A GI tract floats in the middle as fibrous foods (lit up like neon signs) swoop and move behind it.

Navigating Fiber with IBS: Types, Amounts and How to Get Enough

By now, most of us are aware that fiber plays a big role in how we poop. However, this doesn’t always translate to us getting enough fiber! We are busy people with busy lives, so thinking about fiber isn’t always at the top of our to-do list. That’s why today I want to discuss fiber and how to consume the best types of fiber for IBS in a practical way!

How does fiber help with bowel movements

Sure, you’ve likely heard fiber helps you poop. But how? To put it quite simply, fiber plays three main roles in your digestive system:

  1. Maintaining gut motility (how quickly things move through our gut)
  2. Maintaining appropriate stool consistency
  3. Feeding your gut bacteria - which help with consistency, motility (and more!)

We need quite a bit of fiber each day. Women should aim for 25 grams per day and men 38 grams. Research shows that many North Americans struggle to hit these targets and generally only consume about 15 grams per day! Fiber comes from plant-based foods such as whole grains, vegetables, fruit, pulses, nuts, and seeds. These foods consist of two types of fiber, each of which contributes to digestion in a unique way.

Soluble fiber

This type of fiber dissolves in water and forms a gel. This action helps to absorb water in the bowel and subsequently helps to create soft, well-formed stool. Soluble fiber simultaneously helps to soften stool in constipation-dominant IBS and decreases diarrhea in those with IBS-D.

This type of fiber can also help to lower cholesterol levels and regulate blood sugars. A win for everyone!

Where to find soluble fiber: oats, legumes, oranges, psyllium husk, nuts, seeds, and bananas

Insoluble fiber

Unsurprisingly, insoluble fiber is the opposite of soluble fiber; it does not dissolve in water and therefore does not create a gel that helps bind stool. However, insoluble fiber is still very useful! It plays an important role in keeping digestion moving by increasing motility in the digestive tract and adding bulk to stool.

Where to find insoluble fiber: skins of fruit, shells of seed, and wheat bran

IBS and fiber

Fiber is a very important aspect of managing irritable bowel syndrome. Fiber can both improve and exacerbate symptoms, depending on specific fiber type and each individual’s tolerance levels.

Certain subtypes of dietary fiber called ‘fermentable fibers’ have been shown to help alter the gastrointestinal microbiota, leading to a potential increase in good gut bacteria or “probiotics.” These dietary fibers are the food that our gut bacteria feed on, making them a crucial part of maintaining overall gut health. These kinds of fibers are referred to as prebiotics. Promoting a healthy gut microbiota is key in the prevention of diseases, energy and mood regulation, cardiovascular health, and much more.

That being said, some high fiber foods contain more FODMAPs (highly fermentable carbohydrates) than others. Highly fermentable fibers may worsen symptoms in some IBS patients, depending on their tolerance to specific FODMAPs. In fact, many of our prebiotic-rich foods contain FODMAPs in the form of galacto-oligosaccharides (GOS) and/or fructans. These types of carbohydrates are shown to contribute to increased gas production, bloating, and GI discomfort in many individuals with IBS. Some examples of foods that contain GOS include beans, chickpeas, cashews, pistachios, and soybeans. Foods high in fructans include wheat, rye, barley, inulin, chicory root, onions, and garlic.

It is important to note that not everyone with IBS will need to avoid foods high in GOS and fructans. Elimination is dependent on each person’s symptoms, and where they are on their IBS management path. If you are just starting out on a low FODMAP diet, you will likely benefit most from avoiding these foods. However, if you have reintroduced FODMAPs and are tolerant to GOS and/or fructans, you can certainly liberalize your diet to include these foods. In fact, adding these foods back to upper tolerable amounts is very important for feeding those good gut bugs!

So what happens if you are NOT tolerant to GOS and fructans? Keep including small amounts, especially when your IBS symptoms are under control - for example, when you are less stressed.

How to get enough fiber during FODMAP eliminations and beyond

The elimination phase of the low FODMAP diet can certainly limit your access to dietary fiber, simply because of the narrowed amount of foods to choose from. However, there are lots of fantastic low FODMAP foods that pack a BIG punch when it comes to fiber.

Some of my patients’ favorite sources of FODMAP-friendly fiber include: bananas (no brown spots), chia seeds, berries, mixed nuts, oats, quinoa, and canned lentils.

What about fiber supplements?

Although it is possible to get enough fiber from food alone, it can still be a struggle for some people! A fiber supplement is often a great option to help give that final push toward the recommended 25-30 grams.

Fiber supplements on the market are primarily made from soluble fiber; the type that creates a gel and helps to yield soft, yet formed stool. However, the source of the fiber varies amongst products, making some more appropriate for IBS.

Psyllium Husk

Studies show this type of fiber provides symptom relief in both constipation and diarrhea-predominant subtypes of IBS. It is often very well tolerated in IBS.


This type of fiber is high in fructans and therefore could potentially lead to more gas, bloating, and abdominal pain in those with irritable bowel syndrome. This is generally not recommended, especially during the elimination phase of the low FODMAP diet.

Partially hydrolyzed guar gum

This type of fiber supplement is low FODMAP and has shown symptom relief in IBS patients.


This type of fiber is non-fermentable, therefore does not generally have side effects such as gas production, bloating, or pain. It may be especially useful for those with IBS-C as it helps to soften stool with its gel-forming properties.

As you can see, there are lots to consider with dietary fiber in irritable bowel syndrome - type, amount, and tolerance level. It may feel like your head is spinning! If you need help figuring out your fiber needs and which foods and/or supplements are appropriate for you, consult with a dietitian, physician, or pharmacist to learn more!

At the end of the day, fiber is considered a low-risk strategy in IBS management. It is non-systemic and easy to experiment with in a safe way in most cases. It may be just the thing you need to round out your IBS toolkit!

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