Celiac and IBS: What is the Overlap?
A small but growing body of research examines the role of a low-FODMAP diet in patients with celiac disease (CD). CD is an immune-mediated disorder that affects roughly 1% of the population and requires a life-long gluten-free diet (GFD) [1]. Despite adherence to a GFD, an estimated 38% of CD patients continue to experience gastrointestinal (GI) distress [2]. Ongoing GI symptoms pose a significant burden and reduce quality of life [3].
Irritable bowel syndrome (IBS) is a functional GI disorder with an estimated prevalence of 4-11% [4]. The clinical picture of persistent CD overlaps with that of IBS. Common symptoms include diarrhea, abdominal pain, bloating, gas, constipation, and fatigue. An estimated 20% of CD patients fulfill the criteria for an IBS diagnosis [5]. Common treatment for IBS includes a low- fermentable oligo-, di-, monosaccharides and polyols (FODMAP) diet, which reduces symptoms in 50% to 80% of patients [6]. Though a formal cut-off has not been defined, reduction of FODMAPs to <12g per day is generally considered “low” [7].
Low-grade inflammation is common in both CD and IBS and symptoms of the two conditions share common pathologies [5]. These include dysregulation of the brain-gut axis, mucosal inflammation, visceral hypersensitivity, dysmotility, disease or infection and altered gut microbiota [8]. For patients with CD in remission on a GFD who continue to experience GI distress, a diagnosis of IBS may be warranted. Before doing so, a duodenal biopsy may be required to rule out potential alternative causes of symptoms, such as microscopic colitis, exocrine pancreatic insufficiency, bile acid malabsorption and villous atrophy [8].
The Gluten-Free Low-FODMAP Diet for Celiac Disease
For CD patients in remission who also meet criteria for IBS, a low-FODMAP diet can be used in conjunction with a GFD. A randomized control trial (RCT) of a gluten-free LFD in patients with CD showed improvements in abdominal pain, fecal consistency and overall well-being after 21-days [9]. A second RCT observed a similar improvement in GI symptoms among CD patients following a gluten-free LFD, along with improvements in celiac-specific health measures [3]. Similarly, a pilot study demonstrated the effectiveness of a gluten-free LFD in reducing abdominal pain, distension, and flatulence among adult CD patients with biopsy-confirmed remission [8]. The longest study to evaluate the impact of a gluten-free LFD saw improvements at 1 month and 3 months, though it should be noted that by the 3-month mark patients on a LFD should begin the reintroduction phase of the LFD [10].
Assessing Nutritional Adequacy
Low carbohydrate and fiber intake has long been a concern with the LFD and high intake of processed foods has been observed among those on a GFD. Gluten-free foods are often higher in fat, sugar and energy and lower in nutrients and fiber than their gluten-containing counterparts [11]. Combining these two restrictive diets may have harmful nutritional consequences when not implemented properly.
A recent RCT compared the nutritional adequacy of a GFD with a gluten-free LFD and found no difference in the overall nutritional quality of each, though both groups did not meet their daily energy requirements [12]. Participants on both diets also did not meet daily recommendations for iron, calcium, vitamin D, sodium, and folate. Those on a gluten-free LFD consumed more fruits and animal protein and lower amounts of legumes and grains than those on the GFD [12]. These findings point to the importance of working with a Registered Dietitian to customize a diet that is as liberal as possible, without triggering symptoms, regardless of the diet type.
Prior research on the LFD showed a LFD had no impact on relative abundance of gut bacteria associated with colonic health [13]. A probiotic supplement may be considered to prevent changes in the gut microbiota, especially during the first phase of the LFD. While reduced prebiotic intake has also been a concern for patients on a LFD, research has shown that a reduction in dietary prebiotics has not lead to the expansion of harmful bacteria as originally feared [13]. It’s important to note that almost all research to date examines the impact of the first phase of a LFD, where all FODMAPs are reduced, and not the third phase of the LFD, where FODMAPs that do not trigger symptoms are reintroduced into the diet. Still, low-fiber and vitamin and mineral intake should remain a concern when eliminating both gluten and reducing FODMAPs. Long-term research on a gluten-free LFD is undoubtedly warranted.
The restrictive nature of a gluten-free LFD also poses psychosocial risks. This strict dietary regimen can impact emotional wellbeing and social relationships and may carry a high financial burden. For CD patients, this can result in even lower food variability and more challenges to eating outside of the home. A gluten-free LFD should not be recommended to patients at risk for an eating disorder or nutritional inadequacy.
In Practice: The Gluten-free Low-FODMAP Diet
While a LFD is not inherently gluten-free it does restrict wheat, rye and barley, all of which are grains that also contain gluten. Many patients are unfamiliar with the difference between gluten (the protein) and fructan (the FODMAP found in many plant products). When it comes time for patients on a LFD to challenge fructan, there are plenty of gluten-free fructan-containing foods for them to trial. These include onion, garlic, grapefruit, pomegranate, chai or chamomile tea, dried figs and much more. Encourage CD patients who do wish to trial a LFD towards high-fiber, high-protein grains like amaranth, buckwheat, quinoa, rice, millet and certified gluten-free oats. Many of Schär’s gluten-free sourdough breads and crackers are certified low-FODMAP by Monash University and contain ancient grains, making them a delicious, nutritious source of fiber.
References
- Ludvigsson JF, Bai JC, Biagi F, et al. Diagnosis and management of adult coeliac disease: guidelines from the British Society of Gastroenterology. Gut 2014;63:1210–1228.
- Sainsbury A, Sanders DS, Ford AC. Prevalence of irritable bowel syndrome-type symptoms in patients with celiac disease: a meta-analysis. Clin Gastroenterol Hepatol 2013;11:359–365.