Benefiber vs. Metamucil

Let's face it — most of us aren't getting enough fiber. In fact, over 90 percent of people fall short of the daily recommendation, according to the USDA's Dietary Guidelines for Americans. (In case you're wondering, it's 14 grams of fiber per 1,000 calories, so around 28 grams for a 2,000-calorie diet).

While whole foods like fruits, veggies, and grains should be your main source of fiber, supplements like Benefiber and Metamucil can help fill in the gaps. These two popular options are both soluble fibers (i.e., they dissolve in water), but they work differently in your body.

So, in a head-to-head comparison of Benefiber vs. Metamucil, which one's right for you? Let's break it down.

Benefiber's active ingredient, wheat dextrin, is a non-viscous soluble fiber, meaning it doesn't form a gel with water. While it's not great for improving bowel function, it's fully fermentable and works as a prebiotic to nourish gut bacteria, says registered dietitian Amanda Holtzer, RD.

Metamucil, on the other hand, contains psyllium husk, a viscous soluble fiber extracted from the seeds of the ‌Plantago ovata‌ plant, according to Tufts University. When mixed with water, psyllium forms a gel in your intestines, triggering muscle contractions (peristalsis) that move stool through your digestive tract, Holtzer says. This makes it the go-to fiber for relieving constipation and keeping things regular.

The psyllium in Metamucil works its magic by absorbing water in the gut and forming a gel-like substance, which regulates stool texture and promotes regularity, Holtzer says. Whether you're dealing with constipation or diarrhea, psyllium can soften hard stools or firm up loose ones, according to Tufts University.

On the other hand, the wheat dextrin in Benefiber doesn't form a gel, so it's not effective for constipation or diarrhea. However, as a prebiotic, it feeds your gut microbiota, Holzer says. The downside? This fermentation process can cause bloating and gas.

Fiber is a carb our bodies can't digest, so it doesn't break down into glucose or spike blood sugar, Holtzer says. That's why high-fiber carbs help keep blood sugar steady. Metamucil's psyllium husk, in particular, has been shown to improve blood sugar control, especially in people with type 2 diabetes. An October 2016 study in the ‌Nutrition Journal‌ found that taking 10.5 grams of psyllium daily (split into multiple doses) lowered fasting blood sugar and A1c levels over eight weeks.

Meanwhile, Benefiber's wheat dextrin lacks solid evidence for helping to manage blood sugar.

Psyllium fiber in Metamucil can help lower cholesterol by binding to cholesterol particles in the small intestine, keeping them out of your bloodstream and sending them out with your poop, Holtzer says. The science backs it up: an April 2017 review in the ‌Journal of the American Association of Nurse Practitioners‌ credits the way psyllium acts in the digestive tract and its gel-like properties for its cholesterol-lowering effects.

The jury's still out when it comes to whether Benefiber's wheat dextrin can help lower cholesterol levels and improve heart health. A June 2022 review in the ​‌Journal of Functional Foods​‌ concluded that resistant starch (like wheat dextrin) may have a positive effect on blood lipids, but the research is still inconclusive, and more studies are needed.

An August 2023 review in the ‌Journal of the American Association of Nurse Practitioners‌ found that taking 10.8 grams of psyllium daily before meals helped people with obesity and overweight lose weight over nearly five months. Psyllium's gel-like properties likely curb appetite by keeping you feeling fuller longer.

Wheat dextrin may also boost fullness, according to a small June 2021 ‌European Journal of Nutrition‌ study, but research on its weight-loss effects is mixed, with other studies showing no impact.

While Benefiber and Metamucil are safe for most people, check with your doctor or dietitian before starting a new supplement to rule out any issues (more on that later). If you're good to go, here's the breakdown:

• ‌Benefiber dosage‌: 2 teaspoons (stirred into water) up to 3 times daily for ages 12 and up.
• ‌Metamucil dosage‌: 1 tablespoon of psyllium husk mixed with water once a day.

A few tips before you start:

‌Go slowly‌. Adding too much fiber can have unwanted side effects (like bloating and gas). To avoid this, add a little at a time. For example, with Metamucil, start with 1 teaspoon three to four times per week, Holtzer says. If well tolerated, increase incrementally from there.

‌Don't take more than the standard dose.‌ Again, you don't want tummy troubles. Plus, taking more than 50 grams of fiber in a supplement per day can disrupt how your body absorbs nutrients, according to the Mayo Clinic‌.‌

‌Ask your provider‌. If you're unsure how much fiber to supplement, chat with your doctor. They can help you determine the right amount for you.

‌Get most of your fiber from food.‌ While Benefiber and Metamucil are safe to take long term, remember: they are only meant to supplement (i.e., fill in the gaps) of a healthy diet, Holtzer says. Aim to get the bulk of your fiber from whole foods such as fruits, vegetables, beans, legumes, and whole grains.

Benefiber and Metamucil are generally safe for regular use, but like any supplement, they come with potential risks and side effects, says Holtzer.

Taking too much Benefiber or Metamucil can cause GI discomfort. Possible symptoms to look out for include, per Holtzer:

• Excess bloat
• Gas
• Abdominal cramping
• Diarrhea
• Constipation

While Benefiber and Metamucil are generally safe, they might pose health risks to some groups. For people with certain health conditions, fiber supplements can trigger or worsen symptoms. Stay away from fiber supplements or consult your doctor if, per Holtzer and Tufts University:

• You have difficulty swallowing (psyllium husk can pose a choking threat)
• You have a history of severe, long-lasting constipation or fecal impactions, i.e., when poop gets stuck inside your rectum (excess fiber can increase your risk of intestinal blockages)
• You have Celiac disease or gluten intolerance (wheat dextrin may contain gluten)

Fiber supplements can mess with how your body absorbs certain medications, says Holtzer. These include drugs for thyroid issues, depression, diabetes, high cholesterol, heart problems, and seizures, plus common meds like aspirin, ibuprofen, and penicillin, per the Mayo Clinic. To play it safe, wait a couple of hours between taking your fiber supplement and your meds.

It all comes down to your goals, Holtzer says. If you're looking to lower LDL cholesterol, control your blood sugar, and keep things moving in the bathroom, Metamucil's psyllium husk is the way to go. If you want to nourish your gut microbiota, Benefiber's wheat dextrin has you covered. Either way, it's smart to check with your doctor or dietitian to make sure your pick works for your health needs and won't interfere with any meds.