I assume there are some people watching this forum who are experienced travelers. I am an experienced traveler, but I've never figured out how to cope with one travel issue: "irregularity." When I fly overseas, my bowels go into a tizzy. First there is a couple days of constipation, then gross-looking dark stool for a couple days, then - if I'm lucky - normality after about a week. Same thing coming home, although it takes less time to get back to normal. What causes this? Does anyone else experience this? Is there a way to avoid it? Is sit just dehydration from the flight?