Medically reviewed by Dr. Dan Wool, NMD

 Arizona-licensed Naturopathic Physician and Gastroenterology Specialist

 Updated: November 11, 2025

Summary: 

• What is Dietary Fiber and Types: Dietary fiber is plant-based food components your body cannot digest or absorb, passing intact through stomach, small intestine, and colon. Soluble fiber dissolves in water forming gel-like substance that slows digestion, lowers cholesterol and glucose levels, increases satiety found in beans, lentils, oats, apples, and citrus fruits. Insoluble fiber doesn't dissolve, adds stool bulk, promotes regular bowel movements, prevents constipation found in whole grains, brown rice, vegetables, nuts, and berries.
• Daily Fiber Requirements and Health Benefits: Women need 22-28 grams daily (varies by age), men need 28-34 grams, but average Americans consume only 16 grams—half the recommended amount. Fiber supports digestive health preventing constipation and promoting healthy gut microbiome, improves heart health by reducing LDL "bad" cholesterol, controls blood sugar by slowing sugar absorption, and aids weight management by increasing fullness and reducing cravings for sustained satiety.
• When to Use Fiber Supplements and Precautions: Consider fiber supplements for chronic constipation, irritable bowel syndrome (IBS), restricted diets limiting fiber-rich foods, post-surgery recovery, or additional cholesterol and blood sugar management support. Common supplements include psyllium husk, methylcellulose, wheat dextrin, and inulin with different properties requiring healthcare provider consultation. Fiber supplements may interfere with medication absorption—take one hour before or two hours after medications.
• Safe Fiber Intake Guidelines and Food Sources: Increase fiber gradually over days or weeks to avoid bloating, gas, and cramping from sudden dietary changes. Stay hydrated as fiber requires water absorption for proper digestive system movement and constipation prevention. Balance soluble and insoluble fiber through variety of plant sources including legumes (lentils, chickpeas), whole grains (quinoa, oats), fruits (berries, apples), vegetables (broccoli, carrots), and nuts/seeds (almonds, chia seeds, flaxseeds) for optimal health benefits.

Dietary fiber is one of the most overlooked yet essential components of a healthy diet. Its many benefits range from supporting your overall digestive health to reducing the risk of chronic diseases. Still, the focus of many popular diets seems to be mainly on the macronutrients - proteins, carbohydrates, and fats.

The fact that most people fall short of the recommended daily intake of fiber. Meanwhile, what is and is not fiber is not clear to many. 

In this article, we’ll look at how much fiber you need, when supplementation might be appropriate, and how to exercise caution when increasing your fiber intake. Whether you're having digestive issues, managing weight, or simply aiming to improve your overall health, understanding fiber is a foundational step.

What Is Dietary Fiber?

Dietary fiber is contained only in plant food, and it refers to those parts that your body can't digest or absorb. Unlike fats, proteins, or digestible carbohydrates, fiber passes almost intact through your stomach, small intestine, and colon, until it leaves your body [1]. We can differentiate two main types of dietary fiber:

1. Soluble fiber - this type dissolves in water and turns into a gel-like substance, which slows down digestion. It can help overall digestive health by bulking up your stool and helping with diarrhea, lowering blood cholesterol and glucose levels, while also increasing the feeling of satiety and helping with weight management [1]. Foods rich in soluble fiber are pulses (beans, lentils, dhal), fruit (apples, pears, citrus fruits, carrots), and grains and seeds (oats, barley, flaxseeds).
2. Insoluble fiber - doesn’t dissolve in water, as the name suggests. It adds bulk to stool, which aids food and waste in moving through the digestive system more efficiently. This improves your bowel movements' regularity and prevents constipation. Foods such as whole grains, bran, brown rice, vegetables (e.g., greens, broccoli, zucchini), fruit (e.g., blackberries), and nuts all contain insoluble fibre [1].
   

Most plant-based foods contain a mix of both types of fiber, and both are important for your health. 

How Much Fiber Do You Need Every Day?

The recommended daily intake of fiber varies between 22 -34 grams per day, and it depends on your age and sex.

Below are the general guidelines according to the U.S. Department of Agriculture and the National Academy of Medicine [2]:

Women by age:

• 19–30: 28 grams
• 31–50: 25 grams
• 51 and older: 22 grams

Men by age:

• 19–30: 34 grams
• 31–50: 31 grams
• 51 and older: 28 grams

Even with all the scientific evidence and continuous recommendations to consume sufficient fiber daily, the average American eats only about 16 grams of fiber per day [2]. That’s barely half of what’s needed for optimal health, and being consistently below the recommended daily amount can have serious consequences in the long term.

Why Fiber Matters

Fiber has a crucial role in maintaining several aspects of your health:

• Digestive Health: It adds bulk to your stool and helps prevent constipation (and in the case of soluble fiber, can help you recover from diarrhea). It also supports a healthy gut microbiome [1].
• Heart Health: Soluble fiber can help lower total blood cholesterol levels by reducing low-density lipoprotein (LDL), also known as 'bad' cholesterol [1].
• Controlling Blood Sugar: All fiber, especially soluble fiber, can slow the absorption of sugar and help improve blood sugar levels [1].
• Weight Management: High-fiber foods are more filling, creating the feeling of satiation and can help you eat less, curb cravings and stay satisfied longer [2].

When to Consider Fiber Supplements

While having a balanced diet including fiber-rich whole foods is the preferred way to ensure you have a sufficient fiber intake, supplements can be helpful on certain occasions, such as when you:

• Have digestive issues like chronic constipation or irritable bowel syndrome (IBS);
• Are on a restricted diet that limits fiber-rich foods;
• Are you recovering from surgery or illness and need a gentler way to increase fiber intake?
• Are trying to lower cholesterol or manage blood sugar and need additional support.

Common types of fiber supplements include psyllium husk, methylcellulose, wheat germ or dextrin and inulin. Each has different properties and can be used in different situations depending on your specific case, so it’s best to consult a healthcare provider or a naturopathic doctor to determine which is the right supplement for you [3].

Dietary Fiber "Rules of Thumb" and What to Watch Out for

Even though fiber is good for you, if you increase your intake too quickly or without drinking enough liquids, this can lead to undesirable and often uncomfortable side effects. Here’s what you need to consider:

1. Start Slowly(!): A sudden increase in your fiber intake, especially if your diet has been lacking in fiber for a while, can cause bloating, gas, and cramping. Add fiber-rich foods gradually, over several days or weeks, to allow your digestive system to adjust and avoid discomfort [3].
2. Stay Hydrated: Fiber, both soluble and insoluble, works best when it absorbs water. Ensuring you drink plenty of fluids will help fiber move through your digestive system and prevent constipation [3].
3. Balance Soluble and Insoluble Fiber: Like everything related to your diet, exercise moderation. Too much of either type of fiber can cause imbalances. Aim for a variety of fiber sources to get both types. This shouldn’t be too difficult, especially since you have so many plant foods to include in your daily meals, the majority of which look and taste great.
4. Watch for Interactions: Fiber supplements can interfere with the absorption of certain medications. Always take them at least one hour before or two hours after other medications [3].

Best Food Sources of Dietary Fiber

The best sources of fiber is your diet. Here are some excellent sources of dietary fiber which you can pick ‘n mix to include in your meals daily:

• Legumes: Lentils, black beans, chickpeas;
• Whole Grains: Oats, quinoa, brown rice, whole wheat;
• Fruits: Apples, pears, berries, bananas;
• Vegetables: Carrots, broccoli, Brussels sprouts
• Nuts and Seeds: Almonds, chia seeds, flaxseeds

And below is a sample menu that is a good example of a ‘High-Fiber Day’

• Breakfast: Oatmeal with chia seeds and berries (10g)
• Lunch: Lentil soup with whole grain bread (15g)
• Snack: Apple with almond butter (5g)
• Dinner: Quinoa salad with roasted vegetables (10g)
• Total: ~40 grams of fiber

Consuming Fiber When You Are Following a Special Diet

Getting Fiber on Low-Carb or Keto Diets

These diets often restrict grains and legumes, which are high in fiber. If this is the case for you, focus on non-starchy vegetables, nuts, and seeds to compensate for what you’re restricting and to meet your fiber needs [2].

Replacing wheat: Getting fiber on a Gluten-Free Diet

People avoiding gluten may miss out on whole wheat products. However, there are plenty of gluten-free whole grains like quinoa, brown rice, and certified gluten-free oats [2], which should help you pack enough fiber in your diet.

Signs You May Need More Dietary Fiber

If you’re not getting enough fiber, your body might already be sending you signals such as:

• Frequent constipation
• Feeling hungry soon after eating
• High cholesterol levels
• Blood sugar spikes
• Unexplained weight gain

If you notice these or any other unusual signs, it might be time to evaluate your fiber intake.

Frequently Asked Questions about Dietary Fiber

1. How much fiber should I eat per day?

Fiber needs vary by age and sex. Women need 22-28 grams daily (28g ages 19-30, 25g ages 31-50, 22g over 51). Men need 28-34 grams daily (34g ages 19-30, 31g ages 31-50, 28g over 51). Most Americans consume only 16 grams daily—half the recommended amount. Insufficient fiber intake can lead to digestive issues, high cholesterol, and weight management problems.

2. What are the best sources of dietary fiber?

The best fiber sources include legumes (lentils, black beans, chickpeas), whole grains (oats, quinoa, brown rice), fruits (apples, pears, berries), vegetables (broccoli, carrots, Brussels sprouts), and nuts/seeds (almonds, chia, flaxseeds). Most plant foods contain both soluble and insoluble fiber. A balanced diet with varied plant foods easily provides adequate fiber without supplements.

3. What happens if I increase fiber intake too quickly?

Do you really wanna know? (LOL).  Seriously though - rapidly increasing fiber can cause bloating, gas and cramping. (See?) You'll want to gradually add fiber over several days or weeks to let your digestive system adjust. And stay well-hydrated - fiber works best when absorbing water - too little and it can "sponge up" in the gut, causing discomfort. Drink plenty of fluids to help fiber move through your system and prevent constipation. Balance soluble and insoluble fiber sources (see above) from food vs. supplements if possible for optimal digestive health.

Final Thoughts

Fiber is a foundational nutrient that supports not only your digestive well-being but nearly all aspects of health, such as your heart function and metabolic balance. Paradoxically, in the modern age, we have more access to an even greater variety of foods, but most people don’t get enough good nutrition, including fiber. The good news is that increasing your intake is both simple and rewarding. You can kick off by incorporating more whole plant foods into your meals, and consider supplements if needed. Just remember to go slow, stay hydrated, and consult a healthcare provider if you have any concerns.

References:

[1] Mayo Clinic. (2021). Dietary fiber: Essential for a healthy diet. Retrieved from https://www.mayoclinic.org/dietary-fiber/art-20043983 

[2] U.S. Department of Agriculture. (2021). Dietary Guidelines for Americans, 2020-2025. Retrieved from https://www.dietaryguidelines.gov 

[3] National Institutes of Health. (2021). Fiber supplements: Safe to take every day? Retrieved from https://www.nih.gov/fiber-supplements