How Much Fiber Do You Need?

June 2nd, 2026

two women shopping for fruit — Dietary fiber comes in two main forms, soluble and insoluble. Most plant foods contain both.

Fiber is one of the biggest keys to staying healthy.

Francis P. MacMillan, Jr., MD

Most people aren't getting enough fiber. How do you know if you are?

Current research links a high-fiber diet to better digestive, heart, and gut health.

Experts recommend that adults get 25 to 38 grams of fiber each day, but most of us only get about half that amount.

Getting enough fiber also helps stabilize blood sugar, lower LDL cholesterol, and reduce the risk of chronic diseases like heart disease, type 2 diabetes, and colon cancer.

“Eating a diet rich in fiber can help prevent the development of disease and premature aging,” says Gastroenterologist Frank P. MacMillan, Jr., MD of Dartmouth Hitchcock Clinics Manchester.

Why aren’t we getting enough fiber?

Seventy-five percent of American grocery store shelves consist of ultra-processed foods. Those foods lose most of their natural fiber during processing, MacMillan explains. And the more we eat packaged and fast foods instead of whole plant foods, the less fiber we consume.

People eat less fiber than the recommended guidelines, about 16 grams per day compared to 25 to 38 grams.

A 2023 study describes an “evolutionary mismatch” theory that our bodies evolved for diets rich in minimally processed, high-fiber plant foods. But the modern industrialized diets we eat today are mostly low in fiber.

This mismatch between what our bodies need and what we eat now may help explain why chronic diseases like obesity, type 2 diabetes, heart disease, and colon cancer are on the rise.

Why does fiber matter?

Fiber keeps your digestion regular and feeds your gut microbiome, the trillions of bacteria living in your digestive tract.

Unlike sugars or starches, fiber isn’t digested in your small intestine but moves to your large intestine, where it’s fermented by gut bacteria.

“When you eat fiber, gut bacteria break it down through fermentation, making important compounds that help keep your colon healthy,” says Catherine Giguere-Rich, RDN, LD, a registered dietitian and nutritionist who specializes in gastroenterology at Dartmouth Health.

These compounds, such as short-chain fatty acids, help reduce inflammation, strengthen your gut lining, and support your immune system, she says.

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What’s the difference between soluble and insoluble fiber?

Dietary fiber comes in two main forms, soluble and insoluble. Most plant foods contain both.

“Consuming 25 to 30 grams every day of total fiber, both insoluble and soluble forms, has been shown to reduce death from cardiovascular disease by up to one-third,” says Jean Copeland, RDN, LD, a registered dietitian and nutritionist, and board-certified specialist in gerontological nutrition at Dartmouth Hitchcock Medical Center’s (DHMC) Heart and Vascular Center.

Fiber lowers LDL (“bad”) cholesterol, helps control blood sugar, and reduces inflammation. People who eat more fiber also tend to have lower blood pressure and a lower risk of heart disease and stroke.

Soluble fiber dissolves in water and forms a gel in your gut. This helps lower cholesterol and stabilize blood sugar.

Soluble fiber is found in foods like:

Oats
Beans
Lentils
Apples
Citrus fruits
Carrots
Chia seeds
Flax meal
Barley

Benefits of soluble fiber:

Helps lower LDL (“bad”) cholesterol
Helps stabilize blood sugar
Keeps you full longer
Supports healthy gut bacteria.
Insoluble fiber doesn’t dissolve in water. It adds bulk to your stool and helps keeps your bowel movements regular.

Foods high in insoluble fiber:

Whole grains
Bran
Nuts
Seeds
Cauliflower
Green beans
Potato skins
Leafy greens

Benefits of insoluble fiber:

Helps prevent constipation
Promotes regular bowel movements
Supports colon health
Helps your body use insulin better and keeps blood sugar under control.

How to eat more fiber

Experts say to start slow so your digestive system can adjust.

MacMillan suggests starting with about 5 grams of fiber per day and increasing it by 1 to 2 grams every one to two weeks.

To put that into perspective:

1 medium pear = 5-6 grams

1 cup raspberries = 6-8 grams

½ cup black beans = 7-9 grams

1 cup cooked oatmeal = 4-5 grams

1 medium sweet potato with skin = 4-5 grams

Easy ways to get more fiber

Add berries: Try a bowl of oatmeal with berries, like strawberries, blackberries, blueberries, or raspberries. If you’re looking for the highest fiber content, raspberries and blackberries are your best bet. Fresh or frozen berries work.

Choose whole grains: Choose brown rice, quinoa, or whole wheat pasta, and double-check that whole grain flour (not white flour) is the first ingredient in your bread.

Load up on non-starchy vegetables: Start dinner with 3 cups of a tossed salad, which contains 2 grams of fiber. Add fiber-rich vegetables, fresh or frozen—like spinach or broccoli—to your dishes.

Don’t forget beans and legumes: Add lentils, peas, or a variety of beans, like pinto, kidney, lima, navy, or chickpeas to salads, soups, stews, and casseroles.

Snack on fruits, vegetables, nuts, and seeds: Add apples, pears, and bananas, as well as baby carrots, to meals and snacks. Nuts and seeds, including almonds, sunflower seeds, or pistachios, make for a quick, fiber-rich snack.

“If you’re getting enough fiber, then you’re lowering your risk for health complications like diabetes, obesity, and heart disease,” MacMillan says. “Fiber is one of the biggest keys to staying healthy.”