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Low FODMAP Diet Clinical Evidence

The efficacy of a Low FODMAP Diet is supported by more than 30 clinical studies. A growing body of clinical research is bringing to the forefront new ideas about how to diagnose, understand, treat, and even alleviate the symptoms associated with Irritable Bowel Syndrome. In addition, translational research, such as that carried out by the Gastroenterology Research team at Monash University in Australia, is applying data from the lab to community interventions. Some of the most significant published works in this area, with emphasis on the Low FODMAP Diet, are summarized below. Links to journal abstracts follows.

1. Food Choices Can Impact Symptoms of Irritable Bowel Syndrome

Dr. Peter Gibson and Dr. Susan Shepherd prepared this review (2012) of the research on dietary interventions for the treatment of Irritable Bowel Syndrome. They summarized that indeed, limiting those foods in the diet responsible for the build of gas and bloat – namely those high in FODMAPs – do alleviate symptoms associated with the digestive discomfort of this disorder. Additionally, the article called for more research into FODMAPs and gluten sensitivity to help identify more accurate cause-and-effect relationships. In turn, this would help improve upon many overly restrictive diets being used to treat IBS at the time of publication.

Gibson and Shepherd express a common challenge with dietary intervention to treat IBS. While people may report food intolerances or “allergies” and their willingness to simply remove foods from their diet to avoid symptoms, he reports that this often leads to an overly restrictive diet that could leave a patient nutritionally compromised.

Science is only just beginning to delve into precise food-specific cause and effect, pointing to FODMAPs as one set of GI symptom triggers; food chemicals, which require more attention; and gluten, which has a long-known causality with celiac disease, and more recent connection with non-celiac gluten intolerance. It was also stated that psychosocial factors are intricately involved in visceral hypersensitivity – which can lead to both overly-reactive physical response in the gut and overly responsive pain thresholds as they correspond to food triggers. Gibson and Shepherd report that while dietary interventions may alleviate symptoms of IBS, they are not a cure, and future research into each of these areas can shed more light on this challenging area.

Reference: Gibson PR, Shepherd SJ. Food Choice as a Key Management Strategy for Functional Gastrointestinal Symptoms. Am J Gastroenterol. 2012;107:657-66.

2. Low FODMAP Diet Reduces Gastrointestinal Symptoms in People with IBS

FODMAPs include many short-chain sugars abundant in foods and beverages – and are said to be one cause of the belly pains that people with Irritable Bowel Syndrome (IBS) experience. A Low FODMAP Diet has been effectively used to help reduce these symptoms and this research puts even more science-based evidence behind the dietary intervention. In this randomized controlled, crossover study of people with IBS, the Low FODMAP Diet was an effective first-line treatment for 70 percent of people with a significant reduction in GI symptoms, including abdominal pain, bloating, gas and dissatisfaction with stool consistency – by half.

This research provides high-quality science in a randomized, controlled, cross-over study comparing the Low FODMAP Diet with a standard Australian diet and the patient’s usual intake patterns. IBS symptoms were more than halved with the low FODMAP eating pattern, and demonstrated efficacy for 70 percent - a vast majority - of patients with IBS.

Participants were randomized to receive 21 days of a diet low in FODMAPs or 21 days of a diet containing FODMAP content of a typical Australian diet. Participants were blinded to the diets and almost all food was provided. After this 21-day diet, each participant entered a washout period of at least 21 days in which they resumed their usual diet and then crossed-over to the alternate diet. The second interventional diet was not commenced until the symptoms had returned to the same level as during the baseline period, as determined by direct questioning by a study investigator.

The results of the current study provide high-quality data to fill the science gaps. As symptoms were more than halved in IBS subjects and all measured symptoms were reduced to a level that arguably is considered good symptom control. The difference in symptoms between the 2 controlled diets was seen immediately and the greatest symptom control was achieved and maintained after 7 days of the Low FODMAP Diet. Interestingly, of the 70% of subjects who felt better on the Low FODMAP Diet, this encompassed subjects across all 4 subtypes of IBS.

Reference: Halmos EP, Power VA, Shepherd SJ, Gibson PR, Muir JG. A Diet Low in FODMAPs Reduces Symptoms of Irritable Bowel Syndrome. Gastroenterology. 2014;146:67-75.

3. Nutrition Management Strategies for Irritable Bowel Syndrome: Review Paper

A wide variety of diets and food elimination practices have become common to provide some relief from the classic symptoms people experience with Irritable Bowel Syndrome. This review provides a thorough examination of the literature on each option, highlighting those with scientific merit, such as the low FODMAP eating plan.

Therapeutic elimination diets such as the FODMAP elimination plan, lifestyle changes, and select nutraceutical supplements such as peppermint oil and Iberogast should be considered for integration into the IBS management plan. Both herbals improve global symptoms and abdominal pain. The role of probiotics and prebiotics is less clear at this time.

Further advances in subtyping IBS will lead to more targeted nutrition modulation of the gut microbiome and improved outcomes. Future studies on the influence of food and food-based nutrients on IBS are warranted.

Reference: Mullin GE, Shepherd SJ, Roland BC, Ireton-Jones C, Matarese LE. Irritable Bowel Syndrome: Contemporary Nutrition Management Strategies. JPEN. 2014;38:781-99.

4. Irritable Bowel Syndrome: A Clinical Review

This summary organizes what is known to-date about Irritable Bowel Syndrome including:

  • History and prevalence of IBS
  • Medical characteristics and tests used to diagnose and differentiate it from other disease processes
  • Treatment options for the patient with this condition

It is hopeful that the future of science in this area will continue to improve the medical understanding of the cause of this challenging and debilitating medical condition. This will also help develop more advanced medical and non-medical treatment options. Meanwhile, this review concludes that strongest options include treating each patient according to their individual set of symptoms and needs, including interventions that may include diet, lifestyle, medical and behavioral options.

Clinical review points:

  1. IBS remains an enigmatic cause of significant distress, morbidity, and disability. IBS is a common, symptom-based illness defined by the presence of abdominal pain or cramping in association with constipation, diarrhea, or both.
  2. The diagnosis of IBS can be confidently established with the use of symptom-based criteria, the exclusion of concerning features, and the judicious use of diagnostic testing.
  3. Concerning features that should prompt a more detailed evaluation include new onset of symptoms after age 50 years; unexplained weight loss; a family history of organic gastrointestinal diseases such as colon cancer, inflammatory bowel diseases, or celiac disease; gastrointestinal blood loss; and unexplained iron deficiency anemia.
  4. Successful management of patients with IBS begins with a trusting, positive, patient-physician relationship.
  5. A holistic approach that embraces lifestyle changes, dietary interventions, medications, or behavioral strategies offers the greatest likelihood of sustained treatment benefit.

Reference: Chey WD, Kurlander J, Eswaran S. Irritable Bowel Syndrome: A Clinical Review. JAMA. 2015;313:949-958.

5. Low FODMAP Diet First Dietary Approach for Irritable Bowel Syndrome: A Review

This article provides a detailed review of 31 original research studies and 9 reviews, and summarizes the latest evidence to manage suspected food intolerance in IBS, including FODMAPs. To date, foods are not considered a cause, but rather symptom-triggering factors for IBS. Until a medical cure can be clarified, specific dietary elimination strategies, including the Low FODMAP Diet, can allow for some relief and improved quality of life for the person dealing with irritable bowel syndrome. The Low FODMAP Diet does improve symptoms in many (but not all) patients with IBS, and it is therefore recommended as a first-line dietary approach. It has been shown to be particularly effective with the support of FODMAP trained dietitians, who can ensure it is carried out properly.

Additional research on biomarkers that can help identify food intolerance and non-IgE mediated food allergy are needed. In addition to carbohydrates, which are being studied in detail through the FODMAP research, dietary fats and chemicals are called out as needing more attention in this area. It is also noted that the support of a nutrition professional can help ensure the Low FODMAP Diet is carried out properly, and monitored for nutritional adequacy over time.

Reference: Mansueto P, Seidita A, D’Alcamo A, Carroccio A. Role of FODMAPs in Patients with Irritable Bowel Syndrome: A Review. NCP. 2015;30(15):665-82.

What Are FODMAPs?