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  • Ashley Sauvé Health

Soluble vs. Insoluble Fiber for Gut Health


Fiber is the part of plant foods that is non-digestible by our bodies; the part of our plant food that’s unable to be broken down during the digestive process.

Although it can’t be broken down into things like amino acids, fatty acids, or sugars that our bodies can use for various jobs, fiber is still really important for our health!

Fiber has many benefits:

  • Certain fibers help to bulk our stool, making it easy for our body to evacuate

  • Feeds the microbes that live in the gut, to keep them healthy, happy, and able to continue to work symbiotically with our bodies to keep us well

  • Reduces cholesterol levels in the body (especially LDL cholesterol)

  • Slows the digestive process, helping manage blood sugar levels, and insulin sensitivity

  • May reduce the risk for certain cancers

We know from studying traditional hunter-gatherer communities like the Hadza’s in Tanzania, that the amount and the types of fiber that we consume, plays a huge role in the microbial populations in the gut (studies show that their microbial populations in the gut have a greater variety). These communities eat upwards of 100-150g of fiber per day (much more than we eat over here in the western world)!

While 100-150g of fiber per day may be a lot for most of us (and not necessary) I tend to recommend at least 40-50g of fiber per day, and to aim for at least 6 cups of vegetables, and fruit per day, ensuring you get a variety! This is more fibre than the minimum recommended by Health Canada but there is plenty of research indicating that more fibre = more benefits.


What is Soluble Fiber

Soluble fiber is a specific type of fiber that dissolves (or is soluble) in water. In the gut, soluble fiber forms a gel-like substance.

This fiber can be helpful in both cases of diarrhea and constipation. In diarrhea, soluble fiber helps to slow transit time, by absorbing water from the intestinal tract. In constipation, these soluble fibers can help to soften stool, making it easier to pass.

This soluble fiber can act as a food source for the beneficial bacteria that live in our gut microbiome. We want to make sure these microbes are well-fed, so they can continue to provide us with health benefits!

Because soluble fibers can help to slow the digestive process, it can help manage healthier blood sugar levels. When our digestion slows, the release of glucose into the bloodstream slows, reducing significant blood sugar spikes that could otherwise occur without the fiber. Balanced blood sugar is important for stable energy, balanced hormones, and even good digestive function!

Here are some common sources of soluble fiber:

  • oats, oat bran

  • nuts

  • beans and legumes

  • flax seed

  • psyllium husk

  • berries

  • apples

  • carrots

  • avocado

  • barley


What is Insoluble Fiber


Insoluble fiber, on the other hand, is a type of fiber that does not dissolve in water, therefore not creating a gel-like substance in the gut, like with soluble fibers.

It adds more “roughage” to stool, making it bulkier, and attracts more water into the bowel, making stool easier to pass, thus keeping things regular! 💩 Because this type of fiber helps to keep things moving, it can help prevent things like hemorrhoids and diverticulosis from developing.

Here are some common sources of insoluble fiber:

  • fruits

  • vegetables

  • whole grains

  • beans and legumes

  • nuts


Supplementing with Fiber


Ideally, we want to be getting a variety of both soluble and insoluble fibers through a diversity of plant foods on a daily basis. The more you can consume a variety of foods that contain both these fibers, the better!

That being said, there can be a time and place where supplementing with fiber can be helpful to manage symptoms, or as part of a gut-healing protocol (your practitioner will know whether this might be a good option for you!).

Here are some of my favourite fiber supplements:

  • PHGG Partially-hydrolyzed guar gum is a type of soluble fiber that can be helpful in cases of IBS, and can help feed microbes in the gut. This type of fiber seems to be better tolerated for people who struggle with things like SIBO, or other imbalances in the gut microbiome.

  • Psyllium Husk You can find psyllium at health food stores, and even in most grocers! It can be found loose (which can be mixed into a liquid like water or juice), or encapsulated in pill form. Psyllium can be harsh on the digestive system, so go low and slow with this one, and ensure you’re drinking lots of water as you increase your fiber intake.



Note: always check with your trusted health care provider prior to taking any form of supplementation.




By now you’ve learned why fiber is important not only for good poops, but also for our gut microbiome, blood sugar balance, and more.

While yes, it’s an important part of our nutrition — it’s not the only way to support good digestion!

To learn more about how to support good gut health, check out my “Beginners Guide to Gut Healing”



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