The Health Benefits of Fiber Supplements

Helps with Constipation, Diarrhea, IBS, and Diverticular Disease

Fiber supplements are nutritional products that are available over the counter at drugstores, health food stores, big box stores, and online. They come in a variety of formulations, including capsules, powders, and pills, and contain one of three types of fiber: psyllium, methylcellulose, or polycarbophil.

Fiber supplements are typically taken to maintain a healthy digestive system, prevent or treat constipation, or help lower cholesterol and blood sugar. While generally regarded as safe, they can cause side effects such as bloating or gas, particularly if overused or not taken as directed.

If you are considering taking a fiber supplement, this article will help you better understand the benefits, side effects, possible interactions, and appropriate dosing of each of the different supplement types.

Psyllium pills piled on each other
Roel Smart / E+ / Getty Images

Health Benefits of Fiber Supplement

Fiber is a type of carbohydrate that's naturally found in fruits, vegetables, legumes, and whole grains. Fiber is important for maintaining regular bowel movements and offers numerous other benefits that extend well beyond digestive health.

The bottom line is that most people in the United States do not eat enough fiber from the foods they eat due in part to the high consumption of processed and fast foods in the typical American diet. Fiber supplements are one option if you are falling beneath the U.S. government's recommendations for the daily consumption of fiber.

Recommended Adult Daily Intake of Dietary Fiber
Age Group  Female Male
19-30 29 grams/day 34 grams/day 
31-50 25 grams/day 31 grams/day
51 and over 22 grams/day 28 grams/day 
Office of Disease Prevention and Health Promotion. Dietary Guidelines for Americans 2020-2025.

Fiber supplements are not intended to replace fiber found naturally in food. But, if you are not getting enough—perhaps because you are getting older and are eating smaller meals—fiber supplements may be a reasonable option.

The potential benefits of fiber supplements include:

Possible Side Effects

Fiber supplements are generally regarded as not only safe but beneficial to one's health. With that aid, there are potential side effects you may experience, including:

  • Gas
  • Cramping
  • Bloating
  • Diarrhea or constipation if taken in excess
  • Reduction of blood sugar level (which may require you to adjust doses if you are taking diabetes medications)

Some of these side effects (like gas, cramping, and bloating) tend to subside as your body adapts to the increased fiber intake.

Possible Drug Interactions

Because of the ways fiber supplements increase bulk in the intestinal tract, they can potentially interfere with the absorption of certain medications or supplements, including:

  • Bile acid sequestrants like Questran (cholestyramine) or Colestid (colestipol)
  • Diabetes medications like Diabeta (glyburide) and Glucophage (metformin)
  • Tricyclic antidepressants like Elavil (amitriptyline) and Tofranil (imipramine)
  • Tegretol (carbamazepine), an anti-seizure drug

Drug interactions like these may or may not be significant. Even so, it is important to speak with a healthcare provider before starting fiber supplements to ensure they are safe and appropriate for you.

Dosage and Preparation

Fiber supplements come in a variety of formulations, including powders to be mixed with water or another liquid or capsules to be swallowed whole. Fiber is also often added to foods like crackers, cookies, cereals, and bars.

Dosage will vary based on the product and the desired effects. It's generally advisable to start with a low dose and build up until you've reached the recommended total daily fiber intake, which should always take into account your dietary sources of fiber.


Made from the seeds of a plant in the Plantago genus, psyllium contains 70% soluble fiber (which turns into a gel, helping soften stools) and 30% insoluble fiber (which adds bulk to stool and aids with normal digestion).

In the gut, psyllium undergoes fermentation to become a food source for the "good" bacteria. For this reason, psyllium can cause gas.

Psyllium can be effective in treating constipation and IBS. It has roughly 20 calories per tablespoon. Brand names include Metamucil, Fiberall, Hydrocil, Konsyl, and Serutan. Most are sold in powder form and mixed with 8 ounces of water.

A typical dosage of psyllium is 5 to 10 grams (g) with meals at least once daily


Methylcellulose is non-allergenic, non-fermentable fiber created from the cell walls of plants. It's a soluble fiber that pulls in water to create a softer stool. It is often used to maintain regular bowel movements and to treat constipation and some causes of diarrhea.

Methylcellulose is sold under the brand name Citrucel and is available both as a caplet and powder. Regular Citrucel has roughly 60 calories per dose, while Sugar-Free Citrucel has 24 calories per dose.

The recommended dosage of Citrucel is as follows:

  • Caplets: Two 500-milligram (mg) caplets up to six times per day, followed by an 8-ounce glass of water
  • Powder: A heaping tablespoon (roughly 2 grams) mixed with 8 ounces of water up to four times daily.


Polycarbophil is a soluble fiber that water in the intestinal tract and creates a bulkier, softer stool. It does not ferment and is not absorbed by the body. As such, there is less likely to be gas or bloating.

Polycarbophil may be used to treat constipation and bowel movement irregularities, but it is not appropriate for people who with dysphagia (difficulty swallowing).

Polycarbophil is sold under the brand names FiberCon, Fiber Lax, Equalactin, and Mitrolan. Most are around 10 calories per dose and come as either regular tablets or chewable tablets.

The typical dosage of polycarbophil is 625 mg per day, followed by an 8-ounce glass of water. For the treatment of acute constipation, you can take 1,250 mg up to four times per day with an 8-ounce glass of water

What to Look For

When shopping for fiber supplements, you'll want to make sure it contains the type of fiber you want. Some supplements also have added sugar, salt, flavorings, or dyes, which you may want to avoid. For these reasons, make sure to check the ingredients listed on the packaging before making your purchase.

Which Fiber Supplement Is Best?

There is no strong evidence that psyllium, methylcellulose, or polycarbophil is inherently "better" than the other options or that pills, powders, or capsules are more or less effective.

The choice of fiber supplement is ultimately a personal one, ideally made with input from your healthcare provider.


Fiber supplements can be used to add to the dietary fiber you get from food. They can help ensure regular bowel movements, treat acute bouts of constipation and help lower cholesterol and blood sugar. There is evidence that they can reduce the risk of heart disease and even colon cancer.

Fiber supplements contain either psyllium, methylcellulose, or polycarbophil. Each works slightly differently from the others with different doses but, as a group, they are generally regarded as safe for daily use. Side effects include gas, bloating, and cramping.

A Word From Verywell

Fiber supplements are available over the counter and are considered safe for most people. If you have a medical condition you think might improve by taking a fiber supplement, talk to your healthcare provider first. If you are experiencing diarrhea or constipation regularly, you may need to be evaluated for a digestive condition before starting to treat it with fiber.

Frequently Asked Questions

  • What foods are high in fiber?

    Among the richest sources of dietary fiber:

    • Cereal
    • Popcorn
    • Whole grains (especially bulgur, spelt, teff, barley, and oat bran)
    • Beans
    • Lentils
    • Vegetables (artichokes, canned pumpkin, cooked parsnips, winter squash, turnip greens)
    • Whole fruits and berries
    • Fresh vegetables (broccoli, Brussels sprouts, beets, and carrots)
    • Legumes (lentils, split peas, kidney beans, chickpeas, black beans, pinto beans)
    • Seeds (pumpkin, chia, sunflower, flax)
  • What's the best time of day to take a fiber supplement?

    Recommendations vary, but you may want to divide your dose into two or even three portions to take at evenly spaced intervals throughout the day. For example, the makers of Metamucil advise taking their product three times a day with meals. This can help prevent bloating and gas that sometimes occur as a result of taking a large dose all at once.

  • Is it OK to take a fiber supplement every day?

    For most healthy people, it is perfectly fine to take a daily fiber supplement and many people rely on them to make up for a lack of fiber in their diet. That said, it's always best to get nutrients from dietary sources, so if you need to boost your fiber intake, start by eating more fiber-rich foods.

  • Can I take a fiber supplement at the same time I take my other medications?

    In general, you should avoid taking your medications with your fiber supplements. Since a fiber supplement passes through the digestive system relatively quickly, a medication taken at the same time as a supplement can be excreted in your stool before your body has a chance to absorb it. Ask your healthcare provider about the ideal timing.

13 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. McRorie J. Evidence-based approach to fiber supplements and clinically meaningful health benefits, part 1Nutr Today. 2015;50(2):82-89. doi:10.1097/nt.0000000000000082

  2. Lyon M, Kacinik V. Is there a place for dietary fiber supplements in weight managementCurr Obes Rep. 2012;1(2):59-67. doi:10.1007/s13679-012-0016-9

  3. Office of Disease Prevention and Health Promotion. Food sources of dietary fiber. In: Dietary Guidelines for Americans 2020-2025.

  4. Jalanka J, Major G, Murray K et al. The effect of psyllium husk on intestinal microbiota in constipated patients and healthy controlsInt J Mol Sci. 2019;20(2):433. doi:10.3390/ijms20020433

  5. Liu L, Wang S, Liu J. Fiber consumption and all-cause, cardiovascular, and cancer mortalities: a systematic review and meta-analysis of cohort studies. Mol Nutr Food Res. 2015;59(1):139-46. doi:10.1002/mnfr.201400449

  6. Fiber capsules side effects.

  7. Academy of Nutrition and Dietetics. Fiber.

  8. Harvard Health Publishing. By the way doctor? Will a fiber supplement interfere with my medications?

  9. Bruma Jose M. Satiety effects of psyllium in healthy volunteersAppetite. 2016;105:27-36. doi:10.1016/j.appet.2016.04.041

  10. Metamucil. Metamucil FAQS.

  11. PubChem. Methylcellulose.

  12. Polycarbophil.

  13. University of California San Francisco. Increasing Fiber Intake.

By Amber J. Tresca
Amber J. Tresca is a freelance writer and speaker who covers digestive conditions, including IBD. She was diagnosed with ulcerative colitis at age 16.