What to Know Before You Take Fiber Supplements

Not all fiber supplements are created equally, so how do you know which one to choose? Fiber supplements may be prescribed for both diarrhea and constipation. If that seems strange, it won't after some explanation of how fiber works. Fiber will bulk up the stool, making it firmer if it's too loose. It will also help if the stool is too hard, by making it easier to pass. The goal is to have a bowel movement that is soft but not liquid, which passes easily, without feeling the need to strain.

There are three main types of soluble fiber supplements that are sold over-the-counter: psyllium, methylcellulose, and polycarbophil. Each of these types of fiber has varying uses, side effects, and properties. Talk with your doctor about fiber supplements to decide which is best for your body. When shopping for fiber, look closely at the ingredients to discover which form of fiber is used in each commercial brand.

Also be aware of additives in your fiber supplement, you probably don't need added sugars, flavorings, or colors. If you're just starting with a fiber supplement, use a low dose and drink plenty of water when you take it. Increase the dose slowly until bowel movements are soft and easy to pass.

Brand names: Metamucil, Fiberall, Hydrocil, Konsyl, Perdiem, Serutan

Psyllium is a fiber supplement that can be taken every day to bulk up the stool, which makes it easier to pass. Psyllium works by breaking down in the gut and becoming a food source for the "good bacteria" that live there. Psyllium is used for treating constipation, irritable bowel syndrome (IBS) and diverticulosis. In addition, psyllium may lower cholesterol levels by 10% to 15% in some people, which is an added benefit for those who have been told that their cholesterol is high. On the downside, psyllium does contain calories and may cause some people to have intestinal gas.

Brand name: Citrucel

Methylcellulose is a fiber that is non-allergenic, non-fermentable, can be taken every day, and is created from the cell wall of plants. It is not absorbed by the intestinal tract but instead absorbs 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 other types of fiber supplements to cause intestinal gas. It is absorbed by cold water and forms a gel, and should be taken 2 hours before or after taking other medications.

Brand names: Fibercon, Fiber-Lax, Equalactin, Mitrolan

Similar to methylcellulose, polycarbophil is created from plants and is not absorbed by the body. Polycarbophil absorbs water in the intestinal tract and creates a bulkier and softer stool. Polycarbophil is a type of fiber that is less likely to cause bloating and it can be used long term. It may be used to treat constipation, IBS, and diverticulosis. This form of fiber is not appropriate for people who have difficulty swallowing. It should be taken about 2 hours before or after taking other medications, in order to avoid interfering with absorption.

All these forms of fiber are available over-the-counter and are generally safe to use. However, those that are considering taking a fiber supplement every day to treat a medical condition (either for a bowel problem or for high cholesterol), should talk to a doctor first. This is to ensure that the type of fiber chosen is the one that will work most effectively and to ensure the correct dose. In addition, people that are experiencing diarrhea or constipation on a regular basis may need to be evaluated for a digestive condition before starting to treat the problem with fiber.