Gluten is the spongy complex of proteins found in wheat, barley, and rye that allows dough to rise. As yeast ferments sugar and releases carbon dioxide, gluten inflates like a hot air balloon, giving breads and cakes their delectable texture.
According to USA Today, up to one-quarter of all consumers now want gluten-free food, even though only one person in 100 has celiac disease, the autoimmune disorder worsened by gluten ingestion. Going gluten-free seems somewhat faddish. The roster of celebrities who’ve gone temporarily or permanently off it includes Chelsea Clinton, Lady Gaga, Miley Cyrus, Drew Brees, and Oprah Winfrey, among many others.
If only a small fraction of people have celiac disease, why do so many think they need gluten-free foods? It’s tempting to dismiss the phenomenon as the latest hysteria around an over-diagnosed problem. But there is a more nuanced perspective that is more constructive and less judgmental.
To understand the proper role of gluten-free diets requires untangling three separate and unrelated medical problems blamed on gluten: celiac disease, wheat allergy, and gluten intolerance. Here’s the thing: The first problem is almost certainly underdiagnosed, but the latter two are likely to be overdiagnosed.
Celiac disease occurs in some people when fragments of gluten bond with intestinal proteins and provoke a powerful, misdirected immune overreaction from white blood cells. The friendly fire destroys the microscopic fingers called villi that line the small intestine and normally absorb nutrients. Once bombed out, the intestine can’t function correctly, causing symptoms such as belly pain, diarrhea, iron deficiency, and other severe problems. Celiac disease is properly diagnosed with a blood test followed by an endoscopic biopsy of the small intestine to confirm that villi are damaged.
For hundreds of years, doctors had known that some well-fed children still appeared malnourished, and in the first century the condition was named for the Greek word for abdomen, or “koelia.” No one knew what caused it until World War II, when a Dutch pediatrician realized that a grain shortage dramatically lowered the death rate among children with the disorder from 35 percent to zero.
Today, we know that 1 percent of the world’s population has celiac disease—meaning almost 3 million Americans, of whom only a small fraction have been properly diagnosed. Often sufferers go for 10 years before diagnosis, and many physicians are unfamiliar with the signs. In fact, only one-third of primary-care doctors have correctly suspected or diagnosed it. Instead, some patients are incorrectly labeled as having irritable bowel syndrome, eating disorders, or dietary vitamin deficiency. (In one unusual case, a 5-year-old boy thought to have severe autism actually had celiac disease.) The lack of proper diagnosis is one reason advocacy groups think the condition is still underpublicized.
The second kind of problem that can be caused by gluten is wheat allergy. In this condition, a wheat-specific antibody, called an IgE, causes hives, sudden anaphylaxis, sneezing, and wheezing when someone eats gluten. In contrast to celiac disease, true wheat allergy, also called baker’s asthma, is believed to be pretty rare.
One problem with wheat allergy is that there is no good test for it. In fact, the blood tests for IgE (called RAST tests) are notoriously unreliable; for example, only one in eight children with a positive IgE test for peanuts is truly allergic. (In 2008, medical sociologist and physician Nicholas Christakis published a commentary in the British Medical Journal titled, “This allergy hysteria is just nuts.”) Because RAST tests can screen for dozens of possible allergies at once, there is a danger of overdiagnosis, especially when interpreted by nonspecialists.
But the most confusing problems arise with the third problem blamed on gluten: so-called gluten intolerance. This condition is neither an autoimmune disorder, like celiac disease, nor an allergy, like true wheat allergy. There’s not even a mediocre blood test for gluten intolerance. The diagnosis simply relies on someone’s subjective feelings of bloating, bowel changes, or mental fogginess after eating gluten. This is a set-up for all manner of pseudo-scientific self-diagnoses, especially when you consider that 2 percent of people believe they have illnesses caused by magnetic fields.
And yet, a randomized, blinded trial in Italy just showed that one-third of patients with gluten intolerance clearly felt better with gluten-free diets, which confirmed “a distinct clinical condition.” (Since most people can tell wheat-containing baked goods from their gluten-free substitutes, the investigators cleverly had all patients follow gluten-free diets and then take capsules containing either gluten or a placebo.) Another randomized trial published in a reputable journal also showed an improvement in symptoms in some subjects eating a gluten-free diet. Those researchers speculated that sufferers might have a problem not with gluten, but specific sugars called fructans in wheat products.
This is the most frustrating part of gluten intolerance. There are certainly people who have a problem with gluten that’s not autoimmune or allergic. And yet, the data suggest that almost two-thirds of people who think they are gluten-intolerant really aren’t. Part of the problem is that there is a lot of really bad science out there on gluten intolerance. As one scientific editorial notes drily, much of the literature “suffers from significant methodological flaws,” such as very small numbers and no control groups. Some websites claim that one’s depression, arthritis, social phobias, or epilepsy, among other problems, might be caused by gluten intolerance.
Until the science gets sorted out, perhaps the best course for physicians is to suspect celiac disease and diagnose or exclude it correctly. They should also help patients sort through the conflicting data on wheat allergy and gluten intolerance. At the same time, patients convinced they have gluten intolerance might do well to also accept that their self-diagnosis may be wrong. In the end, it seems, medical uncertainly can best be approached by a little open-mindedness and humility from us all.