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.
While coffee is unlikely to cause diarrhea, that does not mean it's not a problem for you. At least one small study published in the journal Digestion in 2001 found that coffee was among the most common foods reported to cause symptoms -- including diarrhea -- in people with irritable bowel syndrome (IBS).