Great Gut Blog

Fiber and FODMAPs

Posted by Brad Dennis, Ph.D. on

Fiber and FODMAPs

We all know that fiber is good for us – but people who suffer from gastrointestinal disorders like Irritable Bowel Syndrome (IBS) can have trouble with fiber in their diet. For many, a low FODMAP diet has been found to help with the symptoms of digestive distress. Is there then a connection between fiber and FODMAPs? Yes, there is!

What are FODMAPs?

The acronym FODMAP stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols. Quite a mouthful – and may not really answer the question. FODMAPs are a group of short-chain carbohydrates that can contribute to the symptoms of gastrointestinal disorders. You generally only see the term in reference to a special diet that is low in these compounds in an effort to alleviate the symptoms of these digestive disorders and heal the gut.

Oligosaccharides include fructans and galacto-oligosaccharides. Foods high in these compounds include:

  • All members of the onion family: onions, leeks, and garlic
  • asparagus
  • lentils
  • chickpeas
  • green peas
  • lima beans, kidney beans and other legumes
  • wheat
  • jicama
  • dried dates, pineapple, raisins
  • grapefruit
  • persimmon
  • agave
  • artichokes

Monosaccharides and disaccharides are sugars. Monosaccharides are fructose, glucose, and galactose.  Disaccharides are lactose, which is a type of sugar found in milk and dairy products. As you’d expect, cane and beet sugar, and honey, are high in monosaccharides, as are many fruits (such as cherries, apples, grapes, watermelon, pears, and pineapple) and even some beans. Milk and cream, cheese, yogurt, butter and ice cream all contain high levels of both mono- and disaccharides.

Polyols are sugar alcohols, like xylitol, sorbitol, and mannitol. Polyols can be found in a variety of foods, including:

  • sweet potatoes
  • cauliflower
  • potatoes
  • avocadoes
  • watermelon
  • mushrooms
  • artificial sweeteners and sugar substitutes

Note: the above lists are not exhaustive. The Monash website is the best source for comprehensive lists of foods containing these substances.


At its most basic, the FODMAP diet is simply an elimination diet.

The FODMAP diet was devised at the Monash University in Melbourne, Australia, and is focused on reducing and eliminating these highly fermentable carbohydrates that can exacerbate digestive distress.

For the majority of people, a low FODMAP diet is supposed be a temporary thing. Like any elimination diet, the point is to eliminate all potential exacerbators of symptoms and then, slowly, reintroduce them one by one so as to identify the foods that trigger symptoms. Those are the only foods that should then remain out of the diet and be avoided. The remaining foods can – and should – be brought back into the diet. The result is a personalized diet that will allow a person to eat healthily without triggering digestive distress.

The Fiber – FODMAP connection

Why is fiber such a big deal when we start talking about FODMAPs? We talk about fiber’s health benefits a lot (of course), but in some cases, when someone is suffering from various digestive disorders such as IBS, fiber can actually worsen symptoms. That’s definitely not something anyone – including us here at Great Gut – want!

For those who have been following our blog for some time, the reason fiber can cause trouble with some people suffering from a digestive disorder is likely obvious: many of the foods that are high in one or more FODMAP compounds are also high in fiber and in particular, high in prebiotic fiber.

If you think these foods may be contributing to your digestive woes, you should see your doctor and ask whether an elimination diet such as FODMAP might be useful for you. Never experiment with a FODMAP diet without a doctor’s advice because fiber is an absolutely necessary nutrient for your body and a strict. Completely eliminating it could lead to severe constipation. Your doctor can help you create a proper elimination diet that will ensure you don’t tip the balance of the gut scales too far in the opposite direction (or make current symptoms worse, for those whose digestive woes already lean towards the constipation side of the pendulum).

For those who need to reduce or eliminate most FODMAPs, they find themselves in a conundrum: fiber is essential to healthy gut, so how to keep fiber in the diet while avoiding FODMAPs?


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