Gluten: Friend or Foe?
The first time I made short-crust pastry as a high school student, it was a complete disaster. I thought I had followed the teacher’s instructions properly. Instead, when it was time to line my pie dish, I found myself wrestling with a mound of pastry with the consistency of a forgotten piece of pre-loved chewing gum. What had gone wrong? The answer: my teenage enthusiasm had caused me to overwork the dough. And overworked dough made of wheat flour produces gluten. A clear case of gluten as the enemy.
Fast forward a decade or so, and we are in the midst of a gluten-free trend. This is good news for people with celiac disease, who must follow a life-long gluten-free diet and now have a much larger array of foods to choose from that are safe for them to eat. Others may be interested in eating gluten-free for purported health reasons or to avoid gluten intolerance. However, the term “gluten” used in this sense is actually a misnomer. Some bloggers have attempted, not terribly successfully, to explain the essential information about gluten and how it is related to health. Now it is time for TalkingNutrition to set the record straight.
Gluten is actually considered a “composite protein” – it is made out of two proteins, a prolamin and a glutenin, which form gluten when they are mixed together with water. Gluten contains about 50% prolamins according to the Codex Alimentarius (the New Zealand Baking Industry Research Trust provides a simple explanation here, and the Cooking Science Guy has a more scientific overview including some scanning electron microscope photos of gluten in wheat flour here). In my pastry catastrophe, energetic mixing had caused gluten to form. However in bread, gluten as formed by kneading the dough is desirable as it gives bread its chewy texture and allows it to rise. While gluten is the enemy of melt-in-the-mouth pastry-makers, it is bread baker’s friend.
The prolamins in wheat, barley and rye are gliadin, hordein and secalin, respectively, which is important to know, as they are responsible for the toxic reaction in celiac patients. As Thompson explains, people with celiac disease experience an auto-immune reaction in the lining of their small intestine after it is exposed to certain amino acid sequences in gliadin, hordein and secalin. Tests used to measure levels of “gluten” in foods actually target these specific proteins and not gluten itself. This is understandable, as people with celiac disease will react to the prolamins in cereal products, and the amount of gluten that has been formed by mixing is irrelevant.
It is clear that whether “gluten” is undesirable depends on your own personal situation. Currently, the only known treatment for celiac disease is a life-long gluten-free (and thus prolamin-free) diet. The exact cause of “gluten” intolerance is unknown however it can be diagnosed after celiac disease is ruled out, symptoms resolve after a gluten-free diet is introduced, and a gluten challenge produces a return of the undesirable symptoms, according to Tonutti and Bizzaro. A condition that may also resolve on a gluten-free diet is wheat-protein allergy. Allergy to the four classes of protein found in wheat – gliadin, glutenin, albumin and globulin – is possible and as gluten-free diets generally do not contain wheat, it may be helpful for wheat allergy. For these people, gluten is the enemy.
The gluten-free diet is not without its problems. First of all, the choice of gluten-free products has expanded but does not offer as much consumer choice as a standard diet. Gluten-free products attract a price premium: Stevens and Rashid report a 242% price premium compared to conventional products, with a variation of 5% to 1000% higher. People who must avoid products containing gluten have to take extra precautions at social occasions that many of us take for granted such as enjoying food at parties and eating out at a restaurants with friends. The gluten-free diet may also place people at nutritional risk: in the long-term, intakes of fiber, folate, niacin and riboflavin may be limiting when people avoid gluten (Saturni et al.). Foods that contain gluten make an important contribution to micro- and macro-nutrient intakes, and can be considered a friend to many.
Except when making pastry.
Cynthia Sass. May 25, 2014. Time. 5 Things You Need to Know About Gluten. http://time.com/109157/5-things-you-need-to-know-about-gluten/
Codex Alimentarius. Codex Committee on Nutrition and Foods for Special Dietary Uses. CODEX STAN 118-1981. Standard for Foods for Special Dietary Use for Persons Intolerant to Gluten. 2008. http://www.codexalimentarius.org/download/standards/291/cxs_118e.pdf
Food Safety Authority of Ireland. Gluten-Free Foods. 2008. www.fsai.ie/WorkArea/DownloadAsset.aspx?id=1214
Mark Lang. February 20, 2014. New York Times. Gluten-Free is a Consumer-Driven Trend. http://www.nytimes.com/roomfordebate/2014/02/20/is-avoiding-gluten-a-risky-fad-or-a-healthy-diet/gluten-free-is-a-consumer-driven-trend
Stevens L, Rashid M. Gluten-free and regular foods: a cost comparison. Can J Diet Pract Res. 2008 Fall;69(3):147-50. http://www.ncbi.nlm.nih.gov/pubmed/18783640
Saturni L, Ferretti G, Bacchetti T. The gluten-free diet: safety and nutritional quality. Nutrients. 2010 Jan;2(1):16-34. doi: 10.3390/nu20100016. Epub 2010 Jan 14. http://www.ncbi.nlm.nih.gov/pubmed/22253989
Thompson T. Wheat starch, gliadin, and the gluten-free diet. J Am Diet Assoc. 2001 Dec;101(12):1456-9. http://www.ncbi.nlm.nih.gov/pubmed/11762742
Tonutti E, Bizzaro N. Diagnosis and classification of celiac disease and gluten sensitivity. Autoimmun Rev. 2014 Apr-May;13(4-5):472-6. doi: 10.1016/j.autrev.2014.01.043. Epub 2014 Jan 15. http://dx.doi.org/10.1016/j.autrev.2014.01.043