By: Alison Embrey, CPT, PostGlo Intern

Did you know that fewer than 1 in 10 adults reach their daily recommendation for fiber intake?(1) With this in mind, taking the time to understand the importance of fiber and how to easily increase your intake of it, should be a no-brainer. Fiber comes from different kinds of plant-based foods, and is processed through your system without being digested. Fiber comes in two different forms; soluble and insoluble.(2) If you have ever tried avocado toast you consumed both insoluble and soluble fiber at the same time! Understanding the difference between soluble and insoluble fiber helps give a better understanding of how fiber supports your digestive health and overall well-being.

Fiber: The Basics

Dietary fiber is an essential type of carbohydrate that your body needs on a day-to-day basis. The primary function of fiber is to keep your digestive system working properly. Fiber is able to increase the weight and size of the stool in your body and soften it. Typically bulky stool passes through easier, and will reduce the risk of developing constipation.

Fiber provides many more benefits besides just aiding digestion. Fiber may lower cholesterol, improve blood sugar, and lower your risk for certain diseases such as Type II diabetes, heart disease, and colorectal cancer.(3)

Fiber also keeps your body fuller for longer, which is ideal for healthy weight management. This satiety effect is due to the combination of soluble fiber limiting your body’s ability to absorb fat, while insoluble fiber aids in more efficient water processing. There you have it, the secret to a perfect balance of fiber; insoluble and soluble fiber.

What is Soluble Fiber and How Does it Work?

Soluble fiber is a type of dietary fiber that dissolves in water to form a gel-like substance in the digestive tract, where it plays a key role in supporting heart and metabolic health. One of its primary functions is binding to cholesterol and bile acids in the intestines, which helps prevent LDL (“bad”) cholesterol from being absorbed into the bloodstream.(2) As a result, a diet high in soluble fiber—found in foods like oats, beans, apples, and citrus fruits—can significantly lower cholesterol levels and reduce the risk of heart disease. Additionally, soluble fiber slows the digestive process by delaying stomach emptying, allowing carbohydrates to be broken down and released into the bloodstream more gradually. This helps stabilize blood sugar levels and provides a steady source of energy. By also reducing fat absorption, soluble fiber contributes to overall better nutrient regulation and supports weight management. (2)

What is Insoluble Fiber and How Does it Work?

Insoluble is the other type of dietary fiber, but unlike soluble fiber it doesn’t dissolve in water and it remains largely unchanged as it moves down the digestive system. Insoluble fiber is made up of cell wall components like cellulose, hemicellulose, and lignin and is typically found in foods like whole grains, vegetables, nuts and seeds, and fruit skins.(6) Insoluble fiber works by passing through the digestive system largely intact, absorbing water and increasing stool bulk without dissolving. This added bulk stimulates the muscles of the intestinal wall, speeding up the movement of waste through the colon and promoting regular, efficient bowel movements. (2)

What’s the Difference between Resistant Starch and Fiber?

Now that you understand the basic differences between how soluble and insoluble fiber function, we can relate that to other aspects that affect our digestion. The topic of resistant starches has gained a lot of popularity recently, and it has been claimed that they may have many health benefits such as improved insulin sensitivity, lower blood sugar levels, reduced appetite, and digestion benefits. (9) Resistant starch is technically a type of carbohydrate that ‘resists’ digestion in the small intestine and instead ferments in the large intestine, where it acts similarly to soluble fiber. During fermentation, resistant starch feeds beneficial gut bacteria, producing short-chain fatty acids like butyrate that support colon health, reduce inflammation, and improve metabolic health.(9) While not classified as traditional dietary fiber, resistant starch plays a similar role in promoting digestive health and can be found in foods like cooked and cooled potatoes, green bananas, legumes, and whole grains.(9) All these foods also contain dietary fiber, so it’s safe to say that resistant starch and fiber can go hand in hand!

Simple Ways to Get More Fiber Daily

Most people probably “know” what fiber is. The problem is that the average American only eats about 16 grams of fiber a day, even though it’s recommended that women should aim for 25 grams a day, and men 38 grams.(10) Now you're probably asking yourself, well how can I eat more fiber on a daily basis? The good news is, fiber is in a vast majority of whole foods, you just have to choose the right ones! Try to choose whole grains over refined grains as often as possible. The reason behind this is that whole grains are minimally processed leaving the grain together, whereas refined grains are stripped of their germ and fiber-rich bran.(7) An example of choosing whole grains over refined grains includes cooking brown rice instead of white rice. Apart from brown rice, other good sources of whole grain include quinoa, whole-wheat bread, oatmeal, barley, and buckwheat products.(7)

For your next tip on eating more fiber, one word; vegetables.The FDA recommends that adults consume 2-3 cups of vegetables a day, meaning you should be incorporating raw or cooked vegetables in almost every meal. Some of the vegetables with the highest fiber content include green peas (1 cup= 9 grams), broccoli (1 cup= 5 grams), brussel sprouts (1 cup= 4.5 grams), and corn (1 cup-= 4 grams). (4)

Last, but certainly not least, in the world of fiber you can never forget about fruits. The FDA recommends that adults should aim for at least 2 cups of fruit per day.(5) If you want to target eating fruits with the highest fiber content, it’s best to make sure you add berries to your mix. Raspberries and blackberries have 8 grams of fiber per cup! (4) If you are looking for fruit that contains both insoluble and soluble fiber, try pears or apples. There are so many different ways to incorporate all these fruits into your diet. Throw them into a smoothie, on top of a salad, or just eat them on their own and enjoy their unique sweet taste!

At this point, it’s clear that fiber isn’t just a health buzzword, it’s a fundamental component of your diet that plays a crucial role in everything from digestive health to heart function, blood sugar regulation, weight management, and even long-term disease prevention.(2) Whether it’s the gel-forming power of soluble fiber found in foods like oats and citrus fruits, or the stool-bulking benefits of insoluble fiber in whole grains and vegetables, both types work together to keep your body running efficiently and smoothly. Let’s not forget resistant starch, the under-the-radar cousin of fiber that fuels the good bacteria in your gut and supports a healthier microbiome.(9) It's proof that nutrition isn’t just about what you digest, but also about what your gut bacteria digest, too.

The problem? Most people are still falling well short of daily recommendations, often getting less than half of what their bodies need. But the solution doesn’t require drastic change. In fact, it can start with small, sustainable swaps: trade white rice for quinoa or brown rice, toss a handful of berries on your morning oatmeal, add lentils to your soup, or enjoy a crisp apple as a snack. It’s about building a plate that naturally includes fiber from a variety of plant-based sources, and making those choices feel satisfying and not restrictive. Just remember to increase fiber gradually and drink plenty of water, adding too much too quickly can lead to bloating or other gastrointestinal discomfort.

Fiber isn’t about dieting or following a trend, it’s about laying the foundation for a healthier you. Every extra gram you incorporate makes a difference. So the next time you build a meal, think of fiber as more than just a digestive helper. Think of it as a tool for your body to support your energy, longevity, and vitality!

Sources

Two Faces of Fiber: Soluble and Insoluble Fiber Explained.

Smart Summer Sipping: Your Guide to Hydration & Electrolytes