1. Obstructing Iron Absorption: Ellagic acid and caffeine in the tea can obstruct the body's absorption of iron.

2. Insomnia: green tea contains caffeine and drinking too much of it may lead to insomnia.

3. Dehydration: green tea has a diuretic effect, too much drinking may lead to dehydration.

4. Oral problems: long-term consumption of green tea may lead to oral problems such as yellowing of teeth and bad breath.

5. Digestive problems: Caffeine, ellagic acid and polyphenols in green tea may cause gastrointestinal discomfort and digestive problems.

In short, green tea is good for the body when consumed in moderation, but excessive consumption may cause health problems. It is recommended to consume 2-3 cups of green tea per day.