What Causes Diarrhea?

If you have diarrhea, that may be all you have. Or, your diarrhea may be a symptom of another illness. Diarrhea has a variety of different causes, some more serious than others. Read about the different types of diarrhea and their causes.

Common Everyday Diarrhea

This causes only one symptom—loose, watery, way-too-frequent stools. Usually, you have no idea what causes it: “Must have been something I ate…” Sometimes that’s right, or at least, part of the answer. The combination of foods, drugs, and stress are often to blame—too much pepperoni pizza and coffee the night before final exams.

But more likely, it’s something you drank. Recent research suggests that a great deal of “runs-of-the-mill” diarrhea is caused by germs in the water supply—a mild version of infectious or traveler’s diarrhea (see below). Recently, scientists at Harvard and the Environmental Protection Agency (EPA) correlated levels of germs and other contaminants (turbidity) in Philadelphia’s water during the early 1990’s, and emergency room visits for diarrhea. Although the water never exceeded EPA turbidity limits, even slight increases in contamination caused jumps in ER visits for diarrhea. Since this study, the EPA has tightened up on turbidity limits. But many U.S. water systems still exceed federal contamination limits from time to time, and you may pay the price in urgent trips to the bathroom.

Turbidity may also explain why you’re prone to diarrhea when you travel around the U.S. “You adjust to the mix of micro-organisms in the water where you live, and they stop bothering you,” Dr. Simons explains, “but when you travel, you encounter a different mix, which may cause problems for a few days until you adjust to the new water.”

Infectious Diarrhea

This is the bane of daycare centers. It’s caused by a large number of viruses and bacteria, Dr. Simons explains, including: Shigella, E. coli, and Salmonella, a frequent cause of food poisoning. The germs spread on little hands that touch contaminated fecal material, then touch food, or other children’s hands, which wind up in their mouths. It’s hard to control because young kids don’t win any awards for personal hygiene. Infectious diarrhea is also quite common in nonindustrialized nations, where it is a major cause of childhood death.

Traveler’s Diarrhea

This is turista, the notorious health hazard of trips to Mexican villages and other places where turbidity standards are much lower than they are in the U.S. Turista can cause several days of sprint-for-the-bathroom urgency, liquid stools, cramps, fatigue, loss of appetite, and abdominal distress that may linger for a week or so after the worst of it has cleared up.

You can develop something similar here in the U.S. if you drink from streams without boiling the water first. Even pristine-looking wilderness streams miles from the nearest paved road can be contaminated with diarrhea-causing germs, notably the protozoans Giardia lamblia Entamoeba histolytica.

Food-intolerance Diarrhea

If your system can’t handle dairy products, or wheat, or other foods, you can develop chronic diarrhea—see Lactose Intolerance, Gluten Intolerance, and Food Intolerances. Or perhaps you react badly to sorbitol, an artificial sweetener found in many sugar-free or low-sugar foods and candies. It’s also an ingredient in some drugs.

Supplement-induced Diarrhea

Do you take high doses of vitamin C when you have a cold? It helps, but it may also cause diarrhea, says Alan Brauer, M.D., director of TotalCare Medical Center in Palo Alto, California, one of the nation’s first clinics to combine mainstream and complementary medicine: “Different people have different vitamin C limits.”

Fruit Juice Diarrhea

Apple juice, anyone? Many parents of infants and toddlers give juices by the gallon, and then spend their days changing diapers. Several studies by Dutch researchers have shown that in childhood diarrhea, the culprit is often a diet high in fruit juices. Many adults also notice bowel looseness after eating lots of fruit.

“Leaky Gut” Diarrhea

If you’re small intestine is healthy, only nutrients your body needs pass into the bloodstream. But if your small intestine gets damaged—by infections, drugs (including alcohol and cigarettes), or food intolerances—other potentially harmful substances pass into the bloodstream: incompletely digested fats, proteins, and carbohydrates, and potentially harmful substances that ought to be eliminated in solid waste.

Leaky gut syndrome has been implicated in chronic diarrhea, inflammatory bowel disease, and chronic fatigue syndrome. Until recently, only naturopaths focused on it. But now mainstream doctors are taking it seriously, notably New York City internist Leo Galland, M.D., who specializes in medical mysteries, and contends that leaky gut syndrome contributes to many of them.

Drug- and Illness-induced Diarrhea

Beyond not making it to the bathroom in time, your major risk from diarrhea is water loss (dehydration). Your body may look solid, but it’s more than 75 percent water, explains Ann Arbor, Michigan, health consultant Robert Cooper, Ph.D. Your colon’s main job is to reabsorb two to four quarts of water a day from solid wastes. Diarrhea disrupts this internal water-reclamation project, which depletes your body of sodium and potassium (electrolytes).

If diarrhea lasts more than a few days, it can affect every system in your body, which is, after all, mostly water. Dehydration is a particular hazard for infants, children, the elderly, and people with chronic illnesses, which is why infectious diarrhea is a major public health problem around the world.

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