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SummaryBackgroundGrains are high in FODMAPs (Fermentable Oligo‐, Di‐, Monosaccharides And Polyols) and often considered as triggers of IBS symptoms.AimTo evaluate if rye bread low in FODMAPs would be better tolerated than regular rye bread in subjects with IBS.MethodsThe study was conducted as a randomised double blind controlled cross‐over study (n = 87). Participants were supplied with both regular rye bread and low‐FODMAP rye bread for 4 weeks. Symptoms were measured with a symptom severity scoring system (IBS‐SSS) and visual analogue scale (VAS) assessments of individual symptoms. Quality of life was monitored. Colonic fermentation was measured by the breath hydrogen test and dietary intake by food diaries.ResultsDietary fibre intake increased during both study periods compared to baseline. Many signs of IBS i.e. flatulence, abdominal pain, cramps and stomach rumbling were milder on the low‐FODMAP rye bread (P‐values: 0.04; 0.049; 0.01 and 0.001). The mean of VAS measurements was favourable towards LF bread [−3 (95% CI): −6 to −1, P = 0.02] but no differences were detected in IBS‐SSS or quality of life. The AUC of breath hydrogen values was significantly lower during the low‐FODMAP bread period (median 52.9 vs. 72.6; P = 0.01).ConclusionsLow‐FODMAP rye bread helps IBS patients to control their symptoms and reduces gastrointestinal gas accumulation. However, replacing regular rye bread by low‐FODMAP bread without concomitant broader dietary changes does not improve quality of life or IBS‐SSS. Nonetheless, inclusion of low‐FODMAP rye bread in diet might be one way that IBS patients could increase their fibre intake.

A low FODMAP (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols) diet allows most irritable bowel syndrome (IBS) patients to manage their gastrointestinal symptoms by avoiding FODMAP-containing foods, such as onions, pulses, and products made from wheat or rye. The downside of a low FODMAP diet is the reduced intake of dietary fiber. Applying sourdoughs—with specific FODMAP-targeting metabolic properties—to wholegrain bread making can help to remarkably reduce the content of FODMAPs in bread without affecting the content of the slowly fermented and well-tolerated dietary fiber. In this review, we outline the metabolism of FODMAPs in conventional sourdoughs and outline concepts related to fructan and mannitol metabolism that allow development of low FODMAP sourdough bread. We also summarize clinical studies where low FODMAP but high fiber, rye sourdough bread was tested for its effects on gut fermentation and gastrointestinal symptoms with very promising results. The sourdough bread-making process offers a means to develop natural and fiber-rich low FODMAP bakery products for IBS patients and thereby help them to increase their dietary fiber intake.

Bakeries use sourdoughs to improve bread properties such as flavor and shelf life. The degradation of gluten proteins during fermentation may, however, crucially alter the gluten network formation. We observed changes that occurred in the HMW glutenins during wheat sourdough fermentations. As fermentation starters, we used either rye sourdough or pure cultures of lactobacilli and yeast. In addition, we incubated wheat flour (WF) in the presence of antibiotics under different pH conditions. The proteolytic activities of cereal and sourdough‐derived proteinases were studied with edestin and casein. During sourdough fermentations, most of the highly polymerized HMW glutenins degraded. A new area of alcohol‐soluble proteins (≈30.000 MW) appeared as a result of the proteolytic breakdown of gluten proteins. Very similar changes were observable as WF was incubated in the presence of antibiotics at pH 3.7. Cereal and sourdough‐derived proteinases hydrolyzed edestin at pH 3.5 but showed no activity at pH 5.5. An aspartic proteinase inhibitor (pepstatin A) arrested 88–100% of the activities of sourdough enzymes. According to these results, the most active proteinases in wheat sourdoughs were the cereal aspartic proteinases. Acidic conditions present in sourdoughs create an ideal environment for cereal aspartic proteinases to be active against gluten proteins.