How Much Fiber Do You Need With IBS?

Irritable Bowel Syndrome (IBS) is one of the most common digestive issues affecting people today. Those suffering from this condition are often advised by their doctors to add more fiber to their diet. But is this the best recommendation for everyone with IBS?

When I was first diagnosed with IBS (before I became a nutritionist), I was eating a high-fiber, mostly vegetarian diet.  I was eating lots of beans, onions, garlic, lentils, guacamole and whole grains.  What I didn’t know at the time was that my diet was making me feel horrible.  Now I know why. 

Let’s take a look at the role fiber can play with digestive health and why adding more fiber to your diet may make you feel worse. 

Current Dietary Guidelines – Fiber

The USDA recommendation for daily intake of fiber is:

  • Adult men – 34 grams
  • Adult women – 28 grams

The problem is that everyone’s needs are different.  Some need more, while others need less. This is especially true as we age and may require less fiber intake.  And when you are experiencing digestive issues, then the typical recommendations might not always apply.

What Exactly Does Fiber Do?

As you may know, fiber is beneficial to overall health as it can:

  • Lower cholesterol
  • Help us feel full and stabilize blood sugar levels.  Stable blood sugar levels means steady energy, less fatigue, less inflammation, less anxiety and keeps that pesky “hangry” feeling at bay. 
  • Help prevent some conditions such as Type 2 diabetes, colon cancer and cardiovascular disease

Fiber also plays an important role in our digestive health:

  • It helps keep our colon cells healthy and happy.  The good gut bacteria in our colon ferments fiber.   The by-products of this fermentation process helps nourish the colon cells, which then contributes to overall improved gut health.
  • The fiber fermentation process also helps to keep the colonic pH acidic, which can help prevent the colonization of pathogenic bacteria, which can cause illness (yeah, that’s the last thing we need)
  • It assists in forming regular and soft bowel movements which can prevent constipation

Yay for fiber! 

Types of Fiber and What They Do

There are two types of fiber found in plant-based foods, insoluble and soluble fiber.

  • Soluble fiber dissolves in water, creating a gel-like substance, which aids in making bowel movements soft and smooth.
  • Insoluble fiber does not dissolve in water, which means it is left intact and helps to create bulk to the stool.  It also helps stimulate movement through the digestive tract. 
  • Whole plant-based food contains both soluble and insoluble fiber, but some contain more of one than the other.
  • Foods high in soluble fiber include oats, barley, peas, beans and lentils, nuts, seeds, apples, citrus fruits and Psyllium, a fiber supplement.
  • Foods high in insoluble fiber include; whole wheat flour, wheat bran, beans, nuts, green beans, root vegetables such as potatoes, and vegetables in the cabbage family such as cauliflower.
  • Keep in mind, foods that are higher in insoluble fiber are more likely to cause bloating and abdominal pain

Fiber & IBS

Show of hands…For those of you diagnosed with IBS, did your doctor recommend that you take a fiber supplement? Did it help?

If it didn’t help or if you felt worse, then this may be why:

  • Remember, our good gut bacteria ferment fiber.  And a by-product of fiber fermentation is gas, which can cause discomfort, bloating, cramps, and abdominal distension.
  • You may have SIBO, which is an overgrowth of bacteria in the small intestine, where it doesn’t normally belong in large numbers. The bacteria in the small intestine ferments the fiber causing digestive distress.

Can a Low-Fiber Diet Help IBS?

  • One study found that a low-fiber diet helped those mostly with IBS-M for Mixed (alternating constipation and diarrhea) and IBS-D (diarrhea). This diet normalized bowel movements and improved gas, bloating, urgency, and abdominal pain.
  • Another study showed that for those with IBS-C or chronic constipation, adding fiber to the diet can cause bloating, gas, and abdominal distension. When fiber was eliminated for a short time and then gradually reintroduced to a personalized level, symptoms improved (1).

Low-Fiber Diets

So is a low-fiber diet right for you and if so, one?  It will depend on your condition and the severity of your symptoms. As always, the amount of fiber within these diets needs to be personalized.


  • One of the most studied diets for IBS and is used for other digestive conditions such as IBD (Inflammatory Bowel Disease) and SIBO
  • A Low-FODMAP diet reduces the amount of fermentable carbohydrate intake, which means less fermentation by gut bacteria, less water in the intestines and less opportunity for gas, stomach distension, diarrhea and constipation, leading the way for a happy belly.

SIBO Diets

  • SIBO-Specific Diet was developed by Dr. Alison Siebecker. This is a combination of the Specific Carbohydrate Diet and Low-FODMAP Diet. It is also the most restrictive of all the diets and usually recommended only when the others aren’t providing enough relief.
  • SIBO Bi-Phasic Diet is a 3-month protocol developed by Dr. Narala Jacobi. It is a variation of the SIBO-Specific diet in that it is implemented in phases which can feel less restrictive to some people.
  • Fast Tract Diet was developed by Dr. Norm Robillard and is similar to the Low-FODMAP diet as it restricts fermentable carbohydrates however, it uses a different mathematical formula by focusing on restricting the total amount of fermentable carbohydrates. Users can track their fermentable points in order to stay in a range (similar to using Weight Watchers points) depending on severity of symptoms. This may be useful for those who need more structure than the low-FODMAP but less restriction of the other diets.

Paleo Diet

  • This diet consists of eating foods that were supposedly available to humans during the Paleolithic era
  • It typically includes lean meats, fish, fruits, vegetables, nuts and seeds and restricts grains, legumes, dairy, sugar, processed foods, and alcohol.
  • By eliminating grains and legumes, it may be a naturally low-fiber diet 

Keep in mind that gut-healing diets are NOT forever diets.  They are meant to reduce symptoms, give your digestive system a much-needed break and help identify triggers to your symptoms. 

With that being said, sometimes less is more, which can be the case with fiber. Reducing fiber from the diet may help in the short-term, but as the gut heals, it’s important to determine how much fiber is beneficial and tolerable to add back in. This can be done over time, on a personal basis ,with what works best for you and your digestive tract.

As noted above, fiber plays a crucial role in our gut health and ultimately I want my clients on as much fiber as they can tolerate with the fewest symptoms.


1. Vanhauwaert, E., Matthys, C., Verdonck, L., & De Preter, V. (2015). Low-residue and low-fiber diets in gastrointestinal disease management. Advances in Nutrition (Bethesda, Md.), 6(6), 820–827.

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