Gluten sensitivity

The number of people who believe that they are sensitive to wheat gluten has reached almost epidemic proportions. “Gluten-related disorders” is the umbrella-term describing problems resulting from the ingestion of gluten-containing food.
The spectrum extends from the defined pathology of Coeliac Disease, to Gluten sensitivity which is free of demonstrable pathology and a prevalence estimated to be 6–10 times greater than coeliac disease. ¹
Wheat is the prime source of gluten. Wheat is an ancient crop. New wheat strains have been developed to meet increasing population demands. Shorter stems of growing wheat means less flattening in bad weather and wheat production yields have more than doubled. Even now further changes in wheat production are in prospect with proposed Genetically Modified wheats.
Modern wheat flour contains at least 12 per cent protein, largely gluten . Gluten is not a single molecular protein species but a mixture of proteins, the gliadins and the glutenins. A typical wheat variety may have as many as 40 different gliadins, whose molecular weights range between 28,000 to 55,000. The glutenins are macro-polymers with high molecular weight and low molecular weight subunits. Glutens form a continuous protein network with viscoelastic properties which are central to the process of dough and bread making. Glutamine-rich repetitive sequences, the core of the larger subunits are responsible for the dough creating elastic properties of wheat flour through their extensive arrays of interchain hydrogen and sulphide bonds. This enables the singular ability of gluten to form an open structure during yeast fermentation which is important in bread making, and which is fixed during baking to create a loaf. The addition of bread improvers alters the protein cross linkages. ² ³
A defining development, which changed baking practice throughout the world was the introduction of the Chorleywood bread process in 1961 by the British Baking Industries Research Association at Chorleywood UK. ⁴
The nutritional and digestion consequences of these wheat growing, genetic modification of wheat, milling and baking practices and their impact on gluten chemistry and properties are untested.
The digestion of most dietary proteins is by intestinal and villi petidases . Events in the intestine are seen as being totally a dismantling process. Gliadin is digested in he standard manner for proteins. However many of the gluten proteins are relatively resistant to intestinal digestion. This is due in part to the creation of Maillard type reaction products during baking and also as a result of the substantial proline content of the gluten. The post prandial gluten residues will be unusually enriched with glutamine, proline and glycine motifs comprising over 70% of the total gluten amino acid residues.
Many high molecular weight oligopeptides of gluten origin persist in the lumen of the small intestine and have the potential of themselves or after further modification to create peptides with distinct biological properties. By virtue of chemically active nitrogen and sulphydril side chains they have the potential to physically bind to each other or to larger proteins or mucoproteins or secreted pancreatic enzymes. ⁵ There may be novel chemicals produced through reactions between molecules enriched with nitrogen and sulphydril side chains.
Gluten peptides of various molecular weight pass into the colon where further digestion takes place. A resistant residue passes out in the faeces. ⁶
It is possible that there is further spontaneous or bacterial induced creation of biologically active constrained peptides in the intestine and colon. The original released peptides or subsequently created peptides might act locally in the intestine or be absorbed to act systemically.
The increase in individuals who experience ill effects from ingesting wheat flour or more specifically gluten may be the result of a number of factors. Are these people just seeking a health Nirvana? Or are they valetudinarians ? An easy, even facile dismissal. Alternatively there is the recognition that there have been considerable genetic changes in wheat and the processing of wheat flour to make bread. Wheat, flour , dough and bread have been carefully modified for the added efficiency of the baking process and the eating attraction of the resultant product. The structure, intestinal and colonic bacterial metabolism of wheat flour and gluten may well be different between traditional wheat and modern wheat. Rarely have the effect of these changes been studied in either the general or gluten sensitive population.
How might this be resolved? Ideally by controlled trials wherein standard modern wheat bread is eaten by gluten sensitive individuals, none coeliac individuals and compared with bread made from wheat , grown, milled and baked in a traditional manner.
Regardless however, it would be only be proper if when the wheat growers, millers or bakers make radical changes in wheat, bread production and gluten chemistry, then the nutritional consequences should be tested in an independent and published manner.
References

Kim H, Patel KG, Orosz E, Kothari N, Demyen MF, Pyrsopoulos N. Time trends in the prevalence of Celiac Disease and Gluten-Free Diet in the US population: Results from the National Health and Nutritional Examination Surveys 2009–2014. JAMA Intern Med 2016;176:5254
Anjum FM, MR Khan, A Din, M Saeed, I Pasha, MU Arshad. Wheat Gluten : High Molecular Weight Glutenin Subunits—Structure, Genetics and Relation to Dough Elasticity. Journal of Food Science 2007 ; 72 : R56–-R63.
Shewry PR, Halford N G, Belton PS, Tatham AS. The structure of gluten: an elastic protein from wheat grain. Phil.Trans. R. Soc. London B 2002; 357:133–143 .
Belderok B . Developments in bread-making processes. Plant Foods Hum Nutr 2000; 55 : 1–86.
Caminero A, Nistal E, Herran AR Perez-Andres J, Ferrero MA, Ayala LV et al . Differences in gluten metabolism among healthy volunteers, coeliac disease patients and first degree relatives. British Journal of Nutrition 2015; 114 :1157–1167
Caminero A, Nistal E, Arias L etc all. A gluten metabolism study in healthy
individuals shows the presence of faecal glutenasic activity. Eur J Nutr 2012; 51 :
293-299 .