Nutrition / Food

Fiber 101: What Is It and What Are the Best Sources?

Find out the major benefits of fiber and what foods contain the most.

Fiber: It keeps you full, it keeps you regular, it protects against cancer. You really can’t ask for much more from a macronutrient.

Fiber is actually a type of carbohydrate. But it can’t be broken down into sugars the way other types are.

Instead, it passes through our bodies undigested and actually aids in a number of physiological processes, particularly the body’s use of sugars and keeping hunger in check.

Keep reading for the intel you need on this crucial carbohydrate—and the best sources of fiber. (Hint: it’s not just in prunes!)

Why do I need fiber?

It keeps you full.

Imagine eating a big, crunchy apple versus drinking a glass of apple juice. The juice won’t fill you up at all; the apple, on the other hand, has staying power. The main difference between the juice and the fruit? Fiber.

“Fiber stays in the stomach for a long time,” says Sharon Palmer, RDN, author of The Plant-Powered Diet: The Lifelong Eating Plan for Achieving Optimal Health Beginning Today and nutrition editor for Today’s Dietitian. “So you feel satisfied for an extended period of time.”

Fiber-rich foods also typically require a lot of chewing—think nuts, wheatberries, popcorn. “If it takes you a long time to chew your food, you’re less likely to overeat, because you’re giving the hormones that signal fullness a chance to reach the brain.”

Chewing also stimulates the release of saliva and gastric juices, expanding and filling the stomach. A 2013 Journal of the American College of Nutrition review found that nearly 40 percent of studies using fiber treatments significantly reduced appetite.

It helps lower cholesterol.

Fiber is also crucial for mopping up cholesterol from the blood. “It binds to cholesterol and takes it out of the body,” explains Lara Field, MS, RD, the founder of FEED Nutrition Consulting, based in Chicago. A 2016 British Journal of Nutrition review concluded that diets including about 3.5 grams a day of fiber from oats reduced LDL cholesterol (the “bad” kind) by 4.2 percent.

It may reduce your cancer risk.

Colorectal cancer risk may drop as fiber intake increases. “Fiber provides bulk, which helps ensure regular bowel movements,” Field says.

The quicker waste moves through your system, the less time your colorectal tract is exposed to potentially hazardous, cancer-causing substances in stool. Talk to your doctor more about your individual risk of colorectal cancer before changing your diet.

It assists in healthy aging.

If promises of a fuller belly and more satisfying bathroom breaks aren’t enough to sway you, consider this: Research published by The Gerontological Society of America recently found that, when it comes to successful aging (characterized by an absence of disability, depressive symptoms, cognitive impairment, respiratory symptoms, and chronic diseases including cancer, coronary artery disease, and stroke), fiber intake matters more than a person’s total carbohydrate intake, sugar intake, or other nutritional factors.

Researchers found that those who had the highest intake of fiber had an almost 80 percent greater likelihood of living a long and healthy life over a 10-year period. This means they were less likely to suffer from diseases and disorders like hypertension, diabetes, dementia, and depression.

How much fiber do I need?

The average person needs between 25 and 35 grams of fiber a day. (The average American nets just 15.) If that sounds overwhelming, Field recommends instead trying to eat five servings of produce per day. Most fruits and vegetables are fiber-rich. She also recommends incorporating a few servings of whole grains, such as quinoa, whole wheat pasta, or brown rice into your daily diet.

Are there different types of fiber?

There are two types of dietary fiber: soluble and insoluble. Soluble fiber is found in fruits, vegetables, legumes, and grains. It dissolves in water. This type of fiber helps cut cholesterol, keeps you full, and helps control blood sugar.

Insoluble fiber is found in grain brans, fruit pulp, vegetable peels and skins. It doesn’t dissolve in water. This type of fiber is most commonly linked to cancer prevention and a more regular digestive system.

What are the best sources of fiber?


Almonds, walnuts, cashews, peanuts. These crunchy little gems combine fiber with healthy protein and fat, Palmer says. One ounce of almonds (about 23 nuts), for example, provides 3.5 grams of fiber.

Bonus: People who munch a handful of nuts per day are 20 percent less likely to die from any cause compared with non nut-eaters. Other research has found that eating almonds instead of high-carb snacks may lower heart disease risk by decreasing dangerous belly fat.


One medium apple contains four grams of fiber. Other smart options from the fruit basket include a large pear (7 grams), an orange (4 grams), ½ cup prunes or figs (6 and 8 grams, respectively), or 1 cup berries (8 grams).

Beans and Lentils

One cup of cooked lentils or black beans offers 15 grams of fiber. Both are also excellent sources of protein. They also contain an impressive roster of antioxidants, vitamins, and minerals, including iron, potassium, and zinc.

Chia Seeds

Chia seeds are made up ¾ grams of insoluble fiber and ¼ of soluble fiber. Sprinkle these tiny black or white seeds over anything—yogurt, kefir, oatmeal, and salads. Two tablespoons yields an impressive 11 grams of fiber. They’re also incredibly rich in omega-3 fatty acids, which help reduce cholesterol and high blood pressure.

Rolled Oats

Oats are an excellent source of soluble fiber. One cup of cooked oatmeal contains 4 grams of fiber. Bump it up with toppings such as dried figs (about 4 grams in ¼ cup), flax seeds (7 grams in 2 tablespoons), and a small handful of chopped nuts.

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