Benefiber and Metamucil are two popular dietary supplements to relieve constipation and other digestive issues. Each one may cause different side effects.

Benefiber and Metamucil are fiber supplements designed to relieve constipation. The two brands work in very similar ways, but they may have slightly different effects on the body.

This article looks at the similarities and differences between Benefiber and Metamucil for constipation and other medical conditions, and alternative products, such as Miralax and Citrucel.

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Benefiber and Metamucil are both over-the-counter (OTC) soluble fiber supplements. They work in a very similar way to help relieve constipation and support gut health.

Both products contain a high concentration of fiber. Fiber makes a person’s stools bulkier and softer, which results in more comfortable and frequent bowel movements.

The main difference between Benefiber and Metamucil is the type of fiber they contain:

  • Benefiber contains wheat dextrin, which is a form of wheat starch.
  • Metamucil contains psyllium husk powder. Psyllium is a type of fiber made from the husks of psyllium seeds.

Benefiber and Metamucil may also cause different effects in the body.

Metamucil may improve cholesterol

The Metamucil label says that it can improve people’s cholesterol levels and help them maintain healthy blood sugar levels. This is because it contains psyllium.

An older study from 2010 tested the effects of Metamucil on 72 people who were overweight or obese. They found that adding this fiber supplement improved cholesterol and insulin levels.

The researchers recommend eating a healthful, fiber-rich diet in addition to taking fiber supplements. It is unclear whether Benefiber would have similar effects.

Learn more about a high fiber diet.

Benefiber contains traces of gluten

Benefiber contains wheat, but the manufacturers consider it gluten-free because it contains less than 20 parts per million (ppm) of gluten. However, they say that people with gluten intolerance or celiac disease should not use Benefiber unless directed by a healthcare professional.

Learn more about gluten.

Benefiber may be a more natural choice

Benefiber contains fewer additional ingredients than Metamucil. Benefiber contains only wheat germ, which may make it a more natural choice.

There is also a more natural version of Metamucil available, though the familiar orange-flavored forms of Metamucil often contain sweeteners, colorants, and other additives, which may make it more pleasant to drink.

Fiber is an important part of a person’s diet. People can increase their fiber by eating more high fiber foods or introducing fiber supplements.

Both Benefiber and Metamucil can have the following benefits.

Improving gut health

Keeping the bowels moving regularly can improve gut health and relieve the symptoms of digestive conditions, such as irritable bowel syndrome (IBS) and diverticulosis.

The soluble fiber in Benefiber and Metamucil can feed the good bacteria in the intestines.

Heart health

The manufacturers of fiber supplements, such as Benefiber and Metamucil, state that they are heart-healthy products. This is because of the benefits a high fiber diet can have on a person’s heart health.

A 2017 review found that higher fiber intake might lower the risk of cardiovascular disease.

Weight loss

Some weight loss products, programs, and healthcare professionals recommend consuming fiber as a way to make the body feel fuller for longer. This may decrease a person’s appetite and help with weight loss.

However, OTC fiber supplements, such as Metamucil or Benefiber, are not approved as weight loss products and are not likely to have a direct impact on weight loss.

Both Benefiber and Metamucil have specific instructions regarding dosage. The dosage is higher for Metamucil than Benefiber.

Stir the recommended dosage into 4–8 ounces of liquid, making sure the powder dissolves thoroughly before drinking.

The powdered version of both products mixes well in cool or room temperature liquids, including smoothies, protein shakes, water, juice, or milk.

People who do not get much fiber in their diet should introduce these supplements slowly to avoid side effects. Gradually increase the number of servings from 1 to 3 per day while judging how the body reacts to the product.

Some healthcare professionals will also recommend drinking more liquid with the supplements, as they absorb a lot of water.

Metamucil is also available in capsule and wafer form. This makes taking the supplement more convenient as people can swallow the supplement with a large glass of water.

People should speak with a healthcare professional before taking fiber supplements during pregnancy.

The recommended dosages differ depending on a person’s age:

  • Adult doses of both Benefiber and Metamucil are suitable for children over 12.
  • Children ages 6 -11 should take half the adult dose of Benefiber.
  • Consult a healthcare professional before giving Metamucil to children under 12.
  • Ask a healthcare professional before giving fiber supplements to children under 6.

Increasing dietary fiber with either Metamucil or Benefiber may cause a few side effects or risks.

Stomach issues

Some people might experience gas or stomach cramps while taking these supplements, though the symptoms may go away as the body gets used to the supplement. If this happens, reduce the dosage or drink extra water while taking the supplement.

Allergic reactions

People who are sensitive to or allergic to psyllium should avoid Metamucil. People who are sensitive to gluten should avoid Benefiber. Anyone experiencing an allergic reaction while taking these products should stop taking them and contact a healthcare professional.

Medical conditions

People with certain stomach conditions may need to avoid both Benefiber and Metamucil. Anyone with stomach or digestive disorders should speak with a healthcare professional before taking either of these supplements.

Anyone experiencing constipation for a week or more should stop taking dietary fiber supplements, such as Benefiber or Metamucil, and contact a healthcare professional.

Drug interactions

Both Benefiber and Metamucil might adversely affect how well the body absorbs certain medications, making them less effective.

Anyone taking regular medication should consult a healthcare professional or pharmacist before using these supplements.

Benefiber and Metamucil are not the only name-brand supplements to relieve constipation on the market, and some people may find they prefer other brands.

Two popular alternatives are Citrucel and Miralax. Miralax is not a fiber-based supplement.


Citrucel is a fiber supplement that contains methylcellulose, which comes from plant matter. It is a non-allergenic form of soluble fiber that may not cause as much gas buildup as some other products.

People with sensitivities or who experience side effects when taking other constipation relief supplements may find that Citrucel is a good alternative.


Miralax is not a fiber-based supplement. The active ingredient is polyethylene glycol, which pulls water into the stool to help relieve constipation.

As it is not a fiber supplement, Miralax does not offer the same additional potential benefits as other brands.

Dietary fiber

Benefiber and Metamucil are fiber supplements. People can also increase their daily fiber intake by including more fiber-rich foods in their diets.

Fiber-rich foods include:

  • grains, such as barley and oat bran
  • vegetables, such as beans, lentils, and sweet potatoes
  • fruit, such as blackberries, pears, and oranges
  • proteins, such as almonds, chestnuts, and sunflower seeds

Both Benefiber and Metamucil are soluble fiber supplements used to treat occasional constipation that may have other helpful benefits in the body.

These supplements have slight differences but perform essentially the same function. In most cases, the choice between them is personal preference.