Whether it was a doctor, parent, or friend, chances are at least one person in your life has advised, “Make sure you are eating plenty of fiber!” For many of us, fiber is a mystery. We know of a few foods that are high in fiber, like whole grains, but that is the extent of our knowledge. It’s time to solve the mystery surrounding fiber and delve into what it is, what it does for our bodies, and how it can be incorporated into our meals.  

When you hear “carbohydrate,” you likely think of foods like bread, pasta, and bagels, but a carbohydrate is more than that. Carbohydrates are vital to our health and come in a variety of forms, including sugars, starches, and fiber. Fiber is a carbohydrate that the body cannot break down. This means we do not digest or absorb nutrients from it. 

The two types of fiber are soluble fiber and insoluble fiber. Soluble fiber dissolves in water. As it passes through the digestive system, it dissolves into a gel-like substance. Insoluble fiber does not dissolve in water, so it largely maintains its form as it passes through the digestive system. It may sound like fiber doesn’t have much of an impact​​ since it’s just passing through our bodies, but that’s not the case. Despite being unable to digest fiber, we still benefit from it.

Eating fiber can mitigate heart disease and diabetes due to the way it impacts blood sugar and fat absorption. As described by a Mayo Clinic article on fiber, soluble fiber specifically slows down the speed at which the body digests food. This causes the body to absorb the sugar in food more slowly and prevents a sharp rise in blood sugar after a meal. Soluble fiber also reduces the amount of fat the body absorbs, which decreases cholesterol levels, according to a Harvard Health Blog article by Monique Tello, MD, MPH. Insoluble fiber helps food move through the digestive tract. It also adds bulk to stool and softens it, which can prevent constipation. Additionally, as fiber moves through the digestive system, it acts as a scrub brush for the intestines. It cleans out bacteria and buildup in the intestines, keeping them healthy.

Where are the best places to find fiber? To begin, you are going to have to bypass the deli and dairy sections of the grocery store because only plant products have fiber. Whole-grain products, legumes, beans, vegetables, and fruits are all sources of fiber. And, while one may expect a fiber-filled diet to be dull, some foods with high amounts of ​​fiber per standard portion are sweet treats like guava and sapote (or chikoo).

Having both types of fiber is important. If you are specifically looking for soluble fiber, beans, citrus fruits, apples, and vegetables are good foods to turn to. If you are looking for insoluble fiber, whole-wheat flour, wheat bran, cauliflower, green beans, potatoes, and—once again—vegetables are good sources.

When thinking about adding grains to your diet, try to go for whole grains, if possible. Whole grains still have the outer layer called the “bran,” which is rich in fiber. Refined grains, on the other hand, have had the bran removed. Even if refined grains are marked as “fortified,” meaning some of their nutrients have been added back, they still won’t have as much fiber as whole grains. Additionally, if you want the full benefits of fiber, you should drink plenty of water. Fiber absorbs water, which allows it to act more effectively. The foods that contribute to a high-fiber diet are also generally healthy, so you’ll boost your overall health by eating them.

Making sure you are getting enough fiber-filled foods can be a challenge. According to the USDA’s report “Dietary Guidelines for Americans, 2020-2025,” women ages 18 and up need between 22 and 28 grams of fiber per day. Men ages 18 and up need between 28 and 34 grams of fiber per day. To put that into context, a gram is about the weight of a paper clip. Eating that much fiber might not sound like a challenge, but it is for most. The guidelines go on to explain that “more than 90 percent of women and 97 percent of men do not meet recommended intakes for dietary fiber.” As surprising as this is, it aligns with the larger trend of 85 percent of all adults getting inadequate amounts of fruits, vegetables, and whole grains, all sources of fiber.

​​​Despite the dismal statistics, there are a variety of quick and easy ways to increase the fiber in your diet. Add a fruit or vegetable along with each meal. Swap your usual breakfast cereal for a whole-grain alternative. When baking, add a sprinkle of uncooked oatmeal to your cake batter. Use dried fruit as a topping on your salad. These are small changes, but together, they can make a difference in your diet.

When I hear the phrase “just passing through,” I think of tourists. They come in and out of a city but don’t have much of an effect. But, when it comes to fiber, even though it is just passing through, it has quite the impact!

Taskeen Khan has a bachelor’s degree in integrative biology and a minor in sustainability, energy, and the environment from the University of Illinois at Urbana-Champaign. She is passionate about science education and communication, as well as research.