SAN FRANCISCO (FRONTLINE MEDICAL NEWS) – Elimination diet crazes have been around for centuries, and one of today’s biggest targets is gluten, contributing to an industry of gluten-free products with revenue in the billions of dollars.

But does taking gluten off your child’s plate actually improve their health? It will if they have a condition in which gluten actually causes symptoms, explained Michelle M. Pietzak, MD , a pediatrician at the University of Southern California, Los Angeles.

But it’s not always the gluten, she said at the annual meeting of the American Academy of Pediatrics.

Gluten is a mixture of proteins found in wheat, rye, barley, oats, corn, and rice that gives food its elasticity and helps dough rise. Only the gluten in wheat, rye, and barley causes gluten-related symptoms, but it is found in a variety of derivative products, such as spelt, kamut, triticale, couscous, bulgar, faro, matzo flour, and other grains as well. Oats are also considered cross-contaminated with gluten because they are milled with wheat, and other foods containing gluten may be difficult to identify due to food labeling and preparation practices in the United States.

For those with celiac disease, wheat allergy, irritable bowel syndrome (IBS), or nonceliac gluten sensitivity or intolerance, a gluten-free diet can reduce or eliminate the symptoms causing problems. For others, however, the symptoms likely come from somewhere besides gluten or may be a nocebo effect, where a patient who expects negative symptoms becomes more likely to have them.

Lactose intolerance is one example that can cause symptoms similar to those that respond to restricting gluten. Another is sensitivity to fructans, a wheat carbohydrate and one of the fermentable oligo-di-monosaccharides and polyols (FODMAPs) that can improve IBS when restricted. Imbalance in a person’s gut bacteria, called dysbiosis, also may cause similar symptoms and results from excess yeast, parasites, or an overgrowth of bad bacteria in the absence of beneficial ones.

Understanding celiac disease

This immune-mediated disease causes primarily gastrointestinal symptoms when someone ingests proteins called prolamines, which those with celiac disease are genetically predisposed to have difficulty digesting. Common symptoms include diarrhea, nausea, vomiting, abdominal pain, constipation, appetite changes, and, in unusual cases, excess fat in the feces (steatorrhea).

But celiac disease also may contribute to a short stature, osteoporosis, dermatitis herpetiformis, delayed onset of puberty, infertility, anemia (from iron and/or folic acid deficits), epilepsy, and behavioral changes. Although those with celiac disease are at a higher risk for arthritis, osteoporosis, osteopenia, osteomalacia, and rickets, a gluten-free diet can improve children’s low bone mineral density.

Screening for celiac disease includes testing for antigliadin (AGA) IgG and IgA, antiendomysial IgA, anti-tissue transglutaminase (tTG) IgA, total serum IgA, and genetic testing related to HLA-DQ2 and HLA-DQ8 genes.

Wheat allergy

A wheat allergy, among the eight most common food allergies, involves an IgE-mediated reaction to water- and salt-insoluble gliadins, especially omega-5 gliadin, which can cause anaphylaxis in a wheat-allergic person who exercises after ingesting wheat. Symptoms of wheat allergy include hives; swelling, itching or irritation of the mouth, throat, eyes, and nose; difficulty breathing; and cramps, nausea, vomiting, and diarrhea. Wheat allergy most commonly occurs in infants or toddlers, and typically co-occurs with other food allergies, but children usually outgrow the allergy by ages 3-5 years.

Nonceliac gluten sensitivity or intolerance

Physicians only should consider gluten insensitivity or intolerance after ruling out celiac disease and wheat allergy. Less understood and more controversial, gluten sensitivity or intolerance may be an immune-mediated condition – or instead an intestinal malfunction. Some patients may simply have an intolerance to high fiber foods in general. Patients with this insensitivity or intolerance will have a normal intestinal biopsy, but AGA IgG and/or IgA testing and genetic HLA-DQ2 testing may be positive. The clinical diagnosis is ultimately one of exclusion determined when a gluten-free diet alleviates symptoms.

Although gas, diarrhea, weight loss, and abdominal pain are the most common symptoms, other transient symptoms may include dyspepsia, nausea, vomiting, bloating, constipation, intestinal rumbling, joint or bone pain, muscle cramps or pain, fatigue, numbness, cramps, headaches, rashes, tongue inflammation, anemia, leg numbness, osteoporosis, or unexplained anemia.

Another potential effect of gluten sensitivity is dermatitis herpetiformis, a skin inflammation involving blisters, hives, or other types of erythematous or urticarial papules, usually symmetrically distributed, with severe itching. Although 90% of individuals with dermatitis herpetiformis lack any gastrointestinal symptoms, about 75% have villous atrophy, Dr. Pietzak said.

Even less understood are neurologic symptoms of gluten sensitivity and their potential mechanisms. Reported neurologic symptoms of gluten sensitivity include ataxia, peripheral neuropathy, depression, schizophrenia, epilepsy, and intracranial calcifications.

Irritable bowel syndrome

The similarity of symptoms between IBS and celiac disease has meant many with celiac disease were misdiagnosed with IBS, particularly women, Dr. Pietzak said. To confuse matters more, restricting gluten has shown improvement in IBS symptoms for some patients: in one study, 60% of those with diarrhea returned to having normal stools after 6 months of a gluten-free diet. Again, AGA IgG and tTG IgG testing was more likely to be positive among these patients. IBS and celiac disease can co-occur in patients, but it’s necessary to rule out celiac disease before diagnosing a patient with IBS.

What about autism?

One complementary and alternative medicine treatment promoted by some for autism is a gluten-free, casein-free diet, yet little evidence supports a link between autism spectrum disorders and gluten or casein. A pair of Cochrane Reviews in 2004 and 2008 found only three randomized controlled trials, with 35 participants combined, looking at this issue.

One found “reduced autistic traits of social isolation and bizarre behavior” at 12 months old following a gluten-free, casein-free diet, but the two others found no differences in physiologic functioning, behavior problems, autistic symptoms, or cognitive, motor, or communication/language skills. Such a diet only should be recommended, then, following diagnosis of an intolerance or allergy to a particular food. Although gluten-free, casein-free diets are typically well tolerated, they are costly and more difficult to prepare.

“A child with autism is already restricted in lifestyle by his or her disorder,” Dr. Pietzak said, so further lifestyle restrictions with diet may harm the child’s quality of life. If parents do choose to put their autistic child on a casein-free diet, they may need to supplement with calcium and vitamin D.

Importance of differential diagnosis

It’s important to know the difference between celiac disease and other conditions because patients may face different risks even if their treatment is similar. Those with celiac disease, for example, have a greater risk of nutritional deficiencies leading to conditions such as iron-deficiency anemia and osteoporosis, and are more likely to develop gastrointestinal cancers or other autoimmune conditions, such as thyroid disease, type 1 diabetes, joint diseases, and liver diseases.

Those with food allergies and intolerances do not share those increased risks, and their symptoms resolve without long-term organ damage when they remove the gluten or wheat from their diet. Further, only those with celiac disease must restrict all foods with gluten. Those with a wheat allergy may be able to eat rye, barley, and oats, for example, and restricting gluten may improve IBS symptoms for only a subset of patients.

Dr. Pietzak has consulted for Nestle Nutrition and is on the speaker’s bureau for Prometheus Labs.