Everything you Need to Know about Fiber

A Registered Dietitian explains everything you need to know about fiber. What it is, what it does for your body and easy ways to eat more.

You have probably heard of fiber and may have even been told to increase the amount you eat.  But what is it?  And what does it do for your body?  

What is Fiber?

Fiber is a type of carbohydrate or lignan that is not digested by your body.  This lack of digestion occurs because the enzymes your gut makes do not work on them.  As a result, they cannot be broken down and used as energy.  They do, however, provide several other amazing benefits for your body!

Types of Fiber

Fiber comes in two main types: soluble and insoluble.

Soluble Fibers

Soluble fibers dissolve when you place them in water. Nutritionists divide them into narrower categories based on two traits: viscosity (how well they form a gel in water) and fermentability (how easily your healthy gut bacteria metabolize them for food).

• Soluble, gel-forming, fermentable fibers: These fibers thicken in water, and your gut bacteria ferment them easily. Because they feed these healthy bacteria, we classify them as prebiotics. They also lower blood cholesterol levels and keep your blood glucose within a healthy range.
• Soluble, gel-forming, non-fermentable fibers: These fibers thicken in water, but your gut bacteria cannot metabolize or ferment them. They still improve your blood glucose and cholesterol levels, while actively preventing and relieving constipation.
• Soluble, non-gel-forming, fermentable fibers: These fibers dissolve in water but never thicken or form a gel. Because your gut bacteria ferment them so well, they also count as prebiotics.

Insoluble Fibers

Insoluble fibers never dissolve, form a gel, or ferment in water. Instead, they act as a natural laxative to keep your digestive tract moving smoothly.

Foods and Supplements with Fiber

Many plant foods naturally provide fiber. Just about every fruit, vegetable, whole grain, nut, seed, and legume contains it in varying amounts.

Manufacturers also isolate fibers to add them directly to foods or supplements. They categorize these manufactured fibers into two main types:

• Plant-Derived Fibers: Processors extract these fibers directly from plant sources. Common examples include psyllium, inulin, oligosaccharides, pectins, resistant starch, and gums.
• Synthetic Fibers: Chemical processes create these fibers in labs. Examples include polydextrose and polyols:
  • Polydextrose: Food companies add polydextrose to products to build bulk and improve texture. Adults can safely consume up to 15 grams per day without issue.
  • Polyols: Ingredients like xylitol, erythritol, and maltitol taste sweet. Though scientists classify them as fibers, manufacturers use them primarily as low-calorie sugar substitutes. Be aware that consuming too many polyols can cause digestive distress, including bloating and a laxative effect.

Health Benefits

There are numerous health benefits that come from eating fiber.  Some of these benefits are specific to the type of fiber you’re eating, and some come from incorporating any type of fiber into your diet. Here are a few of the amazing things they can do:

Help you Stay Full Longer

One benefit you will notice right away when you start eating more fiber, is feeling full for a longer period of time after you eat. This happens because fiber slows down how quickly your body digests the other foods you eat. 

Prevent and Manage Diabetes and Cardiovascular Disease  

Several studies have consistently found an inverse association between eating a high fiber diet and the risks of type 2 diabetes and cardiovascular disease.  This means that the more fiber you eat in your diet, the lower your overall chances of developing or dying from these diseases are. 

Prevent Cancer

Fiber rich diets have also been associated with a reduced risk of several different types of cancer.  This includes cancer of the ovaries, breasts, esophagus, stomach, colon, and pancreas.

Weight Management

Some studies have found eating fiber to help manage body weight.  This is likely due to fiber’s ability to fill you up and keep you full longer, thus preventing overeating. Researchers believe that consuming fiber encourages your body to secrete hormones that control appetite and fullness.

Improve Bowel Regularity (relieve constipation)

Fiber keeps your digestive system on track by preventing constipation and ensuring regular bowel movements occur. This benefit comes specifically from insoluble fibers and soluble fibers that do not ferment. Fruits and vegetables (especially the edible skins), corn bran, wheat bran, nuts, flaxseeds, avocados, and unripe bananas are all excellent sources of these types of fiber. You can also look for the words lignins, cellulose, and hemicellulose on the ingredient lists of food labels to find these types of fiber.

Improve Cholesterol and Blood Sugar Levels

A couple of more well known benefits of fiber are its ability to improve cholesterol levels and regulate your blood sugar.  These benefits come specifically from soluble, gel forming fibers.  You can find this type of fiber in oats, rice, quinoa, peas, beans, avocados, chia seeds, flaxseeds, sunflower seeds, potatoes and fruits.  You can also look for the word psyllium on the ingredient list of food labels for this type of fiber.

Create Healthy Gut Microbiome

Fermentable soluble fibers act as prebiotics because they feed your healthy gut bacteria. These beneficial microbes keep your intestines functioning properly. Growing evidence also shows that they actively prevent diseases and health problems. You can find soluble fermentable fiber in oats, barley, seeds, onions, asparagus, artichokes, apples, berries, legumes, bananas, pastas, and potatoes.  You can also look for the words beta-glucans, guar gum, inulin, oligofructose, oligosaccharides, fructooligosaccharides, pectins and resistant starch on an ingredient list to find this type of fiber.

How much should I eat?

The Food and Nutrition Board created Adequate Intake Levels for fiber based on research finding that roughly 14 grams of fiber per every 1000 calories consumed to have the greatest benefit on your health.  The chart below shows these levels:

Food Sources

In the sections above, I listed several food sources of fiber specific to their type and benefit.  You may have noticed that many foods contain both soluble and insoluble fiber.  As a reminder, you can find fiber in fruits, vegetables, whole grains, nuts, seeds and legumes.  Here is a list of some of the highest fiber containing foods and their amount.  This list is not all inclusive, but a great place to start if you’re interested.

10 Simple Ways to Add Fiber to your Diet

The best thing about fiber is that there are a lot of easy ways to add it to your diet.  “Try these ideas to get started:

1. Eat oatmeal with chopped fruit and nuts for breakfast 
2. Add a sliced tomato and lettuce to your sandwich
3. Find a whole grain bread you like that has at least 2 to 3 grams of fiber per slice
4. Add chia seeds or flaxseeds to your yogurt
5. Eat guacamole and beans with your nachos
6. Make a trail mix out of a variety of nuts and seeds that you like
7. Make (or buy) a hummus dip to go with your veggies
8. Start eating the peel of your apples, pears, peaches, nectarines, cucumbers and potatoes if you have not already
9. Top your pizza with chopped vegetables or salad
10.  Eat an orange (or other fruit) instead of drinking juice 

Recipes

If you are looking for recipes that are high in fiber, then you are in luck! I have created lots of easy and delicious high-fiber recipes. You can find them on my High Fiber Recipes page.

My Dietitian Recommendation

Because fiber offers so many amazing benefits, I am a big advocate for eating it!

When adding more high fiber foods into your diet, start by adding about 3 to 4 grams each week until you reach your goal amount.  Adding too much fiber all at once can cause bloating and cramping.  Drinking enough water each day will also help prevent these symptoms. 

As with most nutrients, I recommend getting fiber in through the foods you eat, rather than jumping straight to a supplement.  After trying this, If you still feel like you’re not getting enough fiber, talk to your dietitian or doctor to see if a supplement is right for you.  

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