The Difference Between Soluble and Insoluble Fibers and Their Roles In IBS

Fiber is vital for IBS management and gut health, but not all fiber is actually the same. Fibers can either be labeled as soluble and insoluble. Let’s break each type down, then talk about which one may be best for your IBS symptoms.

Soluble Fiber

Soluble fiber dissolves in water. As it moves through the digestive tract, it dissolves water and forms gel. This helps to speed up digestion by softening the stool, and can help boost beneficial gut bacteria!

Source: oats, beans, lentils, many fruits and vegetables, chia seeds, flax seed, psyllium husk, avocado, and oat bran.

Insoluble Fiber

Insoluble water doesn’t dissolve in water. As it moves through the digestive tract, it doesn’t break down or change. Instead, it adds bulk to the stool and helps stool move more quickly through the digestive tract.

Sources: the skin and stalks of many fruits and vegetables, cauliflower, potatoes, wheat bran, nuts, beans, peas, and lentils.

Fiber and IBS

Fiber supports overall digestion, and helps boost good bacteria in the gut. For those with IBS, fiber can help regulate bowel movements, which could help alleviate symptoms. Studies have shown more success in IBS symptom relief with soluble fiber, especially supplemental psyllium. Too much fiber could also trigger symptoms, especially if increased too quickly. Recommended daily fiber intake is 20-30 grams for women and 30-40 grams for men. If you’re going above that, it may be helpful to reduce insoluble fiber, until symptoms improve.

It’s best to work with your dietitian to determine which sources of fiber may be best for you, especially if you are working through a low FODMAP diet. A simple way to start incorporating more fiber into your diet is to start with small portions of soluble fiber at a time from whole foods sources. Your dietitian can help you go from there, or consider whether or not supplemental fiber would be beneficial.