Medical Edge Newspaper Column

Preventing Diarrhea

June 10, 2007
Dear Mayo Clinic:
I am a 48-year old woman who has the sudden onset (within a half-hour) of uncontrollable watery diarrhea after eating in restaurants. I'm trying to narrow down the cause and believe it's either greasy foods or the lettuce in salad bars. I've eaten at the same restaurants and eaten the same foods, but sometimes it happens and sometimes it doesn't. I'm to the point where I'm afraid to eat out. What could be causing this embarrassing problem?

Answer:
I assume that you don't have any alarming symptoms along with the bouts of diarrhea, such as fever, bleeding, or weight loss. If you do, please see a doctor.

Otherwise, the watery stools may have many possible causes that are relatively benign. Some are associated with meals, while others are independent of what you eat, though particular foods may exacerbate the effects of such conditions. Irritable bowel syndrome is perhaps the most common cause of diarrhea, but it would likely be accompanied by abdominal pain and other symptoms, which you do not report.

Similarly, food poisoning is a cause of diarrhea — lettuce in salad bars, one of your suspects, could be tainted with problematic bacteria or other infectious organisms — but it would take hours, not minutes, for that reaction to occur. And it would be unlikely to recur over time.

The speed of response in your case points to two leading candidates: dumping, and an exaggerated gastrocolic reflex. In dumping, food simply leaves the stomach too fast. This is prompted not so much by foods as by fluids, especially liquids such as pop, juice, or milk shakes. The individual can also experience pain, sweating, and even wooziness.

Alternatively, your problem might be an exaggerated gastrocolic reflex: a neural impulse, prompted by particular foods, in which an electrical signal sent from the stomach to the colon causes it to undergo a high-pressure contraction. The resulting wave agitates waste material already in the intestines, expelling it before the intestinal walls can do their job of absorbing most of the water. Therefore, stools are watery.

On the assumption that an exaggerated gastrocolic reflex is indeed the problem, you can address it in two ways. One is to systematically identify the food that causes the abnormal response. You have to do this on your own, by trial and error, because no reliable laboratory tests can conveniently do it for you. The process is simple: Refrain from eating suspected foods, one at a time, in descending order of the perceived likelihood of causing an episode of diarrhea.

If this series of experiments fails to identify the culprit, or you prefer to forgo it in the first place (as the process can be long and something of a hassle), the second option is to take an over-the-counter medication before meals that may prevent the diarrhea. Antidiarrheal drugs such as loperamide (Imodium) can slow the colon down, and they have proven themselves over time to be safe and, often, effective. You may need to experiment, though, to find the dose that's right for you, if it exists at all. If this approach works, it's a nice protective option to have when you go out to eat, as long as you don't eat out every night. It's best for occasional use, as antidiarrheal drugs might otherwise cause chronic and pronounced constipation as a side effect.

If neither of these options works, it's time for a medical consultation. Your doctor can prescribe an antispasmodic drug, like hyoscyamine sulfate (NuLev), that might prevent diarrhea , and can also take a medical history, perform an examination, and order tests to see whether some other underlying condition is behind the problem.

Finally, you might consider the possible contribution of stress, either from sometime pressures in your daily life or directly from conditions at the restaurant. It may be so warm or noisy there, for example, as to make you quite uncomfortable. The resulting stress can trigger the exaggerated gastrocolic reflex.

— G. Richard Locke, M.D., Gastroenterology, Mayo Clinic, Rochester, Minn.