ReviewThe low-FODMAP diet for irritable bowel syndrome: Lights and shadowsDieta con bajo contenido en FODMAP para el síndrome del intestino irritable: luces y sombras
Introduction
Irritable bowel syndrome (IBS) affects 10–20% of individuals worldwide.1 The condition is characterized by chronic abdominal pain associated with disordered defecation or a change in bowel habit.2 IBS has a considerable effect on quality of life and people with IBS spend more days in bed, miss more work days, have more consultations with their primary care physician than those without the condition, besides social functioning is even worse in IBS than in other chronic diseases such as diabetes.3 Furthermore, the chronic nature of IBS, its high prevalence and its associated comorbidities contribute to a considerable economic burden on health-care services.4, 5
The pathophysiology of IBS is complex and multifactorial, including altered gastrointestinal motility, increased gastrointestinal fermentation, abnormal gas transit, visceral hypersensitivity, brain – gut axis dysregulation, dysbiosis of the gut microbiota, genetic predisposition and psychosocial aspects.6 Treatment of IBS has historically been symptom-directed (e.g., bulking agents, antispasmodic agents) or centrally acting (e.g., antidepressants, cognitive–behavioral therapy), but the efficacy of these treatments is limited.
Many patients believe that their IBS symptoms are diet-related,7 but evidence supporting the effect of dietary intervention on IBS symptoms has been of limited quality. A controversial study on the efficacy of a tailored therapy for IBS, based on serum IgG levels to foods, definitely set off this line of thinking in 2004.8 The authors suggested a 3-month diet based on IgG results was significantly more effective for IBS symptoms than a sham diet, excluding the same number of foods, but not those to which they had antibodies. This study was much contested due to design and methodological flaws that questioned their conclusion, since the treatment group excluded significantly more different foods than the control group, particularly those foods which appear to exacerbate symptoms of IBS.9, 10 As such, differences between diets could largely be explained not by specific identification of food reactions by IgG testing, but rather by the gross differences between the two diets. This questionable study, however, proved dietary restriction was effective for IBS and paved way for a growing interest in dietary approaches for the management of IBS among both clinicians and patients.11
Section snippets
The FODMAP concept
In parallel with the rising incidence for gastrointestinal diseases (IBS, inflammatory bowel disease or celiac disease) over the past two decades, patterns of food intake and dietary behavior have dramatically changed worldwide. Fructose consumption has increased fourfold in children <10 years old and around 20% in general population. Caloric sweeteners are commonly used for beverages, intake of fast food (pizza, hamburgers, snacks, beverages) and wheat-containing foods (pasta, bread, cakes)
FODMAPs in the diet
The content of FODMAPs in the diet varies across geographical areas due to variable doses delivered in the diet, the most common being fructose and fructans.22 For instance, consumption of fructans/galacto-oligosaccharides (GOS) is higher in the Mediterranean countries due to increased bread and legume intake. High FODMAP food sources (where FODMAPs are problematic based on standard serving size) and suitable low FODMAP alternatives, according to food analysis conducted in Australian foods,23,
Pathophysiological rationale for low FODMAP diet
The rationale behind using low FODMAP diet is that a reduction of the detrimental gastrointestinal effects of non-absorbed carbohydrates, mainly increase in luminal water content and bacterial fermentation, will likely improve symptoms in IBS patients.21, 22 After FODMAP ingestion, increased delivery of water to the small intestine (measured by magnetic resonance imaging)34, 35 and the proximal colon (ileal effluent in ileostomates patients),19 due to their osmotic effects, have been
The efficacy of low FODMAP diet for irritable bowel syndrome
A number of clinical uncontrolled studies from Australia, New Zealand, Norway, United Kingdom, Denmark and Spain15, 46, 47, 48, 49, 50, 51 have consistently shown the efficacy of low FODMAP diet for IBS. Solid evidence supporting the efficacy of low FODMAP diet relies on five controlled trials, four of these being randomized controlled trials (RCT) (Table 2).20, 52, 53, 54, 55 The non-RCT compared low FODMAP diet to standard dietary advice for IBS, according to recommendations from The National
The efficacy of low FODMAP diet for non-celiac gluten sensitivity
Non-celiac gluten sensivity (NCGS) is an emerging disorder characterized by intestinal and extraintestinal symptoms related to the ingestion of gluten-containing food, in patients who are not affected by either celiac disease or wheat allergy. Due to the absence of reliable biomarkers, NCGS remains a diagnosis of exclusion of celiac disease and most patients are self-diagnosed and voluntarily start a gluten-free diet (GFD).57 A recent systematic review on NCGS has highlighted the lack of
Criticisms to low FODMAP diet
It is clear that IBS treatments are unsatisfactory in many cases. This is related to different aspects, ranging from the complex and incompletely understood pathophysiology of IBS to its enormous clinical heterogeneity. Moreover, some IBS medications (received with great expectations) had to be withdrawn from the market because of side effects.66 New promising drugs have been launched, and some others will be in the next future, but its final place in the treatment algorithm of IBS in the
Conflict of interest
The authors declare no conflict of interest.
Acknowledgements
We kindly appreciate the comments provided by Dr. Peter Gibson and his team from the Monash University in Australia.
References (76)
- et al.
Functional bowel disorders
Gastroenterology
(2006) - et al.
The burden of selected digestive diseases in the United States
Gastroenterology
(2002) - et al.
Importance of diet in irritable bowel syndrome
Gastroenterol Hepatol
(2014) - et al.
Fructose malabsorption and symptoms of irritable bowel syndrome: guidelines for effective dietary management
J Am Diet Assoc
(2006) - et al.
Dietary triggers of abdominal symptoms in patients with irritable bowel syndrome: randomized placebo-controlled evidence
Clin Gastroenterol Hepatol
(2008) - et al.
Reduction of dietary poorly absorbed short-chain carbohydrates (FODMAPs) improves abdominal symptoms in patients with inflammatory bowel disease – a pilot study
J Crohns Colitis
(2009) Inulin-type fructans: functional food ingredients
J Nutr
(2007)- et al.
Intestinal gas dynamics and tolerance in humans
Gastroenterology
(1998) - et al.
Normalization of lactulose breath testing correlates with symptom improvement in irritable bowel syndrome: a double-blind, randomized, placebo-controlled study
Am J Gastroenterol
(2003) - et al.
Reduction of dietary poorly absorbed short-chain carbohydrates (FODMAPs) improves abdominal symptoms in patients with inflammatory bowel disease-a pilot study
J Crohns Colitis
(2009)