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Saturday, March 12, 2011

When Wheat is to Blame

We’ve heard reports accusing the pharmaceutical industry of manufacturing and promoting diseases in order to boost drug sales, so called “disease mongering.” Could it be that the health food industry is doing the same?  More and more of my patients and peers are going gluten-free.  Does this reflect the successful marketing of this food niche? Or, is it based on a growing recognition of real disease?

Wheat can causes health problems in two main ways—food allergies and genetically-based Celiac Disease.  The prevalence of Celiac Disease within the American population is approximately 1 in 100, making it, in fact, a common disorder.  Ninety five percent of afflicted individuals have the genetic profile, HLA-DQ2 or HLA-DQ8.  Typically 10% of first degree relatives are affected. This “auto-immune” disease is characterized by a T-cell mediated immune response to gluten, which results in inflammation in the duodenum and jejunum of the small intestine, causing destruction of the normal intestinal lining and diminishing one’s ability to absorb nutrients, such as vitamin D, calcium, and iron.  The clinical manifestations include diarrhea, abdominal pain and frequently weight loss. There also can be neurologic manifestations (cerebellar ataxia and peripheral neuropathy) and a blistering skin condition called dermatitis herpetiformis.  Celiac disease may be asymptomatic or minimally symptomatic for years.  Those left untreated are at higher risk for osteoporosis, lymphoma and adenocarcinoma of the small bowel.   Those afflicted are also more likely to have other autoimmune conditions, such as autoimmune thyroid disease and type I diabetes. The diagnosis of Celiac Disease can be made by screening a patient for particular antibodies in the blood—the endomysial antibody and the tissue transglutaminase antibody, which are highly sensitive and specific for Celiac Disease.   IGG and IGA antibodies should be measured.  In the past antibodies to gliadin were used as a diagnostic, however their low specificity (high false positive rate) has been recognized--approximately 10% of non-afflicted people have detectable anti-glaidin antibodies.  The diagnosis of Celiac Disease is confirmed by upper endoscopy and small bowel biopsy, which shows the characteristic findings of flat crypts and lymphocytic infiltration of the intestinal epithelium. Treatment is fairly straightforward with the elimination of gluten in one’s diet.  Success with treatment can be monitored through repeating the diagnostic antibody panel.  Antibodies typically normalize within 6 to 9 months of instituting a gluten-free diet, with elimination of wheat, barley and rye, and possibly also oats, which may be cross-contaminated with gluten containing cereals.  

Recently I diagnosed a patient after a routine physical, which uncovered unexplained severe iron deficiency (in the absence of anemia).  On further questioning the patient was also having trouble with episodic diarrhea and abdominal cramping—though this had not been a major complaint at the time of his physical.

In contrast to Celiac Disease, wheat allergy refers to an immune mediated reaction characterized by increased levels of serum IgE to wheat antigens that results in clinical symptoms of allergy affecting the skin, gastrointestinal tract or respiratory tract.  Diarrhea, abdominal pain, worsening of atopic dermatitis (an allergic skin rash), and asthma are common clinical manifestations.  In children there are six foods implicated in the vast majority (over 80%) of food allergy—peanuts, tree nuts, milk, eggs, soy and wheat.  Estimates of the prevalence of wheat allergy in the pediatric and adult population are difficult to determine but fall into the range of .5 to 3 % depending on what criteria are used for diagnosis.  Many adults who have positive serum levels of wheat antibody detectable on allergy testing report no clinical manifestations of allergy.  In contrast, many children whose parents report sensitivity to wheat products have no objective evidence of the allergy on either skin prick testing or serologies.  While clinical symptoms of food allergy are fairly prevalent in the pediatric population, most kids tend to outgrow their allergies between ages 3 and 5.   In general, the most accurate way to diagnose a suspected food allergy is through oral challenge testing performed in conjunction with serum or skin testing demonstrating an immune response.

Wheat is also a rare cause of a more severe type of allergy known as Wheat Dependent Exercise Induced Anaphylaxis (WDEIA), which manifests as anaphylaxis with exercise.  Anaphylaxis is when an allergy causes massive histamine release, resulting in chest tightness, shortness of breath and collapse of the circulatory system with a dropping of blood pressure—it is life threatening.  Other rare manifestations of wheat allergy are “Baker’s Asthma,” bronchial constriction triggered by the inhalation of raw wheat, and contact urticaria (hives) cause by use of topical wheat products in cosmetics.

Food is such an emotional topic for people.  It’s interesting to me to see how many are eager to embrace food as the cause for, or the remedy of their ills.  However, whether it’s pharma or the health food industry, one must be equally skeptical.  Take the recent Federal Trade Commission complaint against POM Wonderful pomegranate juice, which accused the company of false advertising.  It appears that in the case of the gluten-free market there is good reason for these products to be made available to those who truly need them. But, before you jump on the bandwagon, make sure that the evidence to blame your symptoms on wheat is solid.

For further information on Celiac Disease, the following are useful links:

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