Chances are, you’ve heard of irritable bowel syndrome, but why should you care? Understand this chronic and often debilitating disorder that affects an estimated 8-20% of our population, but remains undiagnosed and untreated for most.


Irritable bowel syndrome (IBS) is a condition that involves recurrent abdominal pain, cramping, constipation and/or diarrhea. The enteric nervous system (ENS) is involved in controlling the gut so when our ENS is out of tune, it impacts how the gut moves and deals with food. So what causes the ENS to go haywire? Known contributing factors include:

  • Genetics
  • Gut infections
  • Abnormal balance of bacteria, stress, and abnormal colonic fermentation and sugar malabsorption.

In particular, there is a group of carbohydrates (sugars) known to be poorly digested, causing gas and abdominal distention when they are fermented by bacteria, called FODMAPs. FODMAP is an acronym for Fermentable Oligosaccharides, Disaccharides, Monosaccharides And Polyols. Common high FODMAP foods contain:

  • Fructose: A simple sugar found in fruits and some vegetables such as stone fruits, apples, pears, and garlic. Fructose is also highly concentrated in honey and high fructose corn syrup.
  • Lactose: A carbohydrate found in dairy products like milk or cheese
  • Fructans: Found in foods such as wheat, garlic and onions.
  • Galactans: Found in large amounts in legumes.
  • Polyols: Sugar alcohols such as xylitol, sorbitol and mannitol.

In the pioneering study at Monash University, researchers developed a low FODMAP diet to understand whether it can improve symptoms in people suffering from IBS. The study had two goals:

  1. Determine whether symptoms improved when fructose was removed from the diet
  2. Determine whether any improved symptoms were related to fructose only or FODMAPs in general.

Patients were randomly given either fructose, fructans, a mixture of the two, or glucose (low FODMAP) as drinks with meals for a maximum test period of 2 weeks. What they found was that patients with IBS and fructose malabsorption had symptomatic improvement from restricting FODMAPs in general from their diet.

Studies show that  ~75% of people with IBS can benefit from a low FODMAP diet and will experience great improvements in common symptoms, including diarrhea, constipation, bloating, abdominal pain and gas.  It is important to note, however, that following a low-FODMAP diet is not a cure for IBS, and individual response to the diet will vary.  Another important aspect to consider is that the diet’s efficacy also varies because of the lack of defined quantitative values for high vs. low FODMAP foods. Furthermore, the diet is considered challenging for most patients to follow because it is restrictive in what one can eat.

Unfortunately, it is still not well understood why some people get IBS, and both testing and treatment options are limited. IBS is considered a functional disorder, meaning that it is a condition that affects the normal functions of the body with no physical explanation from a screening test. However, there is new research indicating promising results that a new diagnostic test may soon be developed. 

Until there is a more definitive testing method, physicians face a difficult task in first ruling out other reasonable causes since the symptoms of IBS are not unique to the disorder. For those reasons, it is always recommended for you to see your physician before reaching out to a Registered Dietitian who has undergone training to help you implement a low FODMAP diet.


Haley Goodrich, RD, LDN is a private practice Registered Dietitian based in Pittsburgh, PA inspiring others to have a healthy relationship with food.  Specializing in disordered eating, intuitive eating, and GI disorders, Haley’s mission is to show that healthy doesn’t have to be restrictive or defined by how you compare to others. To stay inspired to be your healthiest you, visit Haley at INSPIRD Nutrition.