If you're one of the millions of people who suffer from digestive issues like Irritable Bowel Syndrome (IBS), you may have heard about the low FODMAP diet. But what is it, exactly? And how does it work? In this blog post, we'll find out who should consider a low FODMAP diet, why these types of foods can cause problems in some people, and how to try a low FODMAP diet for beginners in a safe way.

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What are FODMAPs?

FODMAP stands for four types of fermentable carbohydrates: oligosaccharides, disaccharides, monosaccharides, and polyols.

FODMAPs move through the digestive tract to the large intestine, where they are digested by naturally-occurring gut bacteria. The acronym is a collective name for short-chain carbohydrates and sugar alcohols that are found in many common foods, including:

fruits (apples, pears, mangoes)
vegetables (garlic, onion, leeks)
grains (wheat, rye, barley)
dairy (milk, yogurt, ice cream)
legumes (chickpeas, lentils, kidney beans)

FODMAPs are also a key source of prebiotic fiber for your gut bacteria.

Why do FODMAPs cause problems?

The 'F' in FODMAP stands for fermentable, and this means your digestive bacteria ferment these starches to produce various by-products like butyrate and other protective compounds.

However, along with beneficial byproducts, FODMAPs also produce gas as they ferment, as well as draw water to the intestines. And although FODMAPs are not the direct cause of digestive disorders such as IBS, they can trigger gastrointestinal symptoms in some people, especially those with IBS or other functional gastrointestinal disorders.

When FODMAPs reach the colon (large intestine), bacteria ferment the FODMAP molecules to produce hydrogen and methane gasses. The gas distends—or stretches—the intestine and puts pressure on nerves surrounding the digestive organs (1).

For many people with IBS, the nerves of the gut are quite sensitive to changes in pressure or volume, and this is what triggers gastrointestinal symptoms (2). Foods high in FODMAP carbohydrates can trigger digestive discomfort for anyone when consumed in large amounts, but much smaller portions can worsen symptoms for those with IBS.

Read: Stress, Anxiety, and IBS

How Does the Low FODMAP Diet Work?

The low FODMAP diet is a temporary elimination diet that removes high FODMAP foods from your diet, usually for about 6 to 8 weeks. Then, you’ll slowly reintroduce FODMAP foods and watch for any symptoms. This allows you to identify which foods are problematic for you, and which ones you can tolerate in reasonable amounts.

A low FODMAP diet can be practiced in 3 phases:

Phase 1 (2-6 weeks): FODMAP elimination - Identify and remove the high FODMAP foods from your diet that are aggravating symptoms. You can replace high FODMAP food with low FODMAP foods. Many people start to feel better as early as two days into the elimination phase.
Phase 2 (6-8 weeks): FODMAP reintroduction - Gradually reintroduce individual high FODMAP foods back into your diet, working through the list of each FODMAP category. Your overall diet should still remain low in FODMAP foods, while reintroducing each food separately to detect symptoms. If no symptoms occur, the food can be reintroduced; if symptoms are present, you may need to remove it from your diet permanently.
Phase 3 (ongoing): Personalization & symptoms management - Once you and your dietitian establish which foods trigger your symptoms, you can reintroduce some foods, and avoid only those that aggravate your gut.

This should allow you to find a balance with healthy foods that also don't trigger digestive symptoms. Many high FODMAP foods are great for your health, but large amounts of them are not good for your gut if you have IBS or other digestive troubles.

Before beginning any elimination diet, consult a qualified functional medicine practitioner.

Who should avoid FODMAPs

The low FODMAP diet is a functional treatment option for those with IBS and SIBO. Research has found that it reduces symptoms in up to 86% of people (3).

Because any type of elimination diet can be quite restrictive, it’s important to work with a qualified functional medicine doctor or dietitian, who can monitor your health and provide the proper medical advice. If you have trouble managing IBS symptoms, or feel any of the following after eating, consult your integrative doctor for guidance.

Bloating
Excessive gas
Stomach pain, cramps
Diarrhea
Constipation
Feeling like you have a 'full' stomach after eating only a small amount of food

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A low FODMAP diet isn’t right for everyone

A low FODMAP diet isn’t recommended for those who do not have irritable bowel syndrome, SIBO, or other functional GI disorders. If you’re struggling to manage digestive symptoms, speak with a qualified holistic doctor or nutritionist to identify which foods trigger symptoms, and how to proceed safely.

The low FODMAP diet also may not be the best course of action for those with Celiac disease, because gluten is a protein—not a carbohydrate—so some low FODMAP foods still contain gluten. However, a low FODMAP diet may be beneficial for those with non-Celiac gluten sensitivity if it’s the FODMAPs in wheat that are a trigger, for example. This type of restrictive diet is also not recommended for those with any type of disordered eating, or those who are underweight.

Work with a qualified holistic nutritionist to build the right diet for you.

FODMAPS & Celiac disease

A low FODMAP diet is not necessarily a gluten free diet. However, the low FODMAP diet does remove most sources of gluten such as wheat, rye, and barley. This explains why some people who have a gluten intolerance feel better when omitting high FODMAP foods, when it’s actually the removal of gluten reducing symptoms.

The low FODMAP diet may not be the best course of action for those with Celiac disease, because gluten is a protein—not a carbohydrate—so some low FODMAP foods still contain gluten. However, a low FODMAP diet may be recommended for two main reasons relating to gluten sensitivity and/or Celiac disease (4):

You have been diagnosed with or suspect a non-celiac gluten intolerance.
You have been diagnosed with celiac disease, but still experience gas, bloating, or other digestive symptoms after avoiding gluten

Read: How Do I Know if I Have a Food Intolerance?

Symptom overlap with IBS and Celiac disease

Most patients with celiac disease are able to resolve their symptoms after following a gluten-free diet, but up to a quarter of those still experience gastrointestinal symptoms even after omitting gluten completely. There is a significant overlap between symptoms of celiac disease and IBS, including bloating, abdominal pain, diarrhea, and constipation. A low FODMAP diet may be a good option to resolve persistent IBS-like symptoms in those with celiac disease who are already gluten-free (5).

Low FODMAP diet and IBS

Studies show that 50% to 86% of patients have a “clinically meaningful response” to the low FODMAP diet (3). Researchers believe that a low-FODMAP diet is best for those with diarrhea-predominant IBS (IBS-D).

The reason that cutting out high FODMAPs foods is so effective at reducing and even eliminating gut symptoms such as bloating and abdominal pain is due to the removal of the fermentable food source responsible for drawing water and gas into the intestines.

For those who are sensitive to FODMAPs, the extra gas and water cause the intestinal wall to stretch and expand. Because people with IBS tend to have a highly sensitive gut, ‘stretching’ the intestinal wall causes exaggerated sensations of pain and discomfort.

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Low FODMAP diet in children with IBS

Approximately 5% of school-aged children have IBS, according to diagnostic criteria, and evidence has recently emerged for consideration of a diet low in FODMAPs when treating children with IBS. Digestive symptoms in children obviously have a significant negative impact on quality of life, education, and social development.

In one study involving 52 children, ages 7 to 17 years old, all the children who completed the study were found to have significantly fewer daily episodes of abdominal pain while following the low FODMAP diet, compared to the Standard American Diet (6). It’s worth noting that the children only followed the diet for 2 days. Maximum symptom improvement occurs in adults at about 7 days, so a longer trial may affect outcome as well (7).

Although popular belief links food intolerances to symptom generation and children report that certain foods exacerbate symptoms, there have been few controlled trials in pediatric cohorts.

Should you avoid FODMAP foods forever?

You should not follow a strict low FODMAPs diet for any longer than required. Any investigative diet (like low FODMAP) is designed to identify certain foods that trigger symptoms. There may be serious health side effects to following a very low FODMAP diet in the long-term, such as (8):

Decreased vitamin, mineral, and nutrient intake
Reduced types of gut bacteria, including Bifidobacteria
Reduced function of the mucous layer in the digestive system, resulting in inflammation
Low SCFA production
Dysbiosis

A high FODMAP food also contains prebiotic fiber, which is the primary fuel source for even the good bacteria that live in your gut. Here’s why you need prebiotic fiber.

Should you try a low FODMAP diet?

Many people can experience uncomfortable gastrointestinal symptoms when eating excess amounts of FODMAPs, so this kind of elimination diet can be a helpful step toward creating an effective diet plan to manage IBS symptoms. But, like all diet changes, you should be aware of the potential risks, such as changes to your microbiome. When trying an elimination diet, you should always work with a qualified holistic nutritionist or integrative doctor to monitor your health.

If you have IBS, Celiac disease, SIBO, or any other pre-existing gastrointestinal issue, or if you believe you may have an undiagnosed health issue, contact an integrative physician before starting any elimination diet, including the low FODMAP diet.

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About
the author

CentreSpring MD, formerly known as Atlanta Center for Holistic and Integrative Medicine, provides the best medical care by using an integrative approach to find a patient’s centre—their core—empowering them to spring forth into health.

Blog Reviewed By:

Dr. Taz Bhatia, M.D.

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What Is a Low FODMAP Diet & When Should It Be Used?