These days doctors are diagnosing an increasing number of cases of celiac disease— autoimmune disorder whose symptoms are triggered by gluten, the protein content in wheat, barley, rye, and spelt—in recent years. But a growing number of the people dodging gluten fall into a gray area: they don't have celiac disease but seem to be unable to digest gluten properly.
There are no tests or strict criteria for this problem, aside from simple trial and error with a gluten-free diet. Some people may be getting caught up in a food fad. But many others probably do have a real problem digesting gluten or perhaps the sugars in some of these grains.
There's a third group of gluten-free converts: people who are blaming gluten for a wide range of medical conditions, not just gastrointestinal distress. For example, there's a fairly loud Internet "buzz" about autistic children improving once they're on a gluten-free diet.
Based on what is currently known, it's a big leap to attribute autism and other problems to gluten, and an even bigger one to prescribe gluten-free eating as a treatment.
Misreading the situation
Gluten is an imprecise term that shifts meaning depending on the context. In the context of celiac disease, gluten refers to the protein of grains capable of provoking an autoimmune response. Other grains also contain protein, but wheat, barley, rye, and spelt contain varieties that aren't broken down by digestive enzymes.
These proteins don't faze the guts of most of us. But in people with celiac disease, when they get absorbed into the walls of the small intestine, the immune system misreads the situation, views them as intruders, and unleashes a furious inflammatory response that damages tissue. The inside of a normal, healthy small intestine is carpeted with millions of fingerlike projections called villi that produce digestive enzymes and soak up nutrients. The misguided immune response triggered by the gluten proteins sometimes attacks these villi. When that happens, the villi produce fewer digestive enzymes and absorb fewer nutrients.
Symptoms — classic and non
The classic and most immediately noticeable symptoms of celiac disease are, not surprisingly, gastrointestinal: bloating, flatulence, and diarrhea, sometimes with smelly stools. People who can't digest gluten or grain sugars may have similar symptoms.
Celiac disease can severely impair the absorption of nutrients. In children, this may lead to stunted growth; in adults, the consequences include anemia (because iron isn't being absorbed) and weaker bones (because calcium and vitamin D aren't getting into the body). Anemia causes fatigue and malaise, but some people with celiac disease feel that way without anemia.
One major difference between celiac disease and grain-related digestion problems is that when it's just a digestion problem it typically doesn't lead to malabsorption and nutritional deficiencies.
A blood test and a biopsy
The diagnosis of celiac disease begins with a blood test for the antibodies generated by the immune response that gluten provokes. If the blood test is positive, the next step is biopsy of tissue from the small intestine to see if the villi have been damaged. Collecting the biopsy involves snaking an endoscope down the throat and through the digestive tract and snipping out small pieces of tissue that can be examined under a microscope.
The super six
We're often too quick to depend on pills instead of first working to change our diet and exercise habits. But with celiac disease, there's no pill, and a fairly radical change in diet is the only treatment. Drug companies have started to take some interest in the disease, and treatments that would block the absorption of gluten are being investigated, but none so far are close to gaining FDA approval.
Gluten-free eating is a two-way street: getting the gluten out while bringing in healthful — and palatable — alternatives. Some foods are obviously made with wheat and the other gluten-containing grains. Conventional bread, bagels, pizza — they're out if you have celiac disease. But until you need to avoid gluten, you probably don't realize how ubiquitous it is. Gluten is used as a thickening agent and filler in everything from ketchup to ice cream. The inactive ingredients in many medications are gluten-based. And even when gluten isn't an ingredient, it may inadvertently get into a food because a wheat-based food was processed in the same factory, or wheat was grown in a nearby farm field.
The gluten-free diet has traditionally depended on starch from rice, corn, and potatoes. Food makers have also learned how to use xanthan and guar gums to replace gluten's elasticity: a common complaint about gluten-free baked goods is that they are powdery. But these formulations can also leave diets short of fiber and B vitamins. Melinda Dennis, the nutrition coordinator at the Beth Israel Deaconess Medical Center Celiac Center, encourages patients to eat foods made with unconventional but nutritionally well-rounded substitutes, including amaranth, buckwheat (no relation to wheat), millet, quinoa, sorghum, and teff. She calls them the "super six" because of their high vitamin and fiber content.
July 2009 update