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What Are Soluble Fibers? (Everything You Need To Know)

Michael Garrico
Published by Michael Garrico
Fact checked by Donald Christman, BHSc FACT CHECKED
Last updated: June 1, 2022

Dietary fiber is the indigestible carbohydrate of plant-based food. Unlike fat, proteins, and carbohydrates, nutritional fibers pass untacked through our digestive system.

I had a brief period when I didn’t eat plant-based food at all and noticed my digestive health worsened considerably. Since then, I’ve been exploring and reading all I could find about soluble fiber.

Together with my team, I did more thorough research, reading hundreds of relevant articles to synthesize knowledge and compile everything into this article.

Let’s dive in.

Quick Summary

  • Soluble fiber is a dietary fiber that dissolves in water.
  • It can lead to lower cholesterol, improve heart health and weight loss, and even prevent metabolic syndrome.
  • Good sources of soluble fiber are legumes, fruits, vegetables, and whole grains.

What Is Actually Soluble Fiber?

A soluble Fiber mixed with water

Soluble fiber is actually a part of dietary fiber that dissolves in water.

They are also called prebiotic fiber or fermentable fiber, and essentially they are plant carbohydrates.

The soluble fiber is mainly made of pectins and plant gums, with the first being the building material for plant cell walls, and the second, the plant products formed mostly as a result of plant cellulose destruction.

The other components are beta-glucans, oligosaccharides, and wheat dextrin. In some specific foods, there are also inulin ( chicory root) and psyllium (plants in the genus Plantago).

While moving through the digestive tract, it attracts water and body fluids and turns into the consistency closest to one when you sip water into your oatmeal.

Differences Between Soluble and Insoluble Fiber

Insoluble fiber is inert to digestive enzymes and can’t be dissolved in water. Therefore they leave the bowel without breaking down.

Insoluble fiber is made chiefly of cellulose and lignin, which are specific carbohydrates found in plant cell walls, and they don’t provide the body with any calories.

It may support insulin sensitivity and aid bowel regularity, but both soluble and insoluble fiber compensate for each other, and both have their health benefits in terms of digestive health and the body in general.

Benefits of Soluble Fiber

Grabbing a soluble fiber to drink

Combined with fluids, soluble fiber dissolves in water and gives the stool a gel-like consistency.

Formed as a gel, it turns into good gut bacteria food, making it an essential part of the healthy gut flora.

While digesting, gut microbiota produces short-chain fatty acids, which may aid in fat metabolism [1].

It’s worth mentioning, as some studies suggest that short-chain fatty acids may also decrease the possibility of getting colon cancer [2].

Research shows that this type of fiber might also play a significant role in maintaining normal cholesterol levels and blood sugar [3].

Forming a specific structure and reaching the intestines intact, this fiber creates a feeling of fullness for more extended periods. Those periods will help you eat fewer calories and maintain a healthy weight.

“The whole role of it is to aid in slowing down the digestion, so everything passes through the intestines a lot slower and it promotes good GI health.” - Lisa Burnett, registered dietitian

Absorbing water on its way to the colon, this type of fiber builds up softer and bulkier stool. This specific stool type leads to regular bowel movements - reducing constipation and diarrhea [4].

Related Articles: Does Soluble Fiber Help You Lose Belly Fat?

Good Sources of Soluble Fiber

To help you consume more soluble fiber in your diet, aim to pick a few of the following high fiber foods.

1 - Legumes

The top of the list is reserved for legumes - beans, lentils, and peas.

One cup of black beans contains 15 grams of soluble fiber, especially pectin. Lima beans have almost identical percentages of soluble fiber, and so do kidney beans, green beans, etc.

2 - Fruits

Fruits rich in soluble fiber are avocados, pears, figs, nectarines, apricots, and apples. Keep in mind that eating fresh fruits will also provide you with numerous vitamins and minerals.

3 - Vegetables

Brussel sprouts, sweet potatoes, broccoli, turnips, and carrots are the best vegetable options high in soluble fiber.

4 - Grain

If you are a pastry lover, try to avoid white flour (which contains a minimum percentage of fiber). Good sources of soluble fiber among grains are oats and barley.

Other sources worth mentioning are hazelnuts, chia, flax seeds, and sunflower seeds.

How to Get Enough Dietary Fiber

A healthy fruits and vegetables snack

Here are some tips on how to maintain a high fiber diet and reap the health benefits:

  • Take whole-grain cereals for breakfast (oat bran)
  • Choose healthy snacks such as dried fruits, fresh fruits, nuts, popcorns, and raw vegetables
  • When possible, consume fruits and vegetables without peeling them
  • Eating whole fruits and vegetables over making a juice
  • Increase legumes consumption
  • Choose foods with higher fiber content -  “whole grain,” “fiber,” “bran” label
  • Switch to whole wheat flour (wheat bran)
  • Use products with added fiber (containing chicory root or inulin)
  • If necessary, use fiber supplements (Psyllium, Metamucil, Fibercon, Citrucel)

How Much Fiber Is Enough?

How much soluble and insoluble fiber is enough depends on age and sex. Dietary fiber is vital for overall health, but too much fiber may cause some issues with bloating, cramps, and gasses. So take everything in moderation.

According to the Institute of Medicine, there is a daily fiber intake recommendation for adults [5]:

  • Men aged 50 or younger: 38 grams
  • Men aged 51 or older: 30 grams
  • Women aged 50 or younger: 25 grams
  • Women aged 51 or older: 21 grams

The vast majority of Americans don’t consume nearly enough fibers in their diet, so be sure to increase soluble and insoluble fiber intake gradually [6].

And keep in mind to drink plenty of water because dietary fiber works best with the abundance of fluids.

FAQs

Is Rice a Soluble Fiber?

Yes, rice is a soluble fiber. It contains a moderate level of soluble fiber. About 100 grams of rice has 0.4 grams of fiber.

Are Bananas High in Soluble Fiber?

No, Bananas are not high in soluble fiber. Other fruits may be a better source, considering one banana contains only 0.3 grams of soluble fiber.

Is Soluble Fiber Good for Diarrhea?

Soluble fiber may be good for diarrhea. Soluble fiber absorbs extra water in the stool, decreasing the bowel-movement frequency.

Should You Increase Soluble Fiber Intake?

A healthy diet rich in dietary fiber should reduce the risk of various health conditions like high cholesterol, blood sugar, and poor gut health.

If you aren’t a fan of plant-based foods, you could take dietary fiber supplements or try to use something like Psyllium as a thickener instead of white flour or cornstarch.

If you want to improve your digestive health even further, I'd recommend opting for some of the best collagen supplements on the market.

Nothing is a substitute for real food, but these supplements can help move the needle when we're too busy to eat right.


References:

  1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3735932/
  2. https://pubmed.ncbi.nlm.nih.gov/12468628/
  3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3399949/
  4. https://www.oncologynutrition.org/erfc/eating-well-when-unwell/chemotherapy/constipation-diarrhea-and-fiber
  5. https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/high-fiber-foods/art-20050948
  6. https://www.health.harvard.edu/blog/should-i-be-eating-more-fiber-2019022115927

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