Studies suggest that the best time to drink green tea is in the morning and before the workout session. Swapping your cup of coffee with green tea is the best way to kick start your day. Like coffee, green tea also contains some amount of caffeine and L-theanine.

Green tea can cause side effects due to caffeine. These can include anxiety, tremors, irritability, and sleeping problems. This is more likely if you're sensitive to caffeine or take large doses. Side effects are less common with green tea than with other drinks that have caffeine.

Precautions. Pregnant and breastfeeding women, children under the age of 2 and people with kidney disorders, heart conditions, stomach ulcers and psychological problems should also avoid taking green tea. People with glaucoma, anemia, liver disease, osteoporosis and diabetes should also avoid it.