Soluble Fiber vs Insoluble Fiber on Keto

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Written by Rahul Malpe, Certified Nutritionist and medically reviewed by Abby Courtenay

Imge of Soluble Fiber vs Insoluble Fiber on Keto



Fiber is a hot topic on keto. Should you be eating soluble or insoluble? What is the difference? And does it really matter? 

In this article, we’re going to break it all down for you and help you decide which type of fiber is best for your keto diet. Let’s get started.


What is fiber?

It is a type of carbohydrate that the body cannot digest. Though we don't digest fiber, it's a very important part of a healthy diet. It is found in plant foods like fruits, vegetables, whole grains, and beans. 

There are 2 types: soluble and insoluble. 

  • The soluble type dissolves in water and helps to regulate the body's digestion. 
  • The insoluble type doesn't dissolve in water and helps to add bulk to stool, making it easier to pass through the digestive system.

Both types are important for maintaining a healthy digestive system. It has also been linked to a number of health benefits, which we will discuss in the upcoming sections.


What is soluble fiber for keto?

As the name suggests, it is a type of dietary roughage that dissolves in water to form a gel-like substance. It is found in many plant-based foods, including oats, legumes, nuts, seeds, psyllium, and some fruits and vegetables. 

When we eat foods that contain this nutrient, it travels undigested through the stomach and small intestine until it reaches the large intestine. In the large intestine, it is fermented by bacteria. This fermentation process breaks down the fibers into short-chain fatty acids, which are absorbed into the bloodstream and used for energy. 

Additionally, it helps to keep the large intestine healthy by promoting regularity and preventing constipation. It does this by attracting water and forming a soft, bulky stool that is easy to pass.

Aside from that, by binding with bile acids, it plays a role in cholesterol management by lowering LDL (“bad”) cholesterol levels. Thus, it is a critical component of a healthy diet for these reasons.


What is insoluble fiber for keto?

This type of dietary roughage doesn't dissolve in water. It goes by many names, including roughage, non-starch polysaccharides (NSPs), and resistant starch. 

While the body cannot digest or absorb it, it’s important because it helps to add bulk to the fecal matter and keeps the digestive system working properly.

It is mostly found in plant foods, such as wheat bran, whole grains, and vegetables. When these foods are eaten, it passes through the gastrointestinal tract largely intact. As it moves through the gut, it absorbs water and increases the bulk of the stool. 

This helps to keep the digestive system regular and prevents constipation. Additionally, it may help to reduce the risk of diverticular disease and hemorrhoids.

What are the benefits of each type of fiber?

Benefits of soluble fiber for keto

It has a number of benefits for the body, both when consumed as part of a healthy diet and when used as a dietary supplement. 

  • It helps to regulate blood sugar levels by slowing down the absorption of glucose into the bloodstream.
  • It promotes regularity by helping to add bulk to the stool and keeping the intestine clean. 
  • It has been shown to lower cholesterol levels by binding with bile acids and promoting their excretion. 
  • It is a prebiotic, which means it helps to promote the growth of healthy bacteria in the gut.

Benefits of insoluble fiber for keto

Consuming a diet that is rich in insoluble roughage offers many benefits. 

Fibers of this nature have been proven to be effective in providing bulk to your stool. Due to this reason, they are excellent natural laxatives

You may even find laxatives that are made from extracts from plant sources of insoluble fiber, which are actually processed into laxatives. By regularly eating foods that are rich in them, you can also reduce your chances of developing constipation as these foods promote bowel movements. 

Aside from that, it also has another benefit in that it facilitates the passage of other foods through the digestive tract at a much faster rate than they normally would.

In addition, it helps to clear toxins and excess cholesterol from the body, reducing the risk of heart disease and other chronic conditions. 


What are the risks of each type of fiber?

Soluble fiber risks

Excess consumption of it can lead to gastrointestinal issues like bloating, gas, and diarrhea. If you eat too much of it at once, it can also cause indigestion and abdominal pain. 

Insoluble fiber risks

For one thing, too much of it (without adequate fluid intake) can promote gastrointestinal issues like constipation. This is because it can add bulk to the stool and make it more difficult to pass through the digestive system. 

Bloating can also happen if you eat a large amount of roughage in a short amount of time, especially if you are not used to eating this much. Fiber isn't digested by the human body, so it’s still intact when it reaches the large intestine. However, bacteria living in the large intestine do digest some of the roughage and produce gas as a result.

Lastly, excessive intake of it can increase the risk of irritating the gut, which could lead to diarrhea.  While there are some risks associated with eating too much insoluble fiber, it's still a healthy part of the diet. Just be sure to eat it in moderation and drink plenty of water to reduce the chances of gastrointestinal issues.


What are the recommendations for fiber on keto?

The recommended amount of fiber for keto or any diet is 14 g per 1,000 calories consumed, which can equate to 25 - 34 g depending on your gender, age, and the number of calories you should eat each day.

As you may know, a key component of the ketogenic diet is reducing carbohydrate intake, which can lead to reduced fibrous food intake as well. This is because many high-fibrous foods are also high in carbohydrates, such as oats and legumes. 

However, it is still possible to meet your daily requirements on a ketogenic diet. There are a variety of low-carbohydrate, high-fibrous foods that can be incorporated into the diet, such as artichokes, leafy greens, avocados, Brussels sprouts, chia seeds, and raspberries. 

In addition, there are a number of supplements available that can help increase roughage intake. For example, psyllium husk is a type of soluble fiber that can be taken in powder form. 

By including these foods and supplements in your diet, you can make sure you are getting the roughage you need while still following a ketogenic diet.


Bottom line about fiber for keto

So, what’s the verdict? Is soluble or insoluble fiber better on keto? The answer is both!

The soluble type can help you feel fuller longer and keep your blood sugar stable, while the insoluble type helps with regularity and keeping things moving through your digestive system.

In order to follow a healthy keto diet, aim to include a balanced mix of both types of roughage in your diet.