Green tea is very helpful to maintain fitness 50 ml to 70 ml is sufficient alone green tea won't work, daily exercise and diet control is also needed to maintain health side effects. Are these side effects can range from mild to serious and include headache, nervousness, sleep problems, vomiting, diarrhea, irritability, irregular heartbeat, tremor, heartburn, dizziness, ringing in the ears, convulsions, and confusion. Green tea seems to reduce the absorption of iron from food.