For more details on this topic, see deuterium. A deuterium atom contains one proton, one neutron, and one electron. 2H (atomic mass 2.013553212724(78) u), the other stable hydrogen isotope, is known as deuterium and contains one proton and one neutron in its nucleus.
The caffeine in green tea, especially when taken in large amounts, can worsen diarrhea. Irritable bowel syndrome (IBS) : Green tea contains caffeine. The caffeine in green tea, especially when taken in large amounts, can worsen diarrhea and might worsen symptoms of IBS.
Opt for decaffeinated green tea. Caffeine, when consumed in large doses, causes stomach irritation and nausea. It also makes your stomach lining secrete more acid. The caffeine found in green tea can worsen the symptoms of esophageal reflux, and cause stomach upset. You may want to consider high quality Japanese green tea such as gyokuro.