5 Good Reasons You Should Eat More Fiber Every Day

New research suggests the powerhouse nutrient helps with a variety of health issues

Rachel Nania,

AARP

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En español

Published February 13, 2025

spoonful of muessli, nuts, oats, porridge, seeds and rasberries

Ellis Parrinder/Gallery Stock

It’s common for people to count their calories, log their protein intake and monitor their salt and sugar consumption. But amid all this food tracking, many Americans are forgetting about a key nutrient linked to lower cancer risk, weight loss, better cholesterol and a more robust immune system.

We’re talking about fiber, and research shows that most people in the U.S. aren’t eating enough of it. One study published in 2021 found that only about 7 percent of Americans meet the recommended fiber intake of 14 grams per 1,000 calories of food, or 28 grams for a 2,000-calorie daily diet. A previous study concluded that only 5 percent of Americans consume enough fiber.

“I don’t think fiber is necessarily on people’s radar,” says Katherine Zeratsky, a registered dietitian nutritionist at Mayo Clinic. “And I don’t think fiber gets a whole lot of press.”

One reason: We’re just beginning to discover its benefits throughout the body — beyond keeping it regular, which is the role most people typically associate with fiber. “We’re so early in the science of it,” Zeratsky says. “It’s just a really exciting area.”

Here are five reasons you should add more fiber into your diet this year, based on the latest health research.

The different types of fiber

There are two main types of fiber:

Soluble: Found in oats, peas, beans, bananas, apples, carrots and citrus fruits. This type of fiber dissolves in water and forms a gel-like material in the stomach to slow digestion.
Insoluble: Found in whole-wheat flour, beans, potatoes and vegetables such as cauliflower. This type of fiber doesn’t dissolve in water; it helps keep things moving through the digestive tract and adds bulk to the stool.

Source: Mayo Clinic

1. Fiber can lower your cancer risk

A high-fiber diet has been linked to a lower risk of several types of cancer — from breast to pancreatic — and the reasons run the gamut. Researchers point to fiber’s ability to help the body maintain a healthy weight, and obesity is linked to 13 different cancers. Fiber can also help control blood sugar, and high blood sugar is a risk factor for some cancers.

Some researchers point to fiber-deficient diets as one explanation for the recent rise in colorectal cancer cases in young adults. Fiber helps to dilute stool and move it through the intestine quickly, reducing the time that cancer-causing chemicals and ingredients from food are exposed to the intestinal lining, explains Urvi A. Shah, M.D., a hematologist-oncologist at Memorial Sloan Kettering Cancer Center in New York. Another plus: Microbes living in the gut can ferment fiber into compounds with tumor-suppressive effects, a study in JAMA Oncology explains.

Scientists are studying how fiber can help combat certain blood cancers. Recent research presented by Shah at the 2024 American Society of Hematology annual meeting followed 20 patients with an elevated BMI and a precancerous blood disorder that put them at risk for developing multiple myeloma, a type of cancer that forms in the white blood cells. After incorporating more fiber in their diets, none of the participants progressed to multiple myeloma after one year, the researchers found. Two participants with progressing disease prior to the study showed a significant slowing of their disease progression.

“I don’t think it’s just limited to myeloma,” Shah says. “We’ve shown it for this cancer, but I think these findings are important for probably many cancers.”

Eating a fiber-rich diet may also improve your outcomes if you already have cancer. A study by researchers at MD Anderson Cancer Center and published in Science found that patients with melanoma who ate more fiber-rich foods when they started immunotherapy survived longer than those who didn’t eat much fiber. In fact, every 5-gram increase of daily fiber was associated with a 30 percent lower risk of cancer growth or death.

2. Fiber helps with weight — and weight-related diseases

If you’re trying to lose weight — or maintain your current numbers — doctors and nutrition experts will tell you that fiber is your friend. The body can’t digest fiber like it can other nutrients, so it moves slowly through the stomach and helps keep you feeling full for longer.

“It’s so easy to binge on a bag of potato chips, but we’re not going to binge on carrots, for example, because there’s so much fiber your body is going to feel full; it’s not even going to allow you to binge on something like that,” says Shonali Soans, a dietician in the Integrative Health and Wellbeing program at Weill Cornell Medicine.

“It is satiating, so you automatically eat fewer calories,” Shah adds.

In addition to helping you drop pounds, fiber has been found to help lower blood pressure and keep blood sugar levels in check, which can quell food cravings that accompany sugar spikes and crashes. As opposed to insoluble fiber, soluble fiber — found in foods like oats and beans — can reduce the “bad” cholesterol in your blood, known as low-density lipoprotein, or LDL.

Research has also linked fiber consumption to inflammation reduction. “Because if our digestive health and our blood sugar is normalized and our weight is managed, that’s going to help overall [lower] inflammation,” Soans says.

3. Fiber improves your gut health

It’s impossible to discuss fiber’s health benefits without hitting on its role in the gut, or microbiome — an expansive community of bacteria, fungi and other organisms that live mostly in the large intestine and influence your overall health.

“There’s more and more research coming out on how the gut is connected to everything,” Soans says — and there’s still so much we’re learning.

What we do know is that fiber feeds the “good” bacteria, Zeratsky explains, which keeps them happy and allows them to flourish while simultaneously keeping harmful microbes in check. The byproducts that these good bacteria produce from feasting on fiber help with everything from digestion to mood to immune response.

“I think we recognize the importance, more so now, that fiber plays in the regulation of what types of bacteria are present there,” Zeratsky says.

Shah says the key is to eat a wide variety of foods that are high in fiber — aim for several different sources a day, from leafy vegetables to beans and whole grains. This will help improve the diversity, and “we want a variety of bacteria for good gut microbiome health,” Shah says.

4. Fiber supports your immune system

The gut and the immune system are closely intertwined. In particular, the beneficial byproducts that some bacteria produce from fermenting fiber, called short-chain fatty acids, “have direct effects on the immune system,” Shah says, which helps explain their role in cancer risk reduction.

“I joke, but I think it’s kind of true that fiber is the original immunotherapy,” Shah says.

Some research suggests that diets high in fiber from fruits may reduce respiratory illness symptoms; other studies have linked a high-fiber diet to lower asthma risk. Fiber is even being studied as a possible treatment for long COVID symptoms, especially persisting gastrointestinal issues.

5. Fiber combats constipation

The health benefit that most are familiar with is fiber’s role in keeping you regular, which can become increasingly difficult with advancing age. According to the National Institute on Aging, roughly one-third of people 60 and older experience occasional constipation.

Because the body can’t digest fiber, it adds bulk to the stool, which helps move it through the digestive system more quickly. Some fibrous foods, like prunes and kiwis, are better than others at relieving constipation.

Adding more fiber into your diet

If you’re looking for more ways to add fiber to your diet, small changes can make a big difference.

Top your morning toast or lunchtime sandwich with avocado, Zeratsky suggests — an often overlooked source of fiber. One medium avocado contains about 10 grams of fiber, according to The Nutrition Source at Harvard’s T.H. Chan School of Public Health.

When baking, swap your white flour for whole-grain flours, Soans says, and your white pasta for an alternative, like chickpea and lentil pasta.

A few other high-fiber foods that can help you boost your intake:

Popcorn
Cacao powder (skip the chocolate bar, and add it to a smoothie)
Chia and flax seeds
Almonds
Pistachios
Lentils
Barley
Artichokes

Adding a fiber supplement — whether pill or powder — might seem like an easy way to pack in more fiber, but “it’s not the same” as getting fiber from food, Soans says.

“The reason is because with food, the fiber is coming with all the other nutrients — vitamins, minerals, antioxidants, phytonutrients — all this other good stuff that works synergistically to improve our health,” she says.

Still, some people who experience chronic constipation or who have dietary limitations may benefit from a supplement, Soans adds.

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