<s>[INST] Can excessive consumption of diet coke cause severe stomach pain that cannot be diagnosed. Tests have been done to check for complete array of possibilities and now 2 different types of antibiotics have been prescribed and that is not working. Have had a colonoscopy, MRI blood work, prostrate exam and all of these have come back okay. Could the diet coke be causing the problem. I have been drinking them for a long time, I drink at least 6 a day [/INST] Diet Coke contains aspartame, a chemical sweetener that is generally very safe but can have side effects including stomach pain, nausea and diarrhea. Diet Coke also contains caffeine which in large amounts can cause increased bowel motions nausea and pain. 6 Cokes a day sounds like a lot. I would recommend decreasing your intake slowly over a couple of weeks and seeing whether this improves your symptoms.Hope you feel better soon!! </s>