No clear evidence exists to support the idea that celiac disease is increasing in prevalence because farmers are growing strains of wheat that contain more gluten. That's the conclusion of an article in the ACS' Journal of Agricultural and Food Chemistry.
Donald D. Kasarda cites evidence that the incidence of celiac disease increased during the second half of the 20th century. Some estimates indicate that the disease is 4 times more common today. Also known as gluten intolerance, celiac disease occurs when gluten, a protein in wheat, barley and rye, damages the lining of the small intestine, causing a variety of symptoms. Nobody knows why the disease is increasing. One leading explanation suggests that it results from wheat breeding that led to production of wheat varieties containing higher levels of gluten.
Kasarda's Perspective article examined the scientific evidence for that hypothesis and found that gluten levels in various varieties have changed little on average since the 1920s. Overall gluten consumption, however, has increased due to other factors. One involves increased consumption of a food additive termed "vital gluten," which has tripled since 1977. Vital gluten is a food additive made from wheat flour, and it is added to various food products to improve their characteristics, such as texture. Overall consumption of wheat flour also has increased, so that people in 2000 consumed 2.9 pounds more gluten annually than in 1970, nearly a 25 percent increase.
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More information: Article: "Can an Increase in Celiac Disease Be Attributed to an Increase in the Gluten Content of Wheat as a Consequence of Wheat Breeding? A Perspective," Journal of Agricultural and Food Chemistry.