Ask the Doctors

Dear Doctor: Are there foods and drinks that can help firm up loose stool, so that there isn't an occasional "surprise" when passing gas? Probiotics haven't helped, and multiple tests have proven negative for anything but chronic inflammation.

Dear Reader: We're glad to hear that your doctor has ruled out a medical cause for your experience with loose stools. And since you haven't referenced diarrhea, we'll assume that's not relevant to the issue you're having.

In many cases, this is the result of something in the diet, so let's start with the basics of digestion.

For the most part, digestion is a "wet" process. Food goes into our mouths and we chew, adding saliva to substances that, to some degree or other, already contain moisture. In the stomach, the chewed food gets further broken down by powerful acids, which deliver a liquid slurry to the small intestine.

Here, digestive juices from the pancreas, liver and intestine finish the dismantling process. The digested nutrients are then absorbed by the walls of the small intestine, where they enter the blood and are delivered to the rest of the body.

As the waste products that are left behind begin to move through the large intestine, the stool is formed. The job of the large intestine is to absorb water from these waste products, along with any stray nutrients. This process changes the waste from a liquid form into the firm mass of the stool. This is then stored in the rectum until a bowel movement occurs.

The upshot is that loose stool is the result of excess water that was not removed by the large intestine. Since illness and infection aren't the cause, let's look at diet.

Dietary sugars, which can increase the absorption of water, may exacerbate loose stools. That's in part because sugar is hygroscopic, which means it attracts and absorbs water. In addition, some people lack adequate enzymes to digest certain sugars. These sugars can include sorbitol, which is found in prunes, peaches and apples; mannitol, which is found in pineapples and asparagus; and xylitol, a sugar present in lettuce and strawberries. Each of these can have a laxative effect. The sugars in wine and beer can cause loose stools, as can lactose, the sugar found in milk products.

Caffeinated beverages, fried foods, fatty meats and additives like MSG and artificial sweeteners can also cause problems. In fact, for many individuals who experience digestive problems, the question may be not what to add to your diet, but what to eliminate from it.

If you're up for it, you might try an addition diet. Start with a small but nutritious range of foods that result in normal bowel movements. Think lean meats, small portions of vegetables, and potassium-rich foods like bananas. Then, one by one, begin to expand the range of foods in your diet. There are probably certain foods that your body absorbs better than others.

By proceeding slowly and keeping a food diary, you may be able to pinpoint the culprits and tailor your diet to your specific needs.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

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