In the trendy world of popular diets, the latest catchphrase is gluten-free. This eating style is absolutely essential for people with celiac disease, who can't tolerate even small amounts of the protein gluten, which is found in grains such as wheat, rye, and barley. As many as two million Americans may have celiac disease, though only 300,000 or so have been diagnosed with it. Many people without celiac disease are also following a gluten-free diet, reports the April 2013 Harvard Health Letter.

"It's a popular diet of the moment, but it really does seem to provide some improvement in gastrointestinal problems for a segment of the population," says Dr. Daniel Leffler, an international authority on celiac disease and an assistant professor at Harvard Medical School.

When a person with celiac disease eats gluten, his or her immune system attacks the lining of the small intestine. The damage that results causes symptoms such as gas, bloating, diarrhea, constipation, headache, trouble concentrating, and fatigue. It can also lead to weight loss and malnutrition. Celiac disease was long believed to be the only condition triggered by gluten. But there is now good evidence that a condition called nonceliac gluten sensitivity causes similar symptoms but no intestinal damage.

The key treatment for both celiac disease and nonceliac gluten sensitivity is cutting gluten out of the diet. But that's more than just a matter of buying gluten-free products in the grocery store and avoiding obvious foods with rye, barley, or wheat—such as bread, cereal, pasta, and pizza. "It takes a long time to learn how to live gluten-free," says Dr. Leffler. You have to become a gluten detective, scouring food labels and looking for hidden gluten. That's because gluten is in everything from frozen vegetables to soy sauce and medications.

Read the full-length article: "Considering a gluten-free diet"