Coeliac disease
Coeliac disease (non-IgE mediated gluten hypersensitivity) is mainly caused by the wheat storage protein gluten, which contains ethanol-soluble gliadin. Other cereals like rye, barley and oat contain gliadin homologous (secalin, hordein, and avenin, respectively). The disease occurs when people cannot tolerate gluten in more than small amounts. For this reason, “gluten-free” foods have been developed that only may contain a low level of gluten. The threshold level is set to 20 mg/kg at the moment. “Gluten-reduced foods” are allowed to contain 20 to 100 mg/kg of gluten.
Coeliac disease affects the small intestine and is triggered by ingestion of gluten. The gluten leads to an immunological reaction resulting in a flattening of the intestinal mucosa and thus impairing the absorption of nutrients, vitamins and minerals. Symptoms of coeliac disease are diarrhoea, weight loss, general weakness, anaemia, dementia, and osteoporosis.
The survey of gluten-free products is important because about 1 % of the total population suffer of this autoimmune disorder. A life-long gluten-free diet is the only ‘treatment’ for coeliac disease. Products containing wheat, rye, barley, and spelt must be avoided whereas oats are sometimes tolerated.
For more information about coeliac disease on the Web see:
http://www.glutenfree-diet.org/
http://www.gfoverflow.com/
Information on surveys of gluten-free Norwegian products:
- “Kartlegging av glutenfrie produkter på det norske marked i perioden 1999/2000“
- “Kartlegging av gliadin i glutenfrie produkter, havre og øl” (2002)“
Allergy to cereals
Allergy to cereals, most frequently to wheat, is not very common and occurs predominantly in children. Wheat (Triticum aestivum) grain proteins can be classified into water-soluble albumins, salt-soluble globulins, ethanol-soluble prolamins and acid- or alkali-soluble glutenins. A number of different allergens have been identified, e.g. the prolamins gliadin (Tri a 19), glutenin (Tri a 26), LTP (Tri a 14), and the pollen-related profilin (Tri a 12).
Barley (Hordeum sativum) grain allergens include LTP (Hor v 14) and hordein (Hor v 21). Rye (Secale cereale) grains contain among other allergens profilin (Sec c 12), secalin (Sec c 20), and oat (Avena sativa) grains profilin (Ave s 12) and avenin.
Wheat allergic patients may not tolerate gluten-free food, as they may react to other allergens than gluten, and/or to lower amounts of gluten. On the other hand, they may eat barley and rye.
Case report from the Norwegian Food Allergy Register
IgE mediated anaphylactic reaction to wheat in a patient with celiac disease (M. Løvik et al., 2011)
A 45-year old woman, who had been diagnosed with celiac disease at the age of 28, had an anaphylactic reaction to “gluten-free” bread bought from a local baker. Analysis of the patient’s serum showed high levels of specific IgE antibodies to wheat, rye, barley, and low levels of IgE antibodies to oat. The IgE antibodies did not bind significantly to the main gliadin fraction, but were targeted at allergens with a higher molecular mass.