Whenever the food passes through the intestines faster than normal, it results in green stool in form of diarrhea (the time is too short for the bile excreted in small intestine to change the color from green to dark brown).
Green stool can result from eating green food or taking iron supplements.
Abdominal pain like cramping is characteristic for diarrhea.
If he has alternated forms of bowel movements, like periods of diarrhea switched with periods of constipation, or tendency to morning diarrhea followed by constipation, and abdominal pain that is relieved by bowel movements, he should talk with his physician about IBS.
IBS sufferers, sometimes experience urinary symptoms, like frequent and urgent urination.


Best wishes!
Marija