Although in future weeks I will devote considerably more space to traveler's diarrhea (ciguatera, E. coli, giardiasis, and Salmonella), the fact is, more travelers have a problem with constipation--especially if they take Lomotil or Pepto-Bismol prophylactically to prevent diarrhea.
Constipation can literally ruin a trip, so here's what you can do:
First of all, don't use medicines for diarrhea unless you actually have diarrhea. The flushing action of the condition removes the disease-causing organisms from your system, and a little bout of diarrhea is usually best untreated (except for hydration).
If you have had a heart attack or stroke, or if you have uncontrolled high blood pressure or a hernia needing repair, it's better to treat constipation with stool softeners like Surfak rather than with bulking agents.
Exercise helps you get more regular, but only a little more regular. The equivalent of walking 3 miles (5 km) a day is about the maximum for constipation relief. (There are, of course, many other benefits of exercise!)
Never use both a fiber supplement and a stimulant laxative for constipation at the same time.Be careful about treating constipation with bran. If you eat bran cereal for your last meal of the day, it will help "scrub" your colon. If you eat bran for a late breakfast and then have an early lunch, the intestines do not have a chance to evacuate the bran and it can cause bloating, gassiness, and even more constipation.
And, in general, you can relieve constipation by eating smaller meals. Less food at any single meal gives the lower digestive tract more time to move it out.