Green Tea Side Effects

Green tea is a very healthy beverage and it improves the health of people who drink it regularly in general. However, there are some side effects it can cause, especially when being consumed in very high quantities regularly. Remember, moderation is important with everything in life. That goes for drinking green tea too. In this text we will inform you about possible side effects you may experience from drinking green tea and give you advice on how to avoid or deal with them.

Upset stomach, constipation, and nausea

You can experience nausea, constipation, and an upset stomach if you drink green tea as soon as you wake up on an empty stomach. What seems to cause these are tannins in green tea which instigate higher production of stomach acid.

This is a big problem for people who suffer from ulcer and stomach acid reflux and they should be very careful with green tea consumption and it might be advisable for them to skip it entirely. One way to prevent or reduce nausea, constipation and upset stomach symptoms is to drink green tea only after you had a meal. Another is to add some milk, but that could block some of the beneficial effects of substances found in green tea.

The caffeine effect

Yes, green tea contains caffeine. However, there’s a lot less of it in green tea than there is in black tea or coffee. Still, this is enough to cause some undesirable side effects to some people. Caffeine tolerance and reactions vary from person to person.

There are numerous side effects you may experience: headache, nervousness, insomnia, vomiting, diarrhea, confusion, convulsion, dizziness, heartburn, tremor, irregular heartbeat, irritability… Caffeine can also interfere with the prescribed medication you may be taking.

If you are worried you might have troubles with these, you can try some green tea types which contain less caffeine than most. Some of those are houji-cha, bancha and gyokura.

Anemia (iron deficiency)

Tannins in green tea reduce the amount of iron absorbed in the blood. This is a double-edged blade. It has positive effects on people who have too much iron in their blood, but it has bad effects on people who have too little. So, green tea can sometimes cause anemia.

To minimize risk and this possible negative effect of green tea, only drink it between meals. That way, your body will process most of the iron that comes to your body through food without tannins from green tea being able to interfere. Also, in case you have a low level of iron in your blood, you should do your best to eat as much food rich in iron or food that increases iron absorption as possible. These are red meat and food rich in vitamin C, lemon for example. Lemon is especially convenient because you can add it to your tea as a supplement and it will improve tea’s flavor. Two birds with one stone.

Pregnancy and breastfeeding

In most cases, green tea consumption doesn’t have undesirable side effects on pregnant women or women who still breastfeed. However, there are some cases when they did occur and for that reason, you should always be careful. Some studies have linked green tea consumption in early pregnancy with neural birth defects. To be on the safe side, consult your doctor. Don’t drink more than two cups of green tea a day.

List of health conditions green tea don’t mix well with:

1. osteoporosis
2. liver diseases
3. high blood pressure
4. irritable bowels
5. glaucoma
6. diarrhea
7. diabetes
8. heart problems
9. bleeding disorders
10. anxiety disorders
11. anemia


If you’re taking prescribed medication, green tea can interfere with its effect. In this case, consult your doctor and consider lowering or entirely eliminating green tea consumption. Another option would be to split taking your medication and drinking green tea in a big-time interval so your body can process them separately.

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How to drink green tea with minimum risk of side effects:

1. Drink it fresh, but slightly cooled
2. Brew the same tea leaves multiple times
3. Avoid high concentrated tea brands
4. Consult your doctor about green tea interference with your medication
5. Moderation! Don’t drink too much of it
6. Drink it at least an hour before or after meals, never back to back with them

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