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Fiber and IBS: What You Need To Know

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Let me help clear up any misinformation on a sometimes confusing topic – fiber and IBS (Irritable Bowel Syndrome). In recent years fiber-rich foods, either naturally occurring or fiber fortified, have carried a bit of a health halo encouraging us to eat more to better our gut bacteria and improve our health.

While increased fiber is encouraged for the majority, not all fiber sources are well tolerated for those suffering with IBS. We cover the topic Fiber and Irritable Bowel Syndrome (IBS): What You Need To Know in this article.

Fiber and IBS: What you need to know

Does Increased Fiber Intake Help IBS?

For those with IBS-D (irritable bowel syndrome with diarrhea), you may be wondering if consuming more fiber will worsen your symptoms by increasing the frequency or urgency of your bowel movements.

Those with IBS-C may have experimented with a high fiber diet and/or a fiber supplement and actually felt worse.

It is not uncommon for health care providers to recommend a high fiber diet as nutrition therapy for IBS prior to the popularity of the low FODMAP diet. Oftentimes this broad stroke recommendation led to excessive FODMAP intake, worsening symptoms, specifically bloating, gas and abdominal pain.

Let me preface, fiber comes in many different forms and its properties greatly affect the function it has within the gut.

All fibers resist digestion, however only some are fermentable and those are more likely to provoke IBS symptoms. There are many gut-friendly fiber-rich foods to choose from that can actually help improve your IBS symptoms if you choose wisely.

What Exactly is Fiber?

By definition fiber is mostly indigestible material in food that stimulates the intestine to peristalsis and promotes elimination of waste from the large intestine. Understanding the difference between soluble and insoluble fibers is important.

Soluble Fibers

Soluble fibers dissolve in water, pull water into the stool, and form a gel like substance that helps move contents down the GI (gastrointestinal) track. Soluble fibers are found in many foods such as oats, strawberries, citrus fruit, rice, potatoes, beans, broccoli, and carrots.

Soluble Fiber Oats

Watch out for the prebiotic soluble fibers inulin and fructooligosacchharides (FOS), which are highly fermentable and best avoided since they may trigger IBS symptoms. These sneaky little ingredients are often added to protein shakes and bars, yogurts, probiotic supplements, fiber supplements and more.

You May Want To Read: IBS & Probiotics: Should I Take Them?  and All About Low FODMAP Meal Replacements and Protein Shakes

Inulin is naturally occurring in asparagus, chicory root, garlic, onions, and artichoke, which are all high FODMAP foods. Note that some of these foods do have low FODMAP serving sizes.

Read more in our article, High FODMAP Foods With Low FODMAP Serving Sizes.

Insoluble Fibers

Large, coarse insoluble fibers help regulate bowels in healthy individuals by irritating the lining of the large intestine inducing a bowel movement. These fibers are often referred to as roughage and add bulk to stool. Insoluble fibers pass through the GI tract without change.

Greens against a wooden background with the words Insoluble Fiber Greens

Not to be too visual, but think of the last time you ate corn and leafy greens? This fiber source can speed up gut transit time, which may be helpful for those with IBS-C, and no so helpful for those with IBS-D.

Insoluble fiber sources include wheat bran, nuts, seed hulls, kale, blackberries, cauliflower and fruit skins to name a few.

You May Want To Read: Top 5 High Fiber Low FODMAP Foods 

Why Fiber is Important!

Fiber is an essential nutrient for overall health as it provides benefits for a multitude of health conditions including IBS (when chosen correctly), cardiovascular disease, cancer, diabetes, weight management, and more.

Several fiber sources are considered prebiotics which stimulate the growth of the beneficial gut bacteria leading to a more diverse and healthier gut microbiome.

Fiber intake is often compromised when adopting a low FODMAP diet, which can have adverse effects on the beneficial gut bacteria and IBS symptoms. To exemplify, constipation may worsen if fiber intake plummets and this may negatively affect the results of your low FODMAP diet experiment.

[bctt tweet=”It is important to emphasize variety and frequent intake of low FODMAP fiber rich foods when embarking on a low FODMAP diet.” username=”FODMAPeveryday”]

It is important to emphasize variety and frequent intake of low FODMAP fiber rich foods when embarking on a low FODMAP diet. As a dietitian I like to take a “food first” approach, however fiber supplements may be helpful, especially if one is struggling to meet their fiber needs.

The DRI or “daily recommended intake” of fiber for adults is 25-38 grams per day (women should aim for 25, and men 38). The average adult consumes only 15 grams per day, a significant deficit. One must make an effort to consume fiber-rich foods at every meal and most snacks in order to hit this target goal.

Let’s break down why fiber is important for IBS-C, D, and M (IBS- mixed where one experiences both constipation and diarrhea).

Dog with glasses sitting on a toilet with a newspaper that reads:Fiber is crucial for regular bowels.

IBS-C & Fiber

Fiber is crucial for regular bowels. Prior to initiating the low FODMAP diet, I often recommend my patients strive to hit their fiber goal via whole foods and possibly supplements to see if this therapy provides relief. It takes a conscious effort to meet the fiber goal of 25-38 grams per day without a strategic effort.

If you feel that you all already hitting or exceeding your fiber goal and you are still experiencing gas and bloating, you may also be experiencing back up bloating  due to inadequate elimination.

Back up bloating can occur in those with slow gut transit time and constipation, due to a build up of stool and gas. It is important to ensure you have an effective bowel regimen in place to allow for adequate laxation when fiber intake is high, this may require modifications such as postural changes when toileting (check out the squatty potty), the addition of osmotic laxatives, and/or magnesium salts.

I want to link you to this article from FODMAP Everyday® Success Team Contributor Tamara Duker Freuman MS, RD, CDN who does a wonderful job explaining this scenario.

IBS-D & Fiber

Many of my IBS- D patients think fiber is bad since it is associated with more frequent bowels. It is important to remember that fiber (specifically soluble) can act as a bulking agent AND can help bind stools, working magic for those suffering from diarrhea.

Yes, fiber can add bulk to bowels, however it can also hold stool together and form a viscous gel helping to minimize diarrhea episodes. It often takes a little experimenting to find the right combination or foods and fiber supplements. It is best to increase soluble fibers such as oats, beans, flaxseeds, chia seeds, and low FODMAP fruits and vegetables to boost this beneficial fiber.

Always remember to drink adequate water intake when increasing fiber intake since risk of constipation is more likely to occur if we are dehydrated, plus the extra fiber requires extra water for digestion.

Always remember to drink adequate water intake

Check out these high fiber, low FODMAP foods. Please use your Monash University app for exact low FODMAP serving sizes.

  • 1-ounce (30 g) pumpkin seeds = 5.2 grams fiber
  • 1 tablespoon Chia seeds = 4.1 grams fiber
  • 1 tablespoon Flax seeds = 2.9 grams fiber
  • 1 medium sweet potato baked in skin = 3.8 grams fiber
  • 1 medium baked potato in skin = 3.6 grams fiber
  • 3 cups (55 g) air popped popcorn = 3.5 grams fiber
  • 1 medium orange = 3.1 grams fiber
  • 1-ounce (30 g) nuts = ~3 grams fiber
  • ½ cup (78 g) cooked quinoa = 2.6 grams fiber
  • ½ cup (84 g) canned and drained chickpeas = 8.1 grams fiber
  • ½ cup (90 g) cooked black beans = 7.5 grams fiber
  • ½ cup (52 g) raw oats = 4 grams fiber
  • 1 cup (150 g) strawberries = 2.9 grams fiber
  • 1 cup (125 g) chopped carrot = 3.6 grams fiber
Here is an example of a low FODMAP, fiber rich day. This menu provides ~34 grams of fiber.

⅓ cup (34 g) dry oats cooked in water or lactose-free milk, 2 tablespoon walnuts pieces, 1 tablespoon chia seeds, and ¼ cup (40 g) fresh or frozen blueberries  .


3 cup (112 g) mixed low FODMAP greens (such as arugula, kale and lettuce), ¼ cup (42 g) canned and drained chickpeas, 1-2 tablespoon shredded cheese, 10 chopped almonds, and ⅓ cup (52 g) cooked quinoa, and low FODMAP salad dressing


Lundberg Brown Rice Cake + 1 small ripe banana + 1 tablespoon peanut butter


3-ounces (85 g) protein of choice (chicken, fish, beef, etc.), 12 green beans, 1 cup cooked carrots, and 1 cup (180 g) cooked brown rice.



Should I Be Taking a Fiber Supplement?

Remember this  is not a one size fits all situation. There are several fiber supplements that are appropriate for IBS. Please speak with your dietitian or health care provider to see if a fiber supplement is appropriate for you.

#1. Psyllium Husk Fiber

This fiber retains water and provides bulky, easy-to-pass soft stools. Psyllium has been shown to be more effective than stool softeners for those with chronic idiopathic constipation and is also touted as one of the “go to” fiber source for IBS. It has been shown to help normalize stools and reduce IBS symptoms .

As a dietitian I recommended pure psyllium husk powder mixed with a little cranberry juice, lactose-free milk, or low FODMAP milk alternative such almond, rice, or lactose-free milk. It thickens up quickly so be ready to drink soon after mixing. Metamucil is a psyllium-based product that comes in several flavors. I am less inclined, however, to recommend this brand due to the large amounts of added sugar.

#2. Partially Hydrogenated Guar Gum

Partially Hydrogenated Guar Gum (PHGG) is also known as Sunfiber. This is a water soluble, non-viscous fiber supplement. It has become a more popular fiber supplement in the FODMAP community and many PHGG fiber supplements are low FODMAP certified including Regular Girl, Nutrisource Fiber in addition to Sunfiber. This fiber supplement dissolves well in most liquids. Sunfiber is a prebiotic fiber that may help populate the gut microbiome, which may be negatively affected when one adapts a low FODMAP diet. Evidence supports PHGG in the management of both IBS-C and IBS-D.


Regular Girl Prebiotic Fiber Banner Ad

#3. Acacia Fiber

Acacia fiber, also known as acacia gum, is a soluble fiber that helps promote regularity. This fiber tends to mix well and does not thicken up like some fiber supplements making it a little easier to drink for some.

#4 Methylcellulose

Methylcellulose is found in Citrucel and MiraFiber is a non-fermentable fiber source, which is suitable for those with IBS. Both the powder or capsules are effective, however be sure to read the directions for proper dosing.

#5 Calcium Polycarbofill

Calcium Polycarbofill is found in FiberCon, is low FODMAP, and can be effective for either IBS-C or IBS-D.

#6. Wheat Dextrin

Wheat dextrin, also know as Benefiber, is a soluble fiber and not well studied with IBS patients, however, clinically it appears to be well tolerated. Discuss the possibility of trying this with your dietitian.

Fiber Supplements To Avoid

#1. Inulin

Inulin based fiber supplements should be avoided when following the low FODMAP diet. Take a look at this gummy bear fiber supplement I saw at the pharmacy recently (ingredients below)! This would NOT be a good choice since the first ingredient is inulin, a high FODMAP ingredient.

Ingredients: Inulin (a natural vegetable fiber) Sugar, Pectin, Citric Acid. Sodium Citrate, Natural Flavors (Blue Raspberry, Cherry, Pear), Natural Colors (Black Carrot, Annatto, Genipap Juice Concentrate, Watermelon Juice Concentrate), Vegetable Oil, Carnauba Wax

#2. Wheat Bran

Wheat bran is a high FODMAP ingredient and is not a suitable fiber choice.

#3. Polydextrose

You might come across polydextrose-based fiber supplements. These have not been well studied in relation to IBS and can flare IBS symptoms for some.

Ingredients To Avoid

As always, read the label!

Avoid the following ingredients:

  • Xylitol
  • Sorbitol
  • Malitol
  • Lactitol

These are all sugar alcohols which fall under the polyol group, which are high FODMAP. Watch out for supplements that are labeled sugar-free since this can be a sign that they contain sugar alcohols.

  • FOS or fructooligosaccharides
  • Fructose (glucose-fructose syrup is okay; fructose-glucose syrup is not)
  • High Fructose Corn Syrup (regular corn syrup is fine)
  • Agave or honey in excessive amounts (Monash has lab tested these sweeteners and 1 teaspoon is low FODMAP but it is very difficult to tell how much is included in a prepared food or supplement).

Testing What Works For You: One Fiber Might Work When Another Doesn’t

Many of us have “trialed” a fiber supplement at one time.

If you were not happy with the results, it is worth trying a different fiber supplement, since they behave differently and you may find one that works better.

For those who had a bad outcome with a particular fiber, avoid this fiber source and try one of these other gut-friendly fiber sources discussed in this article. Always start off small and increase as needed. Be sure to look at the serving size since these vary brand to brand. Powders often contain more fiber than capsules.

While there is not a perfect time to take a fiber supplement, I often encouraged my patients to take them when they are most likely to remember. Personally, I prefer the evening time and have seen better results with this time window. For those who are afraid of bloating, an evening trial may be less nerve wrecking than earlier in the day.

An alarm clock with the text:While there is not a perfect time to take a fiber supplement, I often encouraged my patients to take them when they are most likely to remember.

I hope this helps shed light on the importance of fiber and what fibers to reach for. Please consult your Registered Dietitian and health professional if you have a digestive disorder that may require a modified fiber diet such as gastroparesis, IBD, or diverticular disease for specialized recommendations based on your individual needs.

Fiber Supplement Brands

These Fiber Supplements are Certified Low FODMAP

All of these certified supplements are made with Partially Hydrogenated Guar Gum
This low FODMAP certified fiber supplement is made from resistant starch.
Other low FODMAP certified fiber product:

Want to order Good Mix Superfoods Blend 11 in Australia? Then ORDER HERE.

Check out their Instagram page for endless inspiration for how to integrate Blend 11 into your daily meal plan!

Products Using Low FODMAP Certified Ingredients
These Fibers Supplements are NOT certified low FODMAP, however are suitable options for IBS.
Acacia Fiber Supplements:
Psyllium Fiber Supplements:
Methylcellulose Fiber Supplements
Calcium Polycarbofill Fiber Supplements
Please make sure you work with your Registered Dietitian to determine which fiber supplement is right for you.

Looking to share this information with your clients or a loved one? Download this article as an ebook for 99 cents. 

FIber and IBS ebook cover

You might also enjoy reading our interview with Dr. B about his book, Fiber Fueled, which addresses fiber, plant-based eating and the low FODMAP diet.


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