What's the Difference Between Insoluble and Soluble Fiber, According to a Dietitian

In This ArticleView AllIn This ArticleWhat Is Soluble Fiber?What Is Insoluble Fiber?How Much Fiber Should You Eat Every Day?

In This ArticleView All

View All

In This Article

What Is Soluble Fiber?

What Is Insoluble Fiber?

How Much Fiber Should You Eat Every Day?

Fiber is one of those do-it-all nutrients that most of us aren’t getting enough of. Over 90% of adults in the United States do not eat enough fiber each day, despite its health benefits, according to the2020-2025 Dietary Guidelines for Americans.

Present mainly in plants—vegetables, fruits, whole grains, legumes, nuts and seeds—fiber is a type of carbohydrate that’s primarily undigested and passes through the digestive tract. Fiber comes in two forms: soluble and insoluble, which both provide distinct benefits.

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Most plant-based foods come with both types of fiber in varying amounts. Research like a 2022 review inFood Science and Human Wellnessshows that together, soluble and insoluble fiber form a mighty team to support a healthy gut and reduce the risk of chronic conditions, such as diabetes, heart disease and some types of cancers. Bulking up your diet with fiber has also beenfound to support weight loss.

If you want to increase your fiber intake, read on to learn about the differences between soluble and insoluble fiber and what foods contain each type of fiber. (Hint: Don’t peel your apples.)

According to the National Library of Medicine’s resourceMedlinePlus, soluble fiber is a type of fiber that absorbs water, forming a gel in the digestive tract and making stools easier to pass.

Benefits of Soluble Fiber

Because of its ability to absorb water and swell up, soluble fiber helps slow down the digestion of carbohydrates—and other nutrients—preventing sudden spikes in blood glucose levels. This slower digestion also helps keep you feeling fuller longer, which is especially helpful when it comes toweight loss.

And that’s not all. A 2023 review inNutrition Journalsuggests that eating soluble fiber might lower blood pressure. This may be in part because eating foods with this fiber improves satiety, which can lead to weight loss and lower blood pressure, but further research is needed to pinpoint the reason why.

What Foods Have Soluble Fiber?

You can find soluble fiber in a wide range of plant-based foods, such as:

Contrary to soluble fiber, insoluble fiber is just what it sounds like—a type of fiber that does not absorb water. Rather than forming a gel-like soluble fiber, insoluble fiber adds bulk to the stool and draws water to the colon, making stools soft and easy to pass.

Benefits of Insoluble Fiber

Becauseinsoluble fiber bulks up the stooland makes it softer and easier to pass, it limits the amount of time the stool is sitting in the colon. This means that any chemicals in the foods you’re eating won’t be sitting around as long, which reduces the chances of them causing harm. This may lower the risk of colorectal cancer.

Combined with soluble fiber, insoluble fiber may reduce your risk of type 2 diabetes, per a 2020 study in theJournal of Diabetes Investigation.

And a 2023 review inNutrientssuggests that the benefits of insoluble fiber may go beyond just the fiber itself and its effects on bulking up the stool. Scientists looked deeper at the evidence and found that the powerful plant compounds in fiber may be important contributors to disease prevention and improved health in addition to the fiber itself.

What Foods Have Insoluble Fiber?

Insoluble fiber is the tough and chewy parts of vegetables and fruits, such as apple skins, carrot peels, broccoli stems and asparagus stalks. In addition to being found in produce, you can also find insoluble fiber in whole-grain breads and cereals, wheat bran, oat bran andnuts.

There are no specific recommendations on the amount of each type of fiber you should eat each day. The2020-2025 Dietary Guidelines for Americansrecommends daily fiber intake based on age and gender. If you are pregnant, your fiber needs also change.

Generally speaking, aiming for 25 grams a day is a great goal and 30 grams or more is even better.

Women:

Pregnant Women:

Men:

Enjoying a range of fiber-rich foods ensures you consume both types of fiber. Instead of meticulously tracking fiber intake, pay attention to the signs thatyou might be getting too muchortoo little fiber—both of which can cause gas, bloating and abdominal cramps. Eating too little fiber can alsocause constipationand consequently hemorrhoids due to difficulty in passing stools.

12 Foods with More Fiber Than an Apple

The Bottom Line

In short, soluble fiber forms a gel and acts as a sponge to help sweep fat and cholesterol out of your intestinal tract, while insoluble fiber bulks up your stools. Both types of fiber are essential for supporting a healthy digestive system and overall wellness. If you’reincreasing your fiber intake, take it easy and progressively increase the amount over time. It’s also important to increase your intake of fluids, such as plain water, to support healthy digestion and help pass the stool out of the body.

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