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Soluble vs. Insoluble Fiber: What's the Difference?

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  • Soluble and insoluble fiber are beneficial to your diet and can help support gut health, heart health, lower your risk of diabetes and help with weight management.
  • Soluble fiber helps to create a gel, which works to form and soften stool. This can help in prevention in both constipation and diarrhea.
  • Insoluble fiber works as a mechanical irritant and structural base for stool​. This acts as the bulk of the stool, and can help to pull the water into the GI tract. Increasing insoluble fiber is increasingly recommended to those inflicted with constipation. 
  • A healthy combination can help in preventing both constipation and diarrhea.

Whether you suffer from digestive troubles or are just trying to bolster your overall health, you can benefit from eating more fiber. Also, known as roughage, fiber is the part of plant-based foods that the body doesn’t entirely break down. Think: the skin of fruits and veggies or the rough, stringy part of a stalk of celery. Though the body might not break it down entirely, it’s still a super-beneficial and crucial nutrient that can help improve digestive health and general wellness.

Why Fiber Matters

Fiber is a part of a low-FODMAP diet plan and can help balance out your digestive health if you suffer from irritable bowel syndrome (IBS) or routinely experience diarrhea, constipation or bloating.

What is FODMAP? Read our in-depth guide to the low-FODMAP lifestyle for more information on this highly effective diet for digestive health.

Though, there’s a lot more to fiber than just its ability to keep you “regular”. Fiber is also good for your heart, as it helps keep cholesterol levels in check by lowering low-density lipoprotein (otherwise known as bad cholesterol) and reduces blood pressure and inflammation. Researchers also believe that eating ample fiber can help control blood sugar levels and aid in maintaining a healthy weight.

But there are two different kinds of fiber that you need to know about: soluble and insoluble. Both are essential to a healthy diet and have strengths that make them a fantastic weapon in your wellness toolkit. Read this guide to learn more about the different types and how they’re both employed for good health.

Soluble Fiber: Good for Diarrhea and Constipation

Soluble fiber dissolves in water (to form a gel), which means it can slow down digestion (great for people with diarrhea) and soften hard stool (great for people with constipation). It’s found in potatoes, yams, Brussels sprouts, oatmeal, flaxseed, nuts, beans, apples and blueberries.

oatmeal with bananas blueberries

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Soluble fiber does it all — softens stool and firms it up, making it amazing for pretty much every diet. Soluble fiber’s most powerful characteristic is its ability to attract and absorb water, which brings benefits for those who suffer from diarrhea and constipation. As soluble fiber travels through your system, it pulls  food together, turning it into a softer substance that’s easier for the body to digest.

  • Diarrhea — If you have diarrhea, soluble fiber can absorb extra liquid and firm up stool, effectively slowing down digestion and preventing diarrhea. When the food in your intestines is mostly liquid, the muscles in the bowels don’t have anything to grip on to, so the food passes through the digestive tract too quickly, causing diarrhea, bloating and discomfort. Soluble fiber can help improve grip and keep digestion moving more smoothly.
  • Constipation — Since it’s so good at absorbing water, soluble fiber is also used to soften stool so it moves through the intestines more quickly. This means it’s incredibly helpful for those who experience constipation and tough bowel movements.

To put it simply, soluble fiber is essential to every body and every diet!

Insoluble Fiber: Good for Constipation

Insoluble fiber doesn’t absorb water but adds bulk to stool, which can speed up digestion and help food move through the digestive tract more quickly. For this reason, insoluble fiber is generally only recommended for people with constipation. It’s found in whole grain foods, wheat bran, lentils, cereal, leafy vegetables, legumes, celery, zucchini and the skins of root vegetables. 

fresh salad bowl
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Unlike soluble fiber, insoluble fiber is made of plant pectin and gums that add bulk to your diet and help food move through the intestines quickly. Insoluble fiber doesn’t dissolve in water, but it instead attracts water, which makes stool softer and prevents strain. This is great for those who experience constipation and pain when going to the bathroom, but not so great for those who struggle with diarrhea. Insoluble fiber triggers a powerful gastrocolic reflex that can cause diarrhea, stomach cramps and discomfort, so it shouldn’t be eaten in excess by those sensitive to diarrhea.

Aim for a Balance of Both

In order to support your entire body — from the digestive tract to the heart and beyond — your diet should include the right balance of both soluble and insoluble fiber. Get the right amount of fiber easily by trying our low-FODMAP meal delivery plan that can revolutionize your health and well-being!