Photo: Damon Dahlen, AOL

There's nothing sexy about today's topic. But runner's diarrhea (characterized by loose stools that occur during or immediately after a run) affects anywhere from a quarter to a third of runners. Considering the large numbers impacted by it, I find that runners don't talk about it much. I know it's not exactly appropriate water-cooler convo, but the problem is uncomfortable, inconvenient and clearly pervasive.

"Many races are lost in the port a pottie," says Nancy Clark, sports nutritionist and author of "Nancy Clark' s Food Guide for Marathoners." And because you've all trained too hard for too long to let your digestive system dictate your race-day performance, I spoke to Clark to understand the causes of runner's trots and how to treat it.

There's a reason there's no such thing as cyclist's trots. "It's the jostling of the intestines during running that stimulates motility," says Clark. Cycling and other exercises, where the body is stable, don't have the same effect running does. Of course, not everyone who runs will have stomach trouble. "People have different sensitivities in their digestive tracts and we're all metabolically individual. It's similar to how some people are wired all day after a cup of coffee and others aren't." Also at risk for diarrhea from running are new runners and women, whose hormonal fluctuations make them more susceptible.

"When someone comes to me complaining of this issue, the first thing I do is look to see if they're eating too much fiber," Clark says. When you have bran cereal for breakfast, wheat bread with lunch and brown rice with dinner, you might be overdoing it and a subtle shift in fiber consumption could make the difference. The best place to trim fiber is in your cereal. "The biggest dose of fiber tends to come from bran cereals like Kashi, All Bran and Raisin Bran in the morning."

Another consideration is what you're eating during your runs. For many, it's the engineered foods they consume while they're running that gives them "instant diarrhea," says Clark. Instead of gels, try gummy bears, honey sticks or dried apricots. These foods might prove easier on your stomach. For some, it's not the gel itself, but the quantity. "One gel might be fine, 10 might not," she says.

It seems counterintuitive, but dehydration is also a culprit. Be sure to drink enough to quench your thirst. Start drinking either water or a sports drink from the beginning of the event, to prevent yourself from becoming dehydrated, suggests Clark.

Some other strategies that might help include taking an anti-diarrheal medicine an hour before you run, avoiding diet sodas and foods and drinks that contain sorbitol, not eating within three hours of a run and avoiding fiber in your pre-run snack. Once you've suffered a bout of the runs, replenish with a mix of liquid and salt. Chicken noodle soup, pretzels and ginger ale are good options that are easy on the tummy, says Clark.

If you're suffering from diarrhea and can't pinpoint the cause, your best bet is to write down what you're eating, when you're eating, when diarrhea happens and how bad it is for several days. Then pay a visit to a gastroenterologist and you'll already be armed with some important data.

There's no reason to accept diarrhea as an unavoidable part of long-distance running. Know that there are strategies that can help.

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