limit your green tea consumption to 5 cups or less per day.

Pregnancy and breastfeeding

Who is not allowed to drink green tea? Green tea contains caffeine, catechins, and tannins. All three substances are associated with the risk of pregnancy. If you are pregnant or breastfeeding, green tea in small amounts, about 2 cups per day, is safe. This amount of green tea provides about 200 mg of caffeine. However, consuming more than 2 cups of green tea per day is dangerous and is associated with an increased risk of miscarriage and other negative effects. In addition, caffeine passes into breast milk and can affect the baby. In addition, drinking large amounts of alcohol can cause a birth defect in the neural tube in babies.


Green tea catechins can cause a decrease in iron absorption from food. If you have iron deficiency anemia, the National Cancer Institute recommends drinking tea between meals. If you like to drink green tea with your meals, research shows that you should eat foods that improve iron absorption. Foods high in iron include meat, such as red meat, and foods high in vitamin C, such as lemons.

Anxiety disorders

The caffeine in green tea is said to increase anxiety.

Blood clotting disorders

Caffeine in green tea can increase the risk of bleeding.

Heart disease

Caffeine in green tea can cause irregular heartbeat.


Caffeine in green tea can affect blood sugar control. If you drink green tea and suffer from diabetes, keep a close eye on your blood sugar levels.

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Written by Emma Miller

I am a registered dietitian nutritionist and own a private nutrition practice, where I provide one-on-one nutritional counseling to patients. I specialize in chronic disease prevention/ management, vegan/ vegetarian nutrition, pre-natal/ postpartum nutrition, wellness coaching, medical nutrition therapy, and weight management.

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