Grain of truth: Celiac disease, gluten sensitivity and wheat allergy

Suddenly the gluten-free diet is fashionable; it was reported up to one third of population is doing or thinking about doing gluten-free diet, or at least cutting back the gluten intake. No wonder all the food manufacturing companies are pouring out gluten-free products, treating gluten like pest.  I never chased the fashion, but I better talk about this, lest people might suspect I do not keep up with the medicine.

bread made by Janice

Gluten is a protein made of glutenin and gliadin, forming a reticular matrix, trapping the carbon dioxide that comes from the yeast fermentation; thus the dough rises.  When Janice made the delectable and chewy ciabatta breads (see photos) and Miao-Chi and Xiao always let me take some specialty breads home when I visited the Bean Town; I gave thanks to Janice, Miao-Chi and Xiao and gluten, which gave us the texture we love.  Glutens are found in wheat, barley and rye.

Celiac disease is an autoimmune disease in that our immune system treats the gluten (especially its component gliadin) as a hostile invader and attacks it, thus one of the serology test is the IgG-deamidated gliadin peptide antibody.  It only happens in susceptible individuals that bear certain gene such as HLA-DQ2 haplotype that is expressed in 90% of patients with celiac disease, whereas it is expressed in one third of the general population.  Imagine autoimmune response is like using the small intestines as the battle ground and the end result is the damage to the intestine mucosa (villi).

bread made by Janice

One with celiac disease usually presents with chronic diarrhea, abdominal pain, bloating, nutritional deficiency, osteoporosis/osteopenia, or may have abnormal liver function, and rarely a skin rash called dermatitis herpetiformisis.  It is estimated that up to 1% of population may have celiac disease; it is obviously under diagnosed; a doctor needs to keep vigilant; when in doubt, check it out.  If suspicion is raised, you doctor will first order some blood tests including liver function test.

The serology test of first choice is IgA anti-tissue transglutaminase antibody; in case of IgA deficiency, the alternative tests would be IgG anti-tissue transglutaminase antibody and IgG-deamidated gliadin peptide antibody. IgA antiendomysial antibody is another choice.

If these antibody tests turn out to be positive, then do an endoscopy with small bowel (duodenum) biopsy to obtain the most definite diagnosis.  The treatment is to remove the culprit—gluten—from the diet.

Celiac disease was first described around Jesus time by a Greek doctor; in fact “celiac” comes from Greek, koiliaki, which means “abdominal”.  Wheat was first implicated in 1944; during a Dutch famine, a doctor observed celiac disease almost disappeared when wheat was no longer available.

Then what is the “gluten sensitivity” or “gluten intolerance”? It spreads like a wild fire.  Those with gluten sensitivity present with similar, albeit milder, symptoms of celiac disease.  It is not an autoimmune disease, thus the serology tests are negative, as is HLA-DQ2 haplotype. The small intestine biopsy would be normal, if done.

Many people claim their symptoms improve following a gluten-free diet, at present the medical professional is hesitated to say it is a placebo effect.  However, the prevalence, pathophysiology and natural history remain elusive.  Gluten sensitivity is not a celiac disease; that much we’re sure, but if there were any relationship, nobody knows.  Following strict gluten-free diet unnecessarily may not be in the best interest of one’s health, it may deprive you of the fiber and many nutrients, not to mention the indulgence.

If celiac disease is under diagnosed, the gluten sensitivity is definitely over diagnosed and many of them self-diagnosed.  The fact many celebrities proclaimed they are on gluten-free diet helped adding the fuel to the fire.  This is not to say that gluten sensitivity is not considered a disease entity, though.

Wheat allergy is also an immune system disease, but it involves IgE, an innate immunity, whereas celiac disease involves IgA and IgG, an adaptive immunity. Gluten-free diet also benefits one with wheat allergy, but they can consume barley and rye with no problem.