Celiac.com 05/15/2017 - For all the talk of studies touting evidence for non-celiac gluten sensitivity, the actual data don't stack up very well, according to an recent assessment by two researchers, whose results appear in Clinical Gastroenterology and Hepatology.
For their study, the pair analyzed data from 10 separate double-blind, placebo-controlled, gluten-challenge trials on a total of 1312 adults. The available studies varied significantly in many ways. The duration of the gluten challenge, for example, varied from 1 day to 6 weeks. The daily doses for those gluten challenges varied from 2 grams to 52 grams, with 3 studies administering 8 grams or less each day. The composition of the gluten-free placebo also varied considerably between tests; including variation by gluten-free product type, and levels of xylose, whey protein, rice, or corn starch containing fermentable carbohydrates.
Most of the studies did find gluten challenge to significantly increase symptom scores compared with placebo. However, out of 231 NCGS patients, only 38 patients (16%) showed gluten-specific symptoms. Moreover, nearly half (40%) of these patients showed similar or increased symptoms in response to placebo; something researchers term a 'nocebo' effect. That leaves just 6 or 7 patients out of 231 showing gluten-specific symptoms.
The researchers also point to heterogeneity and to potential methodology flaws in gluten challenge studies. They also present powerful questions about gluten as the trigger for symptoms in most patients with presumptive NCGS. Lastly, they highlight the importance of the nocebo effect in these types of studies.
These results certainly invite more careful, rigorous studies on the matter, and challenge researchers to provide solid data from well-crafted double-blind placebo controlled studies.
Basically, what little evidence we thought we had to support the existence of non-celiac gluten sensitivity has been shown to be thin at best. Until solid evidence arrives, the status of non-celiac gluten sensitivity will remain open to question and doubt by both researchers and potential sufferers.
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