You’ve heard that fiber is good for you, right? Are you wondering which types of plant based foods contain fiber? Do you want to make sure you get enough fiber in your diet? 

You’re in the right place! In this Essential Guide to Plant Based Fiber, we cover:

  • What plant based fiber is.
  • How fiber works in the body, and how that is related to health.
  • How much fiber you need and how to get it.
image depicting foods high in plant based fiber including fruits, vegetables, whole grains, nuts and seeds

What is plant based fiber?

Fiber is a group of complex carbohydrates that our body cannot digest. I’ve always thought that was a confusing definition so let me explain. 

Complex carbohydrates simply means that fiber is made up of long chains of starch molecules. This in contrast to refined or simple carbohydrates (like glucose, the basis of sugar) which are smaller and less complex molecules. 

The human body does not have the enzymes necessary to completely break down fiber. We do have the enzymes to break down simple carbohydrates like glucose, galactose and lactose. 

Indigestible simply means that once we eat fiber, it ends up in our digestive tract in larger molecules than refined carbohydrates do. 

This indigestibility may sound like a disadvantage, but it is actually its health-promoting super power. More on that later. 

Scientists generally classify fiber in two ways: 1) dietary fiber versus functional fiber and 2) soluble versus insoluble fiber. 

These classifications are often used on food labels, so it can be helpful to understand the different ways in which you will see fiber described on packaging. Then, you can work with your registered dietitian (like me) to better understand how the different types of fiber can support your individual health goals. 

Most fiber comes from plants. But, there are some exceptions to this. For our purposes, any fiber that comes only from plants is considered plant-based fiber.

Dietary versus functional fiber

This classification of fiber describes how it is found in the food supply. 

Dietary fiber

Dietary fiber is the type of fiber that naturally occurs in foods. Below are some examples. 

Lignins: I know I just said that fiber is a carbohydrate. There are a couple of exemptions. Lignins are not technically a carbohydrate but rather a biological compound found in the cell walls of plants. 

Cellulose and hemicellulose: the matter that makes up cell walls in plants that contain glucose, or in the case of hemicellulose other naturally occurring sugars. I like to think of them as “roughage.” 

Beta-glucan: a type of fiber uniquely found in oats and barley. 

Pectin: if you like to make your own jams and jellies, you are likely familiar with pectin. It is a type of fiber found in berries and other fruit that has a gel-like property when dissolved in water.

Gums: a common example is guar gum which is extracted from a seed and used to thicken food products. 

Inulin and oligofructose: these are types of fibers commonly found in vegetables like onions and Jerusalem artichokes. 

Resistant starch: this type of carbohydrate is found inside the cell walls of plants like bananas and beans. It is also a naturally occurring process when certain foods, like potatoes and rice, are cooled and then reheated. 

Functional fiber

Functional fiber is extracted from its natural source (like those examples above) and made into a dietary supplement, or added to food for a variety of functional and nutritional reasons. 

The Institute of Medicine requires that in order for a compound to be called functional fiber, it must be beneficial to human health in some way. 

The list of functional fiber (and functional foods in general) is always growing, but here are a few examples. 

Psyllium: if you’ve ever taken Metamucil, a plant based fiber supplement, you are familiar with the effects of this fiber that comes from the seeds of the plantago ovato plant.

Chitin and chitosan: technically not a plant based fiber, chitin and chitosan is found in the shells of crustaceans like crab and lobster. It is used as a food additive to thicken or emulsify products, among other uses. 

Fructooligosaccharides: complex chains of sugar molecules found in plant foods like onions, garlic, chicory root and Jerusalem artichokes.

Galactooligosaccharides: considered prebiotics because they feed the “good” bacteria in the gut. 

Polydextrose and polyols: these are synthetic carbohydrates that are used as sugar substitutes in food. 

Total fiber

Total fiber is dietary fiber and functional fiber to understand the total amount of fiber you are eating. For example, around breakfast time you take a fiber supplement (functional fiber) and fresh fruit (dietary fiber) with your eggs. 

How fiber works: solubility, insolubility, viscosity and fermentable 

The chemical properties of fiber may sound like a dry topic, but fiber’s chemical properties have big implications for its impact on human health. Let me explain!

Soluble versus insoluble

Solubility is how well a substance dissolves in a liquid. Soluble fiber dissolves in water. For example, beta-glucan, a fiber found in oats, is a soluble fiber. Beta glucan is also a fermentable fiber so it may have gut health benefits. 

Insoluble fiber does not dissolve in water. Cellulose, the material that makes up the cell walls of plants, is a great example of insoluble fiber. Think of the “roughage” that comes from lettuce. 

Viscosity

The best way to think of viscosity is how gel-like a substance is. Some fibers are viscous and form gels in the digestive system. Psyllium, the active ingredient in some fiber supplements, is a good example of a viscous fiber. Its gel-forming ability has a laxative effect. 

Fermentability

Animals, like humans, are not the only creatures that like fiber. Fermentable fiber is broken down into smaller bioactive compounds by bacteria in the gastrointestinal tract. 

Fiber that ferments and supports the growth of beneficial bacteria is called prebiotic fiber. Inulin is a type of fermentable fiber found in asparagus. Inulin is also added to a variety of foods. 

Why is fiber important for health?

Fiber supports healthy cholesterol levels and overall heart health

Highly viscous and soluble fibers like beta glucan and psyllium fiber may support a reduction in total and LDL cholesterol. The fiber traps bile a molecule that helps regulate how your body metabolizes fat so that the cholesterol is released in your stool thereby reducing the total amount in your body. 

Lower total cholesterol and LDL cholesterol means decreasing your risk for heart disease. This has led to a FDA nutrient claim on some products indicating the link between consumption of soluble fiber and reduced risk for heart disease. 

For example, have you ever noticed this message on the Quaker Oats container: “3 grams of soluble fiber from oatmeal daily in a diet low in saturated fat and cholesterol may reduce this risk of heart disease. This cereal has 2 grams per serving.” 

Fiber may help regulate your blood sugar levels 

There is some evidence to suggest that soluble fiber, specifically psyllium, may support good glycemic control in people with or without type 2 diabetes. The viscosity of the fiber slows the breakdown of nutrients allowing for a more gradual absorption of carbohydrates. 

Soluble, viscous fiber may also trigger the release of a hormone called GLP-1 which improves insulin secretion, helping your body absorb carbohydrates at an appropriate rate. 

There is not enough research yet to say that fiber intake can prevent type 2 diabetes, but consuming enough fiber may help reduce risk. Vitamins and minerals, like magnesium, found in fiber containing foods may also support a reduction in diabetes risk. 

Plant based fiber can help improve regularity

Simply put, increasing your fiber intake can help you poop more regularly to avoid constipation. Research suggests that fibers that are not fermented by bacteria in the gut are most supportive of bowel movement regularity. 

Working with a dietitian can help you identify which type of fiber is right for you. Some examples of regularity-promoting fibers include wheat bran and psyllium fiber. 

High fiber plant based foods may help prevent certain cancers

Researchers think that fiber intake can help reduce risk for certain types of cancer because the bacteria that digest fiber produce compounds that displace “bad” bacteria in the gut.

It is also possible that the improved regularity that can come from taking in more fiber supports the release of carcinogens in the body. 

Either way, there is significant evidence that increased fiber intake can help protect you against cancer, especially colorectal  cancer. 

How much plant based fiber do you need and how can you be sure you are getting enough dietary fiber?

Now we know how and why fiber is good for you. So, how much do we need to enjoy those benefits?

  • For adults 50 and younger, the recommendation for total fiber intake is 38 grams per day for men and 25 grams per day for women.
  • If you are older than 50 years of age, the recommended amount lowers to 30 grams per day for men and 21 grams per day for women. 

Most Americans do not get enough fiber. 

Plant based fiber and nutrition facts panel 

On packaged products, the packaging and nutrition facts panel is the best way to tell how much fiber a product contains. 

Look for dietary fiber on the nutrition facts panel. Displaying the amounts of insoluble and soluble fiber in the total dietary fiber amount is optional for manufacturers so you are unlikely to see it very often. Here it is on the facts panel for oatmeal 

Plant based fiber and front of package health claims

The front of package is also a good place to look for information about fiber. The FDA regulates health claims related to fiber and other nutrients. 

A product that contains 20% or more of the daily value for fiber can be described as “high” in fiber. The Daily Value for fiber is 28 grams. If the product contains 10-19% of the daily value, then the manufacturer may claim that the product is a good source of fiber.

Here are three examples of  FDA-approved health claims on packaging that indicate the product is a good choice when increasing your fiber. 

 “Diets low in saturated fat and cholesterol and rich in fruits, vegetables, and grain products that contain some types of dietary fiber, particularly soluble fiber, may reduce the risk of heart disease, a disease associated with many factors.”

Development of heart disease depends on many factors. Eating a diet low in saturated fat and cholesterol and high in fruits, vegetables, and grain products that contain fiber may lower blood cholesterol levels and reduce your risk of heart disease.”

“3 grams of soluble fiber from oatmeal daily in a diet low in saturated fat and cholesterol may reduce this risk of heart disease. This cereal has 2 grams per serving.” 

inforgraphic depicting how to get enough plant based fiber

How do I make sure I am getting enough plant based fiber?

The best source of fiber comes from plant based foods like legumes (beans and peas), nuts, whole grains, fruits and vegetables. 

Eating a wide variety of these foods is key to getting enough plant based fiber in your diet. Here are some tips for getting more plant based fiber in your diet. 

  • Eat at least five servings of fruits and vegetables daily. Remember that frozen, canned and dried produce are nutritious and budget friendly options. Just look out for added sugars. 
  • Try making half of the grain products you eat from whole grain sources. Eating oatmeal for breakfast is a great way to do this. 
  • Enjoy beans or lentils at least once weekly. 
  • Regularly consume nuts (1-2 ounce per day) and popcorn in place of salty snacks and candy. 
  • There is no need to memorize the fiber content of foods,but it can be helpful to familiarize yourself with what foods are the best source of fiber. 
  • Simply saying “I will eat more fiber” is unlikely to result in increased fiber intake. Try setting a numerical goal and building your weekly meal plan around this. Another great reason to work with a registered dietitian who can help. 

High fiber plant based foods

Lastly, try delicious vegetarian foods high in fiber with new recipes. Make sure to download your free copy of my Plant-forward Meal Prep Made Easy Guide with tons of fiber-containing recipes. 

This high fiber foods chart features high fiber plant based foods.

Other considerations

While it is important for most people to get the recommended amount of fiber per day, there are some considerations. 

It is important to remember that when you increase your fiber intake, you should also increase your water intake. Everyone’s needs are different but a common cause of GI distress in plant based eaters is too much fiber without enough liquid. 

People struggling with IBS have a complicated relationship with fiber, specifically fermentable fiber. If you need help meeting your fiber goals and managing your IBS symptoms, I highly recommend working a registered dietitian who can help you. 

Final thoughts

Fiber is a group of complex carbohydrates that our body cannot digest. Plant based fiber comes from only plant-based sources. 

Fiber is classified as dietary fiber or functional fiber. Its health promoting qualities are based on its chemical properties of soluble, insoluble, viscosity and gel-forming properties. 

Adequate fiber intake promotes lower cholesterol levels, overall heart health, blood sugar control, improved regularity and possible reduction in cancer risk. 

The best way to get enough fiber is to consume plant based foods on a daily basis and try new recipes and fun ways to include fiber-containing foods into your diet.

infographic depicting basic information about plant based fiber

Sources: Linus Pauling Institute and FDA.

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