Some of the most helpful bacteria are known as probiotics—a word you may have seen on food or beverage labels. Food manufacturers highlight the probiotics in their products because these bacteria help restore or maintain a healthy balance of “friendly” bacteria in the GI tract. Although some manufacturers add probiotics to their products, probiotics are found naturally in fermented foods, such as dairy products like yogurts, buttermilk, and cottage cheese. Other fermented sources of probiotics include soy, tempeh, miso, and sauerkraut.

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A healthy diet should also contain plenty of prebiotics, certain types of nondigestible carbohydrates that healthy bacteria use to boost their growth in the large intestine. (You can think of prebiotics as substances that “feed” or nourish good bacteria.) Eating prebiotics may prevent and treat diarrhea and colon cancer, boost the absorption of minerals, reduce levels of fat in the blood, and help control blood glucose. Some of these benefits may result from the short-chain fatty acids that are produced as bacteria use the prebiotics. These short-chain fatty acids, which are only 3 or 4 carbons in length, are then absorbed and provide us with a little energy, as well. Sources of prebiotics include chicory, Jerusalem artichokes, whole-grain rye, oats, wheat, and barley, leeks, garlic, and onion. Chapter 12 contains more detailed information about both probiotics and prebiotics.

Scanning the prebiotic list above, you’ll notice that some of those foods—rye, wheat, and barley—are damaging for people with celiac disease, since they contain gluten. Not surprisingly, then, people with celiac disease consume fewer prebiotics and therefore tend to have a significantly different mix of bacterial species in their guts than people who can eat gluten-containing prebiotics without problems. Alessio Fasano, MD, director of the Center for Celiac Research at the Massachusetts General Hospital for Children in Boston, recently studied the guts of a small number of infants genetically predisposed to celiac disease and found that the balance of bacteria and their metabolic products shifted just before the infants developed celiac disease. If these results hold up in a larger sample of infants, he says, scientists may have a “crystal ball that predicts when these kids will develop autoimmunity,” allowing doctors to give probiotics or prebiotics that restore the balance of their gut bacteria and perhaps stave off the disorder.

Even though celiac disease does its damage in the small intestine, its effects are felt throughout the body. That’s because the immune cells that start attacking the villi of the small intestine eventually go somewhere else. “Celiac starts in the small intestine, but any organ in the body can be affected,” Fasano says. He has seen patients with celiac disease and no stomach problems, for instance, but who have anemia or damage to the liver. The pancreas can also be damaged by these immune cells, rendering it less able to produce hormones that regulate metabolism, such as insulin.

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