Between the uber-popular low-carb Dukan Diet and 17-Day Diet, plus the ever-growing aisles of gluten-free items at the grocery store, banishing wheat and gluten seems like a healthful choice.

But should you stop eating wheat and gluten?

Truth is, it depends.

For most people, a gluten-free diet offers no benefits. (Gluten is a protein found in wheat, rye and barley.) In fact, a gluten-free diet may even bring unwanted results, such as nutritional deficiencies. And contrary to popular belief, there's no evidence that a gluten-free diet leads to weight loss, nor is there even a plausible theory for why it would. Even worse for dieters, moving from "regular" processed foods to gluten-free ones may result in weight gain. "Lots of gluten-free products are higher in fat," says Tricia Thompson, M.S., R.D., author of The Gluten-Free Nutrition Guide. "Pretzels, for instance-manufacturers add fat to give them better mouthfeel." (Plus, these pretzels cost four times as much as "regular" ones.)

That said, gluten-free eating performs wonders for one group of people: those who have celiac disease, which is 1 in 133 Americans. And experts estimate that as many as 3 million Americans (about 1 percent of the population) have celiac disease, but only 10 percent have been diagnosed.

What is celiac disease? People with celiac disease can't tolerate gluten. If they eat foods or use products containing gluten, their immune system responds by damaging the lining of the small intestine, where nutrients from food are absorbed. This damage to the small intestine decreases the absorption of all nutrients-resulting in an overall poor nutritional status. If not treated, a person with celiac disease can develop more severe nutritional deficiencies, such as osteoporosis (because of poor calcium absorption), iron-deficiency anemia or multiple other vitamin and mineral deficiencies.

There are also people who may be sensitive to gluten without having celiac disease. This condition, known as "gluten intolerance," isn't well understood: people with gluten intolerance experience symptoms when eating gluten-containing foods and they usually feel better after removing gluten from their diet, but they don't have the damage to their small intestines seen in celiac disease. (Find recipes, expert tips and articles for all you need to know about eating a healthy gluten-free diet here.)

If you are experiencing unexplained gastric distress or other symptoms (irritability, tiredness, weight loss) of celiac disease, you should talk to your doctor before you begin eliminating all gluten-containing foods. Your doctor should first determine whether you have celiac disease or whether your symptoms are caused by some other food intolerance or allergy. You'll need a full medical workup and, to definitively diagnose celiac disease, a blood test and a biopsy of the small intestine.

Of all the misconceptions about gluten-free diets, the most dangerous is that you can self-diagnose celiac disease. If you go gluten-free, the antibodies (created when a person with celiac disease consumes gluten) that doctors screen for in the blood disappear. You may need to go back to eating gluten for several months to be properly tested.