1. Upsets the stomach
The tannins present in the green tea increases stomach acid which may cause stomach ache, nauseous feeling, or cause constipation. Thus, green tea is not consumed on an empty stomach. It is best to drink green tea after a meal or in-between meals. Studies have proven that tea is a potent stimulant of gastric acid, which can be reduced by adding milk and sugar. People with peptic ulcers or acid reflux should not overconsume green tea.