7 Health Benefits of Fiber
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Medically reviewed by Aviv Joshua, MS
Dietary fiber is a type of carbohydrate that your body can’t fully digest. It's found in plant foods like grains, vegetables, fruits, nuts, and seeds. Fiber offers a wide variety of health benefits. However, most people in the United States only consume about half the daily recommended amount.
There are two types of fiber: soluble and insoluble. Soluble fiber slows digestion. It turns to gel when it dissolves in water, affecting your blood sugar and cholesterol levels. Insoluble fiber speeds up digestion and keeps your gut running smoothly. It doesn’t dissolve or enter your bloodstream, so it doesn't affect blood sugar.
Both types of fiber offer a variety of health benefits. Still, it's possible to have too much fiber. There are also some safety considerations when taking fiber supplements.
Benefits of Fiber
Fiber is often associated with preventing constipation and supporting digestion. It offers a variety of potential health benefits including diabetes and cancer prevention, as well as weight loss. Many of these benefits are connected to gut health.
1. Prevents Blood Sugar Spikes
Type 2 diabetes is a major health concern in the U.S. About 11% of Americans have diabetes, and up to 95% of those people have type 2 diabetes. Both prediabetes and metabolic syndrome are present in about 33% of the population.
Metabolic syndrome is a group of medical conditions that increase your risk for diseases such as heart disease, stroke, and type 2 diabetes. Key factors include high blood sugar, blood pressure, and cholesterol.
Managing diabetes requires keeping your blood sugar levels stable. Fiber is a carbohydrate that doesn’t spike your blood sugar because it's not digested.
2. Supports Gut Health
Fiber acts like a broom, moving the contents of your intestines along, but it may do more than that. Everyone has trillions of gut bacteria living in their intestines. Your gut contains good bacteria that help you digest food and keep bad bacteria at bay. This is known as your microbiome.
Diets high in dietary fiber positively affect your gut microbiota, which improves full-body health. Scientists are still learning about the gut microbiome, but research shows that a healthy gut influences health factors like blood glucose (sugar), cholesterol, and insulin levels.
3. May Reduce Your Risk of Colon Cancer
Many colon cancers begin as benign polyps (non-cancerous growths) in your colon (large intestine) or rectum (end of your large intestine, right before the anus). These growths can take more than 10 years to develop into cancer.
One common belief is that high-fiber diets reduce your risk of developing these polyps in the first place, thereby reducing your risk of colon cancer.
Research shows mixed results about the role of fiber in colon cancer. Some studies show a lower risk while others show no effect at all. Several reviews found a particular risk reduction when participants ate more fiber from cereals or whole grains.
4. May Help You Lose Weight
Over 75% of U.S. adults and 20% of children and adolescents have a weight that's considered overweight or obese. High-fiber foods can support weight loss because they take longer to eat and digest, helping you feel fuller for longer after meals.
One study of 345 participants eating different calorie-restricted diets found that high fiber intake promoted weight loss, regardless of the amounts of different macronutrients the participants ate. Macronutrients are the basic building blocks of food. They include proteins, fats, and carbohydrates.
5. Can Help Prevent Diverticulitis
Diverticulitis is a condition where pouches form in your intestines and become inflamed. It can lead to intense pain and complications. Diverticulitis is very common in the U.S. Over 30% of adults live with it. That percentage increases to 70% over the age of 80.
For a long time, patients with diverticulitis were advised to avoid nuts, seeds, or high-seed fruits like strawberries, for fear that those foods could get stuck in the pouches and cause inflammation. However, studies show that high-fiber diets with a focus on fruits, vegetables, and whole grains are strongly associated with less diverticular disease.
6. May Reduce Your Risk of Breast Cancer
Each year, about 240,000 people in the U.S. are diagnosed with breast cancer. It's the leading cause of cancer death among minorities.
One review of 20 studies found that people who ate more fiber had a lower risk of breast cancer. Most reviewed studies relied on food frequency questionnaires, where participants were asked what foods they had eaten recently.
Studies like these are flawed, because participants might not remember accurately or might feel embarrassed to admit what they ate. More research is needed to determine clear connections between fiber and breast cancer.
7. May Improve Your Heart Health
Heart disease is the leading cause of death in the U.S., with one person dying every 33 seconds. Many studies have studied fiber’s effect on heart disease. Results show that high-fiber diets tend to have protective effects against heart disease and atherosclerosis (plaque build-up in arteries).
It’s important to note that many of these studies were observational and were not able to determine if higher fiber intake clearly reduces the risk of heart disease. More research is needed.
Good Sources of Fiber
High-fiber foods are abundant and easy to find. Here are some common sources of fiber:
Leafy greens like lettuce, Swiss chard, and spinach
Cruciferous vegetables like broccoli and Brussels sprouts
Root vegetables like carrots and potatoes
Beans, legumes, and peas
Nuts and seeds
Fruits (e.g., apples, kiwis, tomatoes, avocado)
Whole grains (e.g., oats, barley, quinoa, brown rice)
Here's the fiber content of a few specific high-fiber foods:
Black beans: 9 grams (g) per ½ cup, or 32% of the daily value (DV)
Avocado: 4.6 g per ½ fruit, or 18% of the DV
Sweet potato: 4 g in a medium potato, or 15% of the DV
Dried apples: 4 g in ½ cup, or 15% of the DV
Blackberries: 3.5 g in 1 cup, or 12.5% of the DV
Whole grain bread: 3 g in 1 slice, or 11% of the DV
How To Use Fiber
You can increase your fiber intake by eating more whole foods like fruits, vegetables, beans, nuts, seeds, and grains. There are also many fiber supplement products on the market. Fiber supplements are sold at pharmacies and grocery stores in forms like powders, caplets, and gummies.
There is no official recommended time of day for taking a fiber supplement. Always consult with your healthcare provider about whether it is safe to take fiber supplements, as they can interact with certain medications. You'll also want to ask them about the recommended dosage.
Dosage
The Dietary Guidelines for Americans, 2020–2025 recommend 22-34 grams of fiber per day, depending on age and sex. You'll want to spread out your fiber intake throughout the day by including high-fiber foods at each meal and snack.
Fiber supplements are not intended to replace high-fiber foods in your diet. However, you might want to talk to your healthcare provider about taking a supplement if you find it difficult to eat enough high-fiber foods during the day.
Supplements can also help soften stool if you're constipated. Your healthcare provider might recommend using one short-term—for example, for a few weeks—if you're particularly blocked up.
Is Fiber Safe?
Fiber is a safe and natural substance in food, but here are a few safety considerations.
It’s important to drink a full glass of water when you take fiber supplements, as water helps move the fiber through your digestive tract. Taking fiber without enough water can also cause the product to swell, which can cause choking.
You may want to avoid some fiber supplements like psyllium if you have certain medical conditions, including:
Heart disease
High blood pressure
Bowel obstruction (when your small or large intestine becomes partly or completely blocked)
Difficulty swallowing
People with irritable bowel syndrome (IBS) should talk with their healthcare provider about whether they need specific types of fiber.
Potential Drug Interactions
Taking a fiber supplement may affect how your body absorbs medications, making them less effective. For example, blond psyllium is a soluble fiber that may decrease your body's absorption of:
Diabetes medications like Glucophage (metformin)
Mental health medications like lithium and Zyprexa (olanzapine), both used to treat conditions like bipolar disorder
Seizure medications like Tegretol (carbamazepine)
Heart medications like Lanoxin (digoxin), which treats heart failure and atrial fibrillation, or A-Fib (irregular heartbeat)
Healthcare providers might recommend taking a fiber supplement about one hour after medications like these.
Where To Find
High-fiber foods are easy to find in grocery stores, particularly in the produce section. Look for foods like lentils, beans, fruits, vegetables, and whole grains at your grocery store and check food labels for fiber content.
Fiber supplements are available in pharmacies and most grocery stores. Supplements are not regulated by the FDA, so check supplement brands and choose one with third-party safety testing.
Can You Have Too Much Fiber?
It's possible to consume too much fiber. Consuming more than the recommended amount may lead to unpleasant side effects like gas and bloating. These side effects might go away as your body adjusts to having more fiber.
Fiber can also reduce your body's absorption of certain minerals, including calcium and magnesium. Luckily, foods high in fiber often contain high levels of minerals as well.
Side Effects of Fiber
While fiber is good for you, you might experience some side effects—especially if you increase fiber too quickly. Most side effects are gastrointestinal, meaning they relate to your digestive system. The most common side effects include:
Cramping
Bloating
Gas
You can reduce your risk of unpleasant side effects by increasing fiber gradually and staying well-hydrated.
Monitor Your Symptoms
Monitor your symptoms when adding more fiber to your diet. Digestive symptoms are a sign that you might need to increase fiber more gradually or spread it out more throughout the day.
You can also talk to a healthcare provider about fiber supplements that might be easier to digest.
A Quick Review
Fiber is part of a healthy diet and may reduce your risk of conditions like heart disease, and diabetes. It supports a healthy gut and may be helpful for weight loss.
Fiber is found in many whole foods, including grains, nuts, seeds, fruits, vegetables, and legumes. Fiber supplements are widely available if you have difficulty including enough high-fiber foods in your diet or if you need digestive support.
Increase your fiber intake slowly and drink plenty of water to reduce unpleasant side effects like cramping and bloating. Always consult with your healthcare provider before trying new supplements.
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