If you are drinking green tea in normal quantities there are almost no side effects. To the contrary, green tea brings you many health benefits.
However, consuming large amounts of strong green tea can have some harmful effects:
- Green tea can dilute the gastric juices, making it difficult to digest food normally. Worse effects can include dyspepsia, abdominal distension or duodenal ulcer.
- Absorption of iron may be reduced. The stronger the green tea you drink, the greater the resistance to iron absorption in your body. This may be especially harmful to women during their period.
- There is much more tannic acid contained in strong than in weak green tea, which may aggravate symptoms of constipation. This is because tannic acid can slow bowel peristalsis.
- Too much caffeine intake will increase heart rate and elevate blood pressure. It can also cause chest tightness and palpitation.
- Women should avoid excessive consumption of green tea during pregnancy because it normally contains more caffeine than other kinds of tea; however, there is no harm in enjoying one or two cups now and again.
- People who are sensitive to caffeine should avoid green tea because it can exacerbate insomnia, anxiety, irritability, nausea or upset stomach.
- People who take blood thinners such as Coumadin/Warfarin should drink green tea only after seeking their doctor’s advice because these medicines contain vitamin K. Aspirin should also be avoided if drinking green tea because both can reduce the clotting effectiveness of platelets.
- People who are taking stimulant drugs should avoid green tea because of its effect of increasing blood pressure and heart rate.
- People who are taking any medicine should seek their doctor’s advice before drinking green tea.