The Molecular Basis for Oat Intolerance in Patients with Celiac Disease

BACKGROUND: Celiac disease is a small intestinal inflammatory disorder characterized by malabsorption, nutrient deficiency, and a range of clinical manifestations. It is caused by an inappropriate immune response to dietary gluten and is treated with a gluten-free diet. Recent feeding studies have indicated oats to be safe for celiac disease patients, and oats are now often included in the celiac disease diet. This study aimed to investigate whether oat intolerance exists in celiac disease and to characterize the cells and processes underlying this intolerance. METHODS AND FINDINGS: We selected for study nine adults with celiac disease who had a history of oats exposure. Four of the patients had clinical symptoms on an oats-containing diet, and three of these four patients had intestinal inflammation typical of celiac disease at the time of oats exposure. We established oats-avenin-specific and -reactive intestinal T-cell lines from these three patients, as well as from two other patients who appeared to tolerate oats. The avenin-reactive T-cell lines recognized avenin peptides in the context of HLA-DQ2. These peptides have sequences rich in proline and glutamine residues closely resembling wheat gluten epitopes. Deamidation (glutamine→glutamic acid conversion) by tissue transglutaminase was involved in the avenin epitope formation. CONCLUSIONS: We conclude that some celiac disease patients have avenin-reactive mucosal T-cells that can cause mucosal inflammation. Oat intolerance may be a reason for villous atrophy and inflammation in patients with celiac disease who are eating oats but otherwise are adhering to a strict gluten-free diet. Clinical follow-up of celiac disease patients eating oats is advisable

Safety of Adding Oats to a Gluten-free Diet for Patients with Celiac Disease: Systematic Review and Meta-analysis of Clinical and Observational Studies

Background & Aims: Patients with celiac disease should maintain a gluten-free diet (GFD), excluding wheat, rye, and barley. Oats might increase the nutritional value of a GFD, but their inclusion is controversial. We performed a systematic review and meta-analysis to evaluate the safety of oats as part of a GFD in patients with celiac disease. Methods: We searched the Cochrane Central Register of Controlled Trials, MEDLINE, and EMBASE databases for clinical trials and observational studies of the effects of including oats in GFD of patients with celiac disease. The studies reported patients’ symptoms, results from serology tests, and findings from histologic analyses. We used the GRADE approach to assess the quality of evidence. Results: We identified 433 studies; 28 were eligible for analysis. Of these, 6 were randomized and 2 were not randomized controlled trials comprising a total of 661 patients—the remaining studies were observational. All randomized controlled trials used pure/uncontaminated oats. Oat consumption for 12 months did not affect symptoms (standardized mean difference: reduction in symptom scores in patients who did and did not consume oats, −0.22; 95% CI, −0.56 to 0.13; P = .22), histologic scores (relative risk for histologic findings in patients who consumed oats, 0.24; 95% CI, 0.01–4.8; P = .35), intraepithelial lymphocyte counts (standardized mean difference, 0.21; 95% CI, reduction of 1.44 to increase in 1.86), or results from serologic tests. Subgroup analyses of adults vs children did not reveal differences. The overall quality of evidence was low. Conclusions: In a systematic review and meta-analysis, we found no evidence that addition of oats to a GFD affects symptoms, histology, immunity, or serologic features of patients with celiac disease. However, there were few studies for many endpoints, as well as limited geographic distribution and low quality of evidence. Rigorous double-blind, placebo-controlled, randomized controlled trials, using commonly available oats sourced from different regions, are needed

Oats in the gluten-free diet. With special reference to clinical, serological and nutritional effects, subjective experiences and the need for special oat products

Oats have for over 50 years been excluded from the gluten-free diet (GFD). The scientific basis for this recommendation is weak, and two studies performed during the 1990's stated that moderate amounts of oats were well tolerated in the GFD of adults with celiac disease (CD), followed for 3-12 months. The aims of the present investigation were to study the clinical, serological and nutritional effects of including large amounts of guaranteed not-contaminated oats, for a period of two years, in adult subjects with CD in remission. We were also interested in whether commercial oat products are suitable for subjects with CD, i.e. not contaminated with gluten. No adverse effects of a large intake of oats (median 93g/d) were seen in small bowel histology, serology nor in nutritional status in the 15 subjects who completed the 2-year study period. Anti-avenin antibodies were not induced after inclusion of oats. This has not been investigated in previous clinical studies. Beneficial effects were seen, as the intake of iron, fibre, zinc and thiamin increased when oats were included in the diet. The bioavailability of iron tended to decrease due to large amounts of phytate in oats but this seems not to have influenced the iron status of the participants. Temporary gastrointestinal symptoms, mainly flatulence and distension of the bowel, were observed, as were subjective improvement of the bowel function. Oats in the diet were appreciated by the subjects, who found that oats gave more variation, better taste and satiety. The analysis of the commercially oat products showed that contamination by wheat, rye and/or barley occur. The same picture was noted in products naturally gluten-free (NGF), analysed for comparison. In conclusion: adult subjects with CD in remission can include large amounts of not-contaminated oats in their daily GFD for an extended period of time without adverse effects. Beneficial effects were seen in nutrient quality of the diet and subjective experiences. However, only special oats and NGF products can be recommended in the GFD due to risk of contamination