Spotlight on gluten avoidance
An industry-funded trial of patients with self-reported gluten sensitivity found that symptoms were tied to the expectation of gluten more than actual consumption, while a study of celiac disease patients found that their symptoms often persisted after elimination of gluten.
Two recent studies looked at the effects of gluten consumption or avoidance on symptoms.
The first study, published by The Lancet Gastroenterology & Hepatology on Nov. 28, looked at nonceliac gluten sensitivity (NCGS). The industry-funded trial included 84 patients in England and the Netherlands with self-reported NCGS (defined as GI symptoms within eight hours of gluten consumption). All followed a gluten-free or gluten-restricted diet for at least a week before being randomized to one of four groups: to expect gluten and actually get it (E+G+), to expect it and not get it (E+G−), to not expect it and get it (E−G+), or to not expect it and not get it (E−G−). The intervention was provided as two slices of oat bread at breakfast and again at lunch. The study was funded by a number of wheat and food production organizations and companies.
The primary outcome was overall gastrointestinal symptom score on the Visual Analogue Scale, assessed in 83 participants (median age, 27 years; 86% women). The mean score was significantly higher when patients were expecting gluten than when they got it without expecting it (16.6 mm in E+G+ vs. 6.9 mm in E−G+; difference, 9.6 mm [95% CI, 3.0 to 16.2 mm], P=0.0010). Patients who were expecting gluten and didn't get it had similar scores to those who weren't expecting it, whether or not they actually received it. (11.7 mm E+G− vs. 6.9 mm in E−G+ and 7.4 mm in E−G−). Adverse events were reported by two participants in the E+G− group (itching jaw, feeling lightheaded and stomach rumbling) and one in the E−G+ group (vomiting). “These findings add weight to our hypothesis that a nocebo effect is involved in symptom occurrence in NCGS,” said the study authors, who called for further research into the role of gut-brain interaction in NCGS.
“This study provides further evidence to support the idea that NCGS is not a distinct clinical entity but an umbrella term encompassing a heterogeneous group of patients, with a substantial symptom overlap with coeliac disease, [irritable bowel syndrome], functional dyspepsia, and food allergy or sensitivity,” said an accompanying editorial. The editorialists recommended comprehensive and individualized approaches to diagnosis of such patients “to avoid the potential harms of an unnecessary long-term gluten-free diet.”
The other study, published by the Journal of Clinical Gastroenterology on Nov. 27, focused on patients with biopsy-proven celiac disease who were on a gluten-free diet. It involved a retrospective review of 212 charts of patients referred to a tertiary center (69% women; mean age at diagnosis, 43 years). During follow-up, more than half of patients remained symptomatic (48.9% at six months, 58.3% at a year, 63.1% at five years). Many still had the same symptoms that had prompted diagnosis. The only predictors for remaining symptomatic were female sex and younger age at diagnosis; ongoing abnormal serology and small-bowel normalization were not predictive.
There are a number of possible explanations for the continued symptoms, including celiac disease being an incidental finding with another disease causing patients' symptoms, slow response to a gluten-free diet, or minute levels of gluten exposure triggering symptoms, according to the study authors. “These findings stress the importance of long-term care in celiac disease,” they said. “The frequency of persistent or even new symptoms may not be appreciated by primary care providers. It is critical to identify those who remain symptomatic so that the appropriate investigation can be undertaken and to consider evaluating for intestinal healing even in the absence of symptoms.”