LESSON 6

Dietary Therapies

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Dietary Therapies for IBS

Dietary therapy plays a major role in IBS management. Food is a common trigger for IBS and many patients with IBS relate symptoms to eating. Research has shown that dietary interventions can be helpful in managing IBS symptoms, and many patients prefer dietary therapy to medications for IBS management.

Identifying specific food triggers is an important aspect of dietary management, although this can be challenging in practice. Food triggers can vary significantly from individual to individual. For some people, there are specific foods that worsen their symptoms, such as onions or garlic. In those cases, a recommended dietary strategy is to avoid the trigger foods. However, for some patients, eating in general can exacerbate symptoms due to an oversensitized gut. This can lead to a cycle of eliminating more and more foods, over-restriction, and fear around foods, which is common among patients with IBS.

It's important to understand that not all patients will respond to the same dietary strategy. Finding the right dietary approach that avoids over-restriction and food anxiety can take time and commitment. Below, we will review common approaches to dietary therapy for IBS, common misconceptions, and our expert guidance regarding dietary management for IBS.

The Low FODMAP Diet

The most commonly recommended diet for IBS is the low FODMAP (fermentable oligo-, di-, and monosaccharides and polyols) diet. FODMAPs are different groups of carbohydrates that share some important traits:

They are poorly absorbed in the small intestine.
They are rapidly fermented by gut bacteria.
They are highly osmotic, meaning they draw water into the bowel.

Due to these properties, FODMAPs can cause symptoms such as pain, gas, bloating, diarrhea, and constipation, especially in patients with IBS.

There are five main groups of FODMAPs to be aware of:

FODMAP type	High FODMAP food examples
Fructans	Wheat, rye, onion, garlic, artichoke, leek
Galacto-oligosaccharides (GOS)	Legumes (beans, lentils, chickpeas), cabbage, brussel sprouts
Lactose	Milk, yogurt, ice cream, soft cheeses
Fructose	Apple, pear, mango, watermelon, honey, high-fructose corn syrup, agave, sugar snap peas, asparagus, fruit juice
Polyols (sorbitol, mannitol, xylitol, maltitol)	Stone fruit (apricots, peaches, cherries, plums), apples, pears, blackberries, mushrooms, cauliflower, sugar-free gum and candy, artificial sweeteners

It is important to understand that FODMAPs are not inherently bad or unhealthy. However, for some individuals, certain FODMAPs can trigger IBS symptoms, depending on the type and amount eaten. Not every patient with IBS will have symptoms with every type of FODMAP. Research suggests that patients with IBS are typically intolerant to only 1-2 types of FODMAPs. Approximately 75% of patients with IBS will report improvement with the low FODMAP diet; which leaves about 25% who will not experience significant benefit.

The low FODMAP diet consists of three phases.

Phase 1: Elimination or Restriction — During this phase, all high-FODMAP foods are eliminated from the diet. This phase should last 2-6 weeks. The goal of this phase is to see if symptoms improve with the elimination of FODMAPs. If there is no improvement in symptoms, there may be hidden FODMAPs not eliminated, or the patient may be a non-responder (approximately 25% of patients).
Phase 2: Reintroduction — During this stage, each FODMAP group is reintroduced one by one. This helps identify specific foods that trigger symptoms. Current evidence suggests that most people will have 1-2 trigger categories of FODMAPs.
Phase 3: Personalization — Using information on specific triggers identified in Phase 2, the goal of this step is to reintroduce non-trigger foods and develop a diet plan that limits symptoms and is the least restrictive. Additionally, for foods that are triggers, developing strategies such as limiting amounts consumed, changing preparation, or using digestive enzymes targeted towards breaking down FODMAPs can help avoid complete elimination from the diet.

The low FODMAP diet is not about cutting out all FODMAPs forever — it's a structured, short-term tool that helps identify individual triggers and then use that knowledge to build a personalized, sustainable plan. The low FODMAP diet is challenging to implement and requires specialized knowledge about specific foods and preparation methods. For this reason, experts recommend implementing the low FODMAP diet under the guidance of a registered dietitian.

NICE Guidelines

Not every IBS patient needs to follow the low FODMAP diet. For many patients, it may be too restrictive or simply unnecessary. Most experts and clinicians recommend implementing a simple set of dietary changes as a first step prior to trying the low FODMAP diet.

These dietary changes are referred to as the NICE guidelines, developed by a UK-based organization, the National Institute for Health and Care Excellence, which provides evidence-based guidance and quality standards to improve health. Research has shown that implementing these dietary changes can improve IBS symptoms in up to 40% of patients.

NICE Guidelines for IBS

Avoid large meals

Large meals are more likely to trigger the gastrocolic reflex which can cause cramping and urgency.
Eat regular, evenly spaced meals

Skipping or leaving long gaps between meals can disrupt the normal pattern of gut contractions exacerbating IBS symptoms.
Eat slowly and chew food thoroughly

Eating slowly prevents excess swallowed air, a potential cause of gas and bloating. Chewing food thoroughly helps get a head start on digestion.
Limit caffeine, alcohol and carbonated drinks

Caffeine, alcohol and carbonated beverages can exacerbate gut symptoms such as cramping, diarrhea and gas.
Limit fatty foods and resistant starches

Fatty foods are more likely to trigger an exaggerated gastrocolic reflex leading to cramping and urgency. Resistant starch, commonly found in beans and legumes, resists digestion in the small intestine and then ferments in the colon causing gas and bloating.
Adjust fiber — more soluble, less insoluble

Soluble fiber forms a soft gel that can help regulate bowel movements, while insoluble fiber increases gut motility and gas which can worsen symptoms.

Gluten-Free Diet

The gluten-free diet is a popular diet that many patients with IBS try. However, the evidence behind gluten-free diets as a treatment strategy for IBS is limited. Gluten is a protein which is found in wheat, barley, rye, and related grains. Patients with celiac disease, an autoimmune condition, genetically predisposed, and triggered by gluten, are recommended to follow a gluten-free diet. Celiac disease affects 1% of the population.

Approximately 2% of the population will have non-celiac wheat sensitivity or non-celiac gluten sensitivity. These are individuals who experience symptoms when eating gluten but do not have evidence of celiac disease on laboratory testing or biopsies of their small intestine. Avoiding gluten will also improve their symptoms.

For those with IBS or other disorders of gut brain interaction, removing gluten can sometimes help reduce symptoms, but it is rarely sufficient to manage symptoms. Interestingly, many of the same grains that contain gluten also contain fructans, which are one of the high FODMAP sugars. Research suggests fructans are the FODMAP group most likely to trigger IBS symptoms. A 2018 study found that among individuals who reported sensitivity to gluten, fructans were most likely to induce symptoms, while gluten was no more likely than placebo to induce symptoms. Based on this evidence, most experts believe that many individuals who report symptom relief with gluten elimination are in fact experiencing the benefit of reducing fructans in their diet.

Finding a GI Dietitian

We have more resources on finding a GI dietitian and dietary therapy in our resources page.