Yes, Citrucel is a soluble fiber supplement. Its active ingredient is methylcellulose, a chemically modified plant fiber classified as a low-viscosity soluble fiber. But the way it behaves in your gut is distinct from many other soluble fibers, which is why Citrucel markets itself as the “less gas” option and why the distinction matters if you’re choosing between supplements.
What Makes Citrucel Different From Other Soluble Fibers
Not all soluble fibers work the same way. Soluble fiber dissolves in water, but what happens after that varies a lot depending on the specific type. Citrucel’s methylcellulose is soluble and viscous, meaning it thickens when mixed with water. However, it does not form a true gel the way psyllium (the fiber in Metamucil) does. This distinction has real consequences for your body.
Gel-forming soluble fibers like psyllium have been shown to improve blood sugar control and lower cholesterol. Methylcellulose, because it’s viscous but non-gel-forming, does not significantly lower cholesterol. So if you’re taking a fiber supplement specifically for heart health or blood sugar management, Citrucel isn’t the best fit. If your main goal is relieving constipation with fewer digestive side effects, it may be a better choice.
Why Citrucel Produces Less Gas
The biggest selling point of Citrucel is reduced gas and flatulence compared to many other fiber supplements. This comes down to fermentation. When bacteria in your colon break down fiber, they produce gas as a byproduct. Many popular fibers, including wheat dextrin (Benefiber), inulin, and beta-glucan (found in oats), are readily fermented. Once fermented, the fiber is no longer present in your stool, and you’re left with gas and short-chain fatty acids instead of bulk.
Methylcellulose is classified as a nonfermentable fiber. A study published in the Annals of Internal Medicine tested this directly: participants taking methylcellulose showed no increase in breath hydrogen concentration (a marker of gas production in the colon) compared to baseline. In fact, hydrogen levels steadily declined over the 12-hour measurement period. Flatulence frequency did not increase either.
That said, participants did report feeling more bloated while taking methylcellulose. The researchers attributed this not to gas production but to the increased bulk in the intestines. Methylcellulose holds onto water, which makes stool larger and heavier. That fullness in the bowel can feel like bloating even when actual gas levels haven’t changed. So “less gas” is accurate, but “zero digestive awareness” would be an overstatement.
How Well It Works for Constipation
Citrucel is marketed and approved as an over-the-counter laxative for constipation relief. It works by drawing water into the stool, making it softer and easier to pass. The mechanism is straightforward and similar to how psyllium works.
Here’s the caveat: there are no well-controlled clinical studies in constipated patients demonstrating that methylcellulose is effective versus placebo. The American College of Gastroenterology reviewed the evidence and determined there was insufficient clinical data to recommend methylcellulose for treating chronic constipation. Psyllium, by contrast, has stronger clinical backing. This doesn’t mean Citrucel doesn’t work for many people. It means the formal evidence base is thinner than what exists for its main competitor.
How to Take It Properly
Citrucel comes in both powder and caplet forms. For the powder, the standard adult starting dose is one heaping tablespoon (or one rounded tablespoon for the sugar-free version), which you can increase up to three times per day as needed. For caplets, the typical dose is two caplets up to six times daily, with a maximum of 12 caplets per day.
The most important rule: every dose needs to be taken with at least 8 full ounces of water. This isn’t optional. Methylcellulose swells when it absorbs liquid, and without enough fluid, it can expand in your throat or esophagus and cause choking. If you have any difficulty swallowing, this product is not appropriate for you. The same water requirement applies to caplets, not just the powder form.
How It Fits Into Your Total Fiber Intake
The Dietary Guidelines for Americans recommend 14 grams of fiber per 1,000 calories consumed. For most adults, that works out to roughly 25 to 30 grams per day. Most Americans fall well short of that target, which is why fiber is considered a nutrient of public health concern.
A single dose of Citrucel powder provides about 2 grams of fiber. Even at the maximum of three doses per day, you’re getting 6 grams, which is a helpful supplement to a fiber-rich diet but not a replacement for one. Whole foods like beans, lentils, vegetables, fruits, and whole grains deliver a mix of soluble and insoluble fibers along with vitamins and minerals that a supplement can’t replicate. Think of Citrucel as filling a gap, not as your primary fiber source.
Citrucel vs. Psyllium: Choosing Between Them
The two most common fiber supplements on store shelves are Citrucel (methylcellulose) and Metamucil (psyllium). Both are soluble, both resist fermentation, and both work by holding water in the stool. The differences come down to what else each one does and how your body tolerates them.
Psyllium forms a viscous gel that traps bile acids and slows glucose absorption. This gives it proven benefits for cholesterol reduction and blood sugar control that methylcellulose lacks. On the other hand, psyllium’s gel-forming nature can make it feel thicker and less pleasant to drink, and some people find it causes more initial digestive discomfort as they adjust.
If your priority is cardiovascular or metabolic health alongside regularity, psyllium has the stronger evidence. If your primary concern is constipation and you’re sensitive to digestive side effects, methylcellulose is a reasonable alternative, keeping in mind that its clinical evidence for constipation is less robust. Starting with a low dose of either product and increasing gradually gives your gut time to adapt.