In the realm of gut health, fiber is full of main character energy. You’d be hard-pressed to find a gastroenterologist who doesn’t hype the nutrient for its poop-regulating powers and ability to work wonders on your microbiome, or the colony of bugs populating your bowels. The problem is, the vast majority of folks aren’t even close to hitting the recommended daily intake, which is between 25 and 38 grams (depending on your age and sex). So if you’re one of the many people who deal with GI troubles, constipation, or less-than-comfy poops, taking a fiber supplement might seem like an easy, foolproof solution for filling the gap and finding relief.
However, the truth is a bit more nuanced. Experts say there can be merit to padding your fiber supply with, say, a fiber powder or capsule, if largely because it’s hard to hit the recommendation with diet alone—especially if you’re not consuming plants, whole grains, and legumes in every meal and snack, Renee Korczak, PhD, RDN, an advanced practice registered dietitian nutritionist who specializes in gut health, tells SELF. After all, most foods aren’t exactly loaded with the stuff; whole grains are some of the richest sources (a cup of whole-wheat pasta has nine grams and the same amount of oatmeal has 10). But many popular fruits and veggies like apples, bananas, and carrots top out around just a few grams per serving, Joanne Slavin, PhD, RD, a professor in the Department of Food Science and Nutrition at the University of Minnesota – Twin Cities, tells SELF. It’s easy to see why even the best-laid plans to eat more fiber might fall short.
That said, not all fiber supplements are created equal, nor do they all share the full set of benefits you can get from chomping on the real stuff. Below, experts break down how and when a fiber supplement can add value, and the best tactics for working one into your life.
First, you should know that getting enough fiber from foods, specifically, is important for more than just keeping you regular.
Yes, fiber is essential for helping you form stools and pass them comfortably. But before you start pounding supplemental versions for poop-related reasons, you should know that the daily fiber guidelines aren’t actually based on its gut effects. These numbers come from research that found a link between a certain level of fiber intake and lower risk of heart disease. (That’s right: Your body’s metabolism of fiber can influence metrics like your cholesterol levels that impact your heart health—more on this below.) And crucially, the studies that identified this association involved people who were eating a bunch of fibrous foods. So it’s not clear that fiber plucked out of its natural source or synthetically derived and put into a supplement would even offer the same benefit. After all, most fiber-rich foods have a plethora of other nutritional gems, like antioxidants and protein, that could play a part in the heart-related upsides researchers have noted.
“Fiber consumption is more so a marker of a plant-based diet that brings other beneficial chemicals along, too,” Dr. Slavin explains. It’s the reason why the Dietary Guidelines specify loading up on fiber by way of fruits, veggies, and the like—and not purely by supplement.
Supplemental fiber can also function differently in your body than the naturally occurring form.
While there’s little to suggest that hitting your fiber goal mostly (or even partially) via supplements will offer you the same long-term heart protection as filling up on the real deal, you might wonder about the short-term potential of these pills and powders. Do they provide the same support in the, er, poop department and throughout your gut? It depends.
What unites all types of fiber (in a supplement or food) is an inability to get broken down and absorbed in your small intestine the way other carbs are; it slides through to your large intestine mostly unscathed, which is why it can keep you regular. But not all fiber supplements function quite the same way as the fiber in a whole food.
That's because fiber-rich foods naturally tend to have a mix of multiple fibers, which can be categorized into two types: soluble and insoluble. The former (e.g., pectin and beta-glucans) partially dissolves in your GI juices, thickening into a goo that slows the passage of food. This can temper the typical blood-sugar spike after a meal and reduce your body’s uptake of not-so-healthy cholesterol—which may help explain why fiber can protect you against heart disease, as well as type 2 diabetes. When this soluble fiber arrives in your colon, it can serve as a prebiotic, or a feast for your gut bugs, which then pump out beneficial chemicals. The latter insoluble type (e.g., cellulose and lignins), by contrast, stays intact as it chugs through your colon, acting as bulk that can make you feel more full and help you poop more easily.
Supplements, however, usually just contain a single fiber, and it’s often a soluble kind since these are easier to turn into edible products than the gummier insoluble types. (Same goes for packaged goods with added fiber, like cookies, cereals, and protein bars.) This fiber is either made synthetically or “isolated,” meaning that manufacturers extract the ingredient from a plant source (whereas the fibers naturally contained in foods are called “intact” or “intrinsic”). That leaves you with just one compound versus multiple that likely contribute to all the positive effects we expect from fiber-rich foods. In fact, the FDA just requires that each kind of fiber used in a supplement or added to food has “a beneficial physiological effect on human health,” which means there’s a lot of variety, Dr. Slavin says.
The right kind of fiber supplement for you depends on the effects you’re looking for.
Besides the solubility of an isolated fiber, research suggests characteristics like how viscous (a.k.a. gel-like) it is and whether it can be fermented by gut bacteria influence its effects. So which one you might choose to take depends on what outcome you’re after.
The kinds with a metabolic, heart-health-boosting benefit:
There’s the soluble types that both form a gooey gel and get broken down by your gut bugs, like beta-glucan (in oats and barley). Their viscosity allows for the cholesterol-lowering and blood-sugar-regulating effects noted above, and their fermentability could support your microbiome, too—though the latter isn’t something manufacturers can make a health claim around yet, Dr. Slavin notes. (Psyllium is also viscous and shares these heart-health benefits, but it isn’t fermented—more on this later.)
The kinds that might help your gut bugs flourish:
Then there’s the soluble kinds that don’t thicken into a gel but still get fermented—this includes fibers like inulin (Fiber Choice) that are added to drinks since they tend to be less sticky, as well as wheat dextrin (Benefiber) and partially hydrolyzed guar gum (Sunfiber). These don’t share the above heart-specific benefits; Dr. Slavin points out that inulin, for example, scored its FDA designation because it increases calcium absorption, which is a cool thing but also probably not why you’d reach for it. They do have a prebiotic effect, though, which may help your good gut bugs thrive (but again, there’s no official claim around that).
The kinds that just make you poop, STAT:
There’s also the rarer insoluble fiber supplements, which don’t dissolve, form a gel, or get fermented, like calcium polycarbophil (FiberCon) and wheat bran. These mostly have a laxative effect, prompting your gut to release more liquid and bulking up poop to move it through you. Same goes for methylcellulose (Citrucel), which is technically a soluble fiber but doesn’t form a gel nor get fermented; it just adds volume to keep poop chugging along.
The combination fiber with a bunch of benefits for both your heart and gut:
And then there’s psyllium (Metamucil, Konsyl), which is in a category of its own: It’s mainly soluble and gel-forming, so it can lower cholesterol and control blood sugar, but it also contains some insoluble fiber and does not typically get fermented. This combination creates a unique poop-normalizing effect, meaning it can help with both constipation and diarrhea. Like insoluble fibers, it doesn’t get broken down in your gut and it draws water into your stool, creating easier-to-pass poops—but its tendency to clump up into a gel can also firm liquid-y poops in diarrhea and help reduce frequency and urgency, Amy Bragagnini, MS, RD, clinical oncology dietitian at Trinity Health Lacks Cancer Center, in Grand Rapids, Michigan, and spokesperson for the Academy of Nutrition and Dietetics, tells SELF. So basically, it’s a catchall fiber supplement—the one that Anish A. Sheth, MD, a gastroenterologist at Penn Medicine and chief of gastroenterology at Princeton Medical Center, tells SELF he recommends regularly to his patients above all other types.
Whichever kind you choose, be sure to scan the ingredients list for what’s included beyond the fiber. You’ll want to steer clear of supplements with a lot of artificial sweeteners or added sugar (common in gummy and wafer versions), Bragagnini says, as both could be counterproductive for your gut. And also note that certain options may contain gluten (for instance, ones with wheat dextrin or wheat bran), so keep an eye out if you have Celiac or are gluten-sensitive.
You might need to avoid fiber supplements if you have certain health conditions or are on medication.
Fiber is tricky territory for some people, including folks with a functional GI condition like irritable bowel syndrome (IBS). Fermentable types of fiber (as well as high-fiber foods that get similarly broken down, for that matter) can worsen IBS symptoms, Dr. Sheth says. That’s because your gut bugs pump out gas as a byproduct of fermentation, he notes, which may trigger bloating and distention (a puffed-out belly). Research suggests our microbes really chow down on inulin, so that one may especially cause gas and discomfort in sensitive folks.
On the flip side, supplementing with psyllium has been shown to improve IBS symptoms, by way of its poop-regulating effect. And in people whose IBS manifests as constipation (IBS-C), insoluble fibers like wheat bran could help get things going and alleviate symptoms. All to say, if you have IBS, it’s essential to chat with your doc to figure out whether you should take a fiber supplement, and if so, which type.
The fiber effect may be similarly case-dependent for people with an inflammatory bowel disease (IBD) like Crohn’s or ulcerative colitis. Some research suggests that the laxative aspect of certain fibers (say, insoluble types) could worsen symptoms like diarrhea. And people with IBD who’ve had blockages in their small intestine or surgery for strictures (a narrowing of the intestine caused by scar tissue) should steer clear of excess fiber, given that bulkier stool can trigger a bowel obstruction in these cases, Dr. Sheth says. Yet, other research points to potential benefits of fiber in IBD: Fermentable types may prompt the growth of healthy gut bacteria that in turn release anti-inflammatory compounds and improve symptoms. Hence the importance of asking your doctor first here, too.
The same goes if you’re currently on any medications and plan to work a fiber supplement into your routine. Generally, fiber can slow down or reduce your absorption of meds as it trudges through your system, Bragagnini says, so you may need to space out when you’re taking each. Interactions commonly occur with antidepressants, diabetes drugs, and cholesterol-lowering medications—but again, it’s best to check first if you take anything.
If you’re introducing a fiber supplement, do so gradually and with lots of water.
You might struggle to get enough fiber from food alone—but with supplements, it’s all too easy to go overboard. For reference, one teaspoon of psyllium powder contains 3.4 grams of fiber, which is equivalent to eating a whole apple. Fiber gummies and wafers can be even more concentrated, and their yummy taste can make it tempting to pop a few extra beyond the recommended serving. “The number-one misconception about fiber is that if a little is good, more is better,” Bragagnini says. When you’re ramping up your intake, particularly with supplemental forms, you really want to go “low and slow,” Dr. Korczak says.
Start with a single dose of the fiber supplement you choose (as indicated on the package) per day—which is typically about two to four grams of fiber, Bragagnini says. Powders require you to mix each serving into eight ounces of water, but regardless of the type you take, be sure to increase your water intake. Fiber binds to liquid in your GI tract; if you consume more of it without being adequately hydrated, you could wind up constipated, Dr. Sheth says.
At the start of your fiber journey, you might also notice some mild GI upset, like gas and bloating, Dr. Korczak says, but that usually settles down within a week to 10 days. After giving yourself at least that long to adjust, if you’re no longer dealing with any tummy troubles, you can increase your intake (though Bragagnini suggests taking in no more than 10 grams of fiber from a supplement total per day). As you build up, Dr. Korczak also recommends jotting down any symptoms you experience each day along with the dose you’re taking to determine what amount feels most tolerable to you.
As Dr. Slavin points out, we all have unique GI systems and can respond differently to distinct types of fiber. So it’s also possible that certain kinds just don’t sit well with you or continue to send your gut into a tizzy even after you’ve been taking them for several days. In that scenario, switching types might resolve your issues. Though, if you’re dealing with constant GI troubles and worried your fiber intake is to blame, it’s smart to consult with a registered dietitian who can assess your situation before playing fiber whack-a-mole.
And remember, even if you can tolerate a fiber supplement with zero issues, it should remain just that: a supplement or companion to the fiber you’re getting from whole foods, not a replacement for it, Bragagnini says. Yes, you might experience some real benefits from consuming an isolated fiber—but the blend of intrinsic fibers and other supportive nutrients found in whole foods will always give you more bang for your buck.
Related:
- 5 Little Things GI Docs Do Each Day for Better Gut Health
- Supplements That Promise to Make You Prettier, Healthier, Better Are Everywhere. Here’s What the Science Says
- What Is Coconut Kefir, and Can It Really Do Anything for Your Gut Health?
Get more of SELF's great service journalism delivered right to your inbox.
