The Health Benefits of Fiber Supplements

Help with Constipation, Diarrhea, IBS, IBD, and Diverticulosis

Psyllium Pills

Roel Smart/E+/Getty Images

Dietary fiber is a plant-based nutrient that's necessary for the healthy functioning of your digestive system. In addition to helping your bowels stay regular, it's also useful for maintaining optimum cholesterol ad blood sugar levels as well as a healthy weight. Although it's technically a carbohydrate, it's not the kind that can be broken down into digestible sugars by the body. Instead, fiber travels through your digestive system while bulking and softening your stool—making it easier to pass. It also helps absorb excess blood sugars and cholesterols.

The American Dietetic Association recommends 38 grams (g) of fiber a day for men, and 25g a day for women.

Fiber is found in fruits, vegetables, legumes, and whole grains, and is an important part of the diet. But because many people find it difficult to eat the recommended quantity of 25 to 38 g per day, fiber supplementation can be extremely helpful to ease the symptoms of a variety of digestive discomforts like diarrhea and constipation. Today, many fiber supplements are found on the market containing one of three active ingredients: psyllium, methylcellulose, and polycarbophil.

Health Benefits

If you have diarrhea, supplementing with fiber can bulk up the stool and reduce frequent urges to evacuate the bowel. If you have constipation, fiber supplements can soften your stool and speed up its movement through the colon. To understand how fiber helps relieve symptoms of both diarrhea and constipation, it's important to differentiate between soluble fiber and insoluble fiber. Soluble fiber forms a gel in your colon by absorbing water and retaining it in your stool, which makes bowel movements softer and easier to pass. Insoluble fiber bulks stool up, which also helps it move through your intestines more easily. Thus, fiber can also help you avoid hemorrhoids and anal fissures that can develop when straining to pass a bowel movement.

Additionally, supplementing with fiber can be part of a treatment plan for conditions such as irritable bowel syndrome (IBS), various types of inflammatory bowel disease (IBD) like Crohn's disease and ulcerative colitis, as well as diverticulosis. However, because research continues into the types and quantities of fiber that are useful in treating these conditions, it's important to consult your doctor about the correct fiber supplementation and dosage.

Fiber increases satiety, or fullness, and is thus helpful for those looking to lose weight or maintain a healthy weight. Sufficient fiber intake has also been shown to decrease the risk of certain cancers, heart disease, and diabetes. There is also evidence that enough fiber, when combined with a diet rich in Vitamin A, has a protective effect against food allergies.

Possible Side Effects

The potential side effects of fiber supplementation include:

  • Gas and gas pain
  • Abdominal bloating
  • Lowered blood sugar
  • Diarrhea or constipation (if taken in excess)
  • Weight loss
  • Lessened effectiveness of medications and vitamins (if taken at the same time as fiber)

Because of the way fiber supplements bulk up in the intestinal tract and absorb surrounding materials, they can interfere with the body's ability to assimilate medications, vitamins, and nutrients. For that reason, it's important to consume fiber supplements at least one hour after, or two hours before, taking medications and important vitamins.

Dosage and Preparation

Fiber supplements often come in the form of powders meant to be mixed with water or another liquid. They also are available in capsule form, or as additives to foods like crackers, cookies, cereals, and bars. Dosage will vary based on the product and your desired effects. If you are healthy, it's generally recommended to start with a low dose of fiber and build up until you've reached optimum total daily fiber intake—roughly 25g for women and 38g for men—which should also include your dietary sources of fiber. If you're using fiber supplements to treat a condition like IBS or IBD, consult your doctor about the proper dosage.

What to Look For

When shopping for fiber, look closely at the ingredients to discover which form of fiber is used in each commercial brand. Also, if you're avoiding added sugar, salt, flavorings, or dyes, check the label for these common additives. If you're just starting with a fiber supplement, use a low dose and drink plenty of water when you take the supplement and throughout the day. Increase the dose slowly until you reach either the desired total intake or a specific effect.


Psyllium is made from the seeds of a plant in the Plantago genus and contains about 70% soluble fiber and 30% insoluble fiber. It helps the stool absorb water and bulks it up, making it easier to pass. It also breaks down in the gut (a process called fermentation) and becomes a food source for the "good bacteria" that reside there. Psyllium is used for treating constipation, irritable bowel syndrome (IBS), and diverticulosis.

In addition, psyllium may lower cholesterol levels and provide some protection from heart disease. On the downside, psyllium may cause intestinal gas and contains a small number of calories (roughly 20 calories per tablespoon).

Psyllium is sold under the brand names Metamucil, Fiberall, Hydrocil, Konsyl, Perdiem, and Serutan.


Methylcellulose is a non-allergenic and non-fermentable fiber created from the cell walls of plants. Instead of being absorbed by the intestinal tract, methylcellulose pulls in water to create a softer stool. Methylcellulose is often used to treat constipation, diverticulosis, IBS, and some causes of diarrhea.

Because it does not ferment, it is less likely than psyllium to cause intestinal gas; however, methylcellulose does not feed healthy gut bacteria the way psyllium does. It can be used longterm but it should be noted that, because it can interfere with absorption, methylcellulose should be taken apart from any prescribed medications.

Methylcellulose is sold under the brand name Citrucel.


Similar to methylcellulose, polycarbophil absorbs water in the intestinal tract and creates a bulkier and softer stool. Because it does not ferment and is not absorbed by the body, polycarbophil is less likely to cause bloating and can, therefore, be comfortably used long term.

Polycarbophil may be used to treat constipation, IBS, and diverticulosis, but is not appropriate for people who have difficulty swallowing. Like methylcellulose, it should be taken about two hours apart from medications.

Polycarbophil is sold under the brand names Fibercon, Fiber-Lax, Equalactin, and Mitrolan.

Other Questions

What are the best dietary sources of fiber?

Whether or not you choose to supplement with fiber, it's still important to include a variety of high-fiber foods in your diet, such as:

  • Fresh fruit (pears, apples, strawberries, bananas)
  • Fresh vegetables (broccoli, Brussel sprouts, beets, and carrots)
  • Legumes (lentils, split peas, kidney beans, chickpeas, black beans, pinto beans)
  • Whole Grains (quinoa, oats, brown rice, millet, barley)
  • Other food sources of fiber (popcorn, sweet potatoes, and chia)

Is it a good idea to take fiber supplements every day?

There is currently no evidence to suggest that taking daily fiber supplements is harmful, and many people do make it part of their everyday health regimen.

What time of day is best?

Different manufacturers may have varying recommendations on when and how frequently to take fiber supplements. You may want to divide your daily dose into two or three portions to reduce bloating and gas that could occur when taking a large dose all at once. To avoid malabsorption, it's important to take medications or vitamins either one hour before, or two hours after, taking fiber supplements. If using a powdered form of fiber, be sure to dissolve it well. No matter what kind of fiber supplement you are using, be sure to drink plenty of water.

A Word from VeryWell

Fiber supplements are available over-the-counter and are generally considered safe to use. However, if you're considering taking a fiber supplement to treat a medical condition, talk to a doctor first to ensure that you're taking the most effective product in the right dose. If you are experiencing diarrhea or constipation regularly, you may need to be evaluated for a digestive condition before starting to treat with fiber.

Was this page helpful?
Article 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. 10.4103/2231-4040.93561

  2. 10.1016/j.jcm.2017.05.005

  3. 10.1016/j.jcm.2017.11.002


  5. 10.1093/ajcn/71.2.472

  6. 10.4162/nrp.2019.13.3.205

Additional Reading