A Low FODMAP Diet for Gut Health

Is a low FODMAP diet effective for chronic fatigue syndrome when there is also irritable bowel syndrome. Learn which foods are high in FODMAPs.

IBS is Common in ME/CFS and other Chronic Diseases

Bowel complaints are common to ME/CFS, fibromyalgia, and autoimmunity. A recent cohort study of ME/CFS, showed that 38% of those with ME/CFS experienced IBS. This figure proved to be about 10% higher than IBS prevalence in the general population. Some studies show even higher percentages depending on the diagnostic criteria used. A dietary change is the more effective in tackling IBS than any other medications or interventions. IBS, then, is very treatable.

What is a FODMAP?

FODMAP is a clever acronym for a complicated term: fermentable oligo-di-mono-saccharides and polyols. These are plant foods that are poorly digested or undigested by the human gut. Because FODMAP foods are poorly absorbed in the gut, they lend themselves to easy fermentation by the microbiome. The effect these foods have in the gut are increasing small intestine water volume, colonic gas production, and intestinal motility. These manifest as bloating, abdominal distension, loose stools, and cramping.

Let’s break it down. Fermentable oligo-di-mono-saccharides and polyols…

The oligosaccharides include fructans and galacto-oligosaccharide (GOS). These have the longest chain length and the body does not contain enzymes to digest them.  Foods high in oligo’s include:

  • Wheat and rye

  • Legumes

  • Nuts

  • Artichokes

  • Onions & garlic

The disaccharide lactose is problematic. Lactose can be broken down by the enzyme lactase in most individuals but this ability is dependent on genetic factors, age, and intestinal inflammation. Foods highest in lactose include:

  • Milk

  • Young and soft cheeses

  • Ice cream

  • Sour cream

The monosaccharides include fructose. This simple sugar is poorly absorbed across the entire small intestine and promotes water into the bowel lumen. Foods rich in fructose include:

  • Apples and pears

  • Watermelon

  • Mango

  • Honey

  • Sugar snap peas

The polyols are mannitol and sorbitol, and also artificial sweeteners such as xylitol and isomalt. Foods high in polyols include:

  • Apples, pears, & stone fruits

  • Cauliflower

  • Mushrooms

  • Snow peas

The Best Diet for IBS

Several randomized-controlled trials of the low FODMAP diet have been assessed for those with IBS. The diet has a proven track record for IBS, and is now a first-line diet option for those with IBS. After FODMAP restriction for 4-6 weeks, 75% or more of IBS patients will experience symptom relief. I’d suspect those that don’t respond favorably to such a diet have undiagnosed gut problems. A proper assessment of digestive health should include ruling out Celiac disease, Crohn’s, ulcerative colitis, diverticulitis, pancreatic or gallbladder insufficiency, and intestinal infections.  

IBS: Beyond the Gut

Irritable bowel syndrome can extend beyond the gut to effect other systems. Sleep trouble is estimated to be 28–74% in those with IBS patients. Others may also experience urinary symptoms (i.e., frequency, urgency, waking at night, incomplete bladder emptying sensation). Still others experience wide-spread pain or skin conditions. The overlap between intestinal disorders and systemic manifestations is yet to be fully uncovered. Clues point to the brain-gut axis, microbial and immune system interaction, histamine release, and other factors.  

A small study of 38 fibromyalgia patients, undertook a low FODMAP diet for 4 weeks. All fibromyalgia symptoms, including wide spread pain, reduced following the dietary change.

Could a dietary change not only improve gut symptoms, but also more?

How to Reduce FODMAPS

For a period of 4-6 weeks, eliminate all FODMAPs from the diet. It is helpful to keep a written record of foods and symptoms during this period to better assess the efficacy of the restriction. This is also a good way to ensure hidden FODMAPs are not entering the diet. After the end of the trial, reintroduce FODMAPs to the diet slowly. Start with lesser fermentable foods—onions, mushrooms, and garlic—and allow enough time to assess their effects. Gradually reintroduce more fermentable foods—cauliflower and legumes, and lastly fruits—to determine if there is persistent individual sensitivity.

But…FODMAPS are Good for the Microbiome

Actually, yes. Some FODMAPs are food for the gut microbiome. The oligosaccharides mentioned above are also called prebiotics. These foods tend to promote bifidobacteria in the gut, a bacteria generally associated with positive health outcomes. A low FODMAP diet, and all other diets actually, are not intended to be forever. Even a short course of a low FODMAP diet can reduce bifidobacteria populations. FODMAP elimination may be required for longer periods in the most severe IBS cases or in those with IBD, like Crohn’s. For others, short courses of low FODMAP diets may provide a tool that can be instituted during periods of severe symptoms. Supplementation with a broad-spectrum probiotic is a good idea to bolster bifidobacteria.

As always, I’m here to help with your dietary strategies. Book some time now.


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Schumann, D., et al. (2018). Low fermentable, oligo-, di-, mono-saccharides and polyol diet in the treatment of irritable bowel syndrome: A systematic review and meta-analysis. Nutrition, 45, 24–31.

Catassi G et al. (2017) The Low FODMAP Diet: Many Question Marks for a Catchy Acronym. Nutrients. 9(3).

Barrett, J. S. (2017). How to institute the low-FODMAP diet. Journal of Gastroenterology and Hepatology, 32, 8–10.