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Do Individualized Diets Work for Irritable Bowel Syndrome (IBS)?

Bloating. Gas. Constipation. Abdominal Pain and Discomfort. Loose or Frequent Stools. All different manifestations of Irritable Bowel Syndrome, or IBS, which at this point in time is diagnosed through exclusion of other gastrointestinal disorders. IBS is infamous for decreasing ‘quality of life’ for those affected, making it difficult to leave the house, maintain a regular work schedule, or go out to eat with family and friends (source, source).

What Does Diet have to do with IBS? Well, it turns out, quite a bit. An an integrative dietitian nutritionist, I am always thinking in terms of ‘root cause’ versus just symptom control. From my viewpoint, understanding the diet-IBS link starts with breaking down what is happening in IBS.

A 2015 article in JAMA (Journal of the American Medical Association) outlines factors important to the development of IBS, as follows:

  • alterations in the gut microbiome
  • intestinal permeability
  • gut immune function
  • motility
  • visceral sensation
  • brain-gut interactions

In other words, Irritable bowel syndrome can not be explained by one single ‘ cause’ or ‘mechanism’ (although post-infectious IBS is not uncommon), meaning that an integrative, comprehensive approach makes a lot of sense. Let’s briefly talk about a couple of nutrition principles that you might be familiar with when is comes to diet and IBS: the Low-FODMAP diet and Food Sensitivities.

The Low-FODMAP Diet: If you’ve been reading about diet and IBS, you’ve likely come across the low-FODMAP diet more than once. I have a number of individuals contact me about low FODMAP diets, hoping that they can use the approach to decrease their symptoms and to feel better. If you aren’t familiar with the acronym, FODMAP stands for Fermentable Oligo-, Di- Mono- Saccharides and Polyols, a reference to fermentable carbohydrates that are either poorly absorbed and draw fluid into the small intestine (osmotic load) or from being rapidly fermented from the microbiota, leading to increased gas from the ‘byproducts’ of fermentation. Think of fermentation as the byproduct of fiber being ‘eaten’ by the bugs in your gut. Not all FODMAPs exacerbate abdominal symptoms in patients with IBS, and different individuals differ in the amount of FODMAPS that they can tolerate! It’s even been shown that those who DO respond to a FODMAP diet have a different mix of gut bacteria than those who do not (source), a testament that the type of bacteria in your gut play a role in how you digest and break down various substances.

The presence and degree of abdominal symptoms in a given individual depends on the degree of malabsorption experienced by the individual. Here’s the thing, though-recent trials have shown that the low-FODMAP diet is associated with marked changes in gut microbiota, specifically reduction in microbiota with prebiotic properties ​​(source), and especially reduction in luminal Bifidobacteria concentration- a strain that we don’t want depleted in the context of IBS!

“Although inulin-type fructans and galacto-oligosaccharides are FODMAPs, the ingestion of which may be associated with abdominal symptoms, they are also prebiotics, stimulating the growth of beneficial bacteria. Studies have shown reduced total bacterial abundance and reduced concentration of bifidobacteria following a low FODMAP diet, suggesting potential adverse health effects of the diet (source).

For these reasons, I do not talk about a low-FODMAP diet as a ‘treatment’ for IBS, but rather a short-term management strategy (which can sometimes be done through an adapted approach versus a low-FODMAP diet in it’s entirety by a skilled dietitian) to glean some information about digestive challenges that an individual is having. In some cases, for instance, where an individual is taking in more fructose (fruit sugar) than their body has an available ‘shuttle’ for, simple shifts can be made that maintain nutrient content of the diet, as well as which continue to promote microbial diversity (a decent discussion of the micro biome is beyond the scope of this post, but consider that a good thing!).

Inflammation + Food Sensitivities: Let’s talk about ‘inflammation’. Chronic low-grade mucosal inflammation has been frequently observed in many studies of IBS patients and in animal models of IBS . proportion of IBS (source)(source). The mix of microbes in the microbiota and foods that someone is sensitive to or allergic to, could fuel low-grade inflammation and altered gut permeability. There are lots of things to think about with diet when it comes to inflammation! Let’s take one: food sensitivities, which involve the immune system. Through different pathways than a classic allergy, non-IGE immune driven pathways can cause a whole host of chemicals including Histamine, Prostaglandins, Leukotriences, Cytokines, Dopamine, and others.

Just a few months ago, a randomized controlled trial of individualized diets for IBS based on a ‘leukocyte activation’ test was completed. What the heck is a leukocyte activation test? In brief, it is a food sentisitivty test which uses whole blood samples to measure reactions to foods and food chemicals, in turn allowing an individual to understand which foods are eliciting an inflammatory reaction. This study used a test called the ALCAT (which has since been improved upon by the same immunologist who developed ALCAT. His new methodology is used as the MRT-Mediator Release Test; more about the differences here).

On to the results: Over four weeks, individuals were randomized to individualized guidance for eliminating foods with positive assay results based on food sensitivity results compared to a diet where those foods were not restricted (matched ’sham’ diet). Depicted below are changes in the IBS Global Improvement Scale (GIS) as well as the IBS Symptom Severity Scale (SSS):


Yes, you are seeing DOUBLE the improvement for the group that had followed a diet based on testing results.

According to the authors: “In summary, this study provides data suggesting that a leucocyte activation test can be used to develop an individualised diet that can alleviate symptom burden in IBS. These dietary changes may be less restrictive than a low-FODMAP diet, and may result in better long-term adherence.” (source)

If you’ve been struggling with symptoms of Irritable Bowel Syndrome, could it be time to explore how modifying your diet would help?

Summary: My Approach to IBS

Here are the current pillars of my approach to addressing IBS, individualized built off of a thorough history and designed to accommodate individual goals and preferences:

  • Addressing Food Sensitivities
  • Managing Food Intolerances (think-digestive versus immune system mediated)
  • Decreasing Inflammation + ensure support for resolving inflammation
  • Modifying Fermentable and Soluble Fiber types as appropriate
  • Remaining mindful of microbial gut diversity
  • Ensuring proper mineral balance for healthy peristalsis
  • Modifying food preparation to minimize intolerances + increase absorption
  • Stress Management + Sleep
  • Nutraceuticals to decrease visceral hypersensitivity and facilitate digestion
  • Focus on Repairing/protecting gut barrier function

About Sarah Ferreira

Sarah Ferreira,MS,MPH,RD,CDN,CNSC,IFNCP,CHWC is a Registered Dietitian Nutritionist with complementary certification as an Integrative and Functional Nutrition Certified Practitioner and Certified Health and Wellness Coach. She is the owner of Mindfully Nourished Solutions, where she uses a whole-person, whole-food approach to explore the impact of nutrition on mood and cognition. Her individualized approach integrates an assessment of nutritional, genetic, environmental, and lifestyle factors into a collaborative nutrition care plan using cutting-edge research designed to facilitate meaningful and restorative changes based around client goals and priorities.

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