The idea of padding your fiber intake with a little something more isn’t new—Americans have been stirring scoopfuls of Metamucil powder into water since the 1930s. What’s different now is finding extra fiber added into cookies, cereals, yogurt, granola bars, protein bars…pretty much any packaged snack you can think of.
First of all: Why? Second of all: Is this added stuff on par with the real deal? Here’s everything you need to know about added fiber.
Why added fiber is showing up in everything
Fiber is a type of indigestible carb found in plant foods, including fruits, vegetables, whole grains, nuts, beans, and legumes. It’s made of a bunch of sugar molecules bound together in a way that makes it hard for our bodies to break it down, the FDA explains. And it’s an important part of a healthy diet.
There are actually two main kinds of fiber, slightly different but equally awesome. Soluble fiber regulates the absorption of sugar and cholesterol into the bloodstream by slowing down digestion, according to the FDA. This helps keep blood sugar levels stable and LDL levels low, which could explain why fiber intake is linked to a reduced risk of chronic conditions like heart disease and type 2 diabetes. Insoluble fiber adds bulk to our stool and speeds up digestion, making it great for combating constipation and promoting intestinal regularity, per the FDA.
Despite its well-demonstrated health benefits, most of us are way underdoing it on the fiber front. The Dietary Guidelines advise aiming for about 14 grams of fiber per 1,000 calories in your diet, so the exact number varies with your recommended caloric intake. While those guidelines are rough and ideal intake varies from person to person (with factors like your activity level and digestive health playing into it, too), there’s no escaping the fact that the average American isn’t getting anywhere near enough fiber—just 16 grams a day, per the U.S. National Library of Medicine. (Fun fact: that’s about the amount a girl aged 4 to 8 should eat, according to the Dietary Guidelines.) Given that low fiber intake is associated with poor health outcomes, it’s been designated a “nutrient of public health concern” by the U.S. Departments of Health and Human Services (HHS) and of Agriculture (USDA).
While Americans have been turning to straight-up fiber supplements (i.e. functional fiber) for decades to help them close that fiber gap and treat or prevent constipation, adding extra fiber to everyday snack products “is a newer trend in food manufacturing,” Colleen Tewksbury, Ph.D., M.P.H., R.D., a senior research investigator and bariatric program manager at Penn Medicine and president-elect of the Pennsylvania Academy of Nutrition and Dietetics, tells SELF.
Basically, food companies know that as the “eat more fiber” message percolates, more shoppers are scanning nutrition labels for fiber amounts (or at least more likely to be enticed by claims about high fiber content on the front). And food scientists have developed new types of supplemental fibers that can be added to foods without really impacting their taste or texture, Tewksbury says. So it makes perfect sense that companies are packing products from chips to ice cream with added fiber.
What added fiber actually is
When we say added fiber (sometimes called isolated fiber), we’re talking about a whole bunch of different types of fibers that are incorporated into food products during manufacturing. “They are not naturally occurring in foods, they are added in to boost the fiber content,” Tewksbury says. Oftentimes, if it’s not called out on the packaging, you may only know there is added fiber in a food by reading the ingredients list (more on what words to look out for in a minute).
Added fibers can be naturally derived—so, extracted from foods that contain fiber, like fruit or chicory roots—or synthetically made by combining different compounds in a lab. And they all have slightly different structures and properties. (That’s the case with naturally occurring fibers, too, by the way).
With all these different, unfamiliar types of added fibers popping up in our food supply over the past few years, the FDA realized they needed to standardize their definition of dietary fiber so that consumers, food manufacturers, and regulators could all be on the same page.
In 2016, the FDA asked food manufacturers to make their best cases for various added fibers to be counted as dietary fiber on nutrition labels. Their task was to show the FDA enough evidence to convince them that the fiber has at least one “beneficial physiological effect to human health,” the agency explains—such as lowering blood glucose, lowering cholesterol levels, lowering blood pressure, increasing the frequency of bowel movements, increasing mineral absorption in the intestinal tract, or reducing caloric intake.
In 2018, after conducting a comprehensive review of the evidence, the FDA ruled on which ingredients met that burden of proof. Eight that made the cut: beta-glucan soluble fiber, psyllium husk (the stuff found in Metamucil), cellulose, guar gum, pectin, locust bean gum, hydroxypropylmethylcellulose, and cross linked phosphorylated RS4. The FDA also plans to add a number of other added fibers to that list, and is allowing manufacturers to include them in their dietary fiber count for now until the rules are finalized. These include mixed plant cell wall fibers (like sugar cane fiber and apple fiber) and inulin, which may be the most common added fiber you see right now, Tewksbury says. “It’s cheap, you can’t taste it, and it doesn’t clump, so it results in better final products,” she explains. You might notice it listed on ingredient labels as inulin, chicory root extract, chicory root, chicory root fiber, oligofructose, or other names, per the FDA.
Now, if you look at nutrition facts labels, the number of grams of dietary fiber listed may include naturally occurring fibers and any of those particular added fibers. For example, if a granola bar has 2 grams of naturally occurring fiber from oats and 1 gram of added fiber from psyllium husk, you’ll simply see 3 grams of fiber on the label.
How it stacks up against the real thing
On a cellular level, added fibers looks pretty similar to intrinsic fibers, so our bodies process—or, rather, don’t process—them in largely the same way, Tewksbury says. Whether they are found naturally in a food or added to it, our small intestines can’t break fibers down, so they get passed along to the large intestine, where some soluble fiber does get broken down by bacteria, per the FDA.
The real differences can be seen when we zoom out a little and look at the overall composition of many added-fiber foods. Typically, these are foods that don’t have a lot of other nutritional pros, says Tewksbury, so eating them instead of naturally fiber-rich foods (like fruit and whole grains) will leave you missing out on other important vitamins and nutrients.
That doesn’t make the addition of fiber pointless, of course. If you were going to have a tasty treat anyway and you choose one that tastes exactly the same and packs an extra fiber punch, you’re getting a two-for-one deal. And certainly, “If your diet does not include sufficient fiber, then added fiber in the form of functional fiber can help you reach the target,” Donald Ford, M.D., an internist at Cleveland Clinic, tells SELF.
This also brings us to the tricky business of discerning the health impacts over the long term of added-fiber foods. Many if not most of the studies in the FDA review (great beach read material, if you’re interested) are relatively small and short-term double-blind trials comparing an added fiber supplement or food containing that added fiber with a placebo or control group. A number of studies demonstrate that these fibers do, indeed, help improve health outcomes.
But when it comes to population-level health impacts over time, foods packed with naturally occurring fibers generally just have a longer track record, Tewksbury explains. We’ve been looking at correlations between fiber intake and health outcomes for decades across huge populations, and have accrued a meaty body of observational evidence. The foundational link this research has established is between good health and intrinsic fiber, i.e. fruits, veggies, whole grains, beans—not fiber in isolation. The plant foods that naturally contain fiber happen to be exceptionally healthy in general, so it’s hard to suss out what exact benefits can be chocked up to fiber specifically (as opposed to, say, the protein in whole grain products or the antioxidants in fruits and vegetables).
“Where we’re getting that fiber recommendation is not just from fiber itself—it’s based off consumption of fruits and vegetables and whole grains,” Tewksbury explains. That’s why the Dietary Guidelines specifically state that low fiber intake is due to low intakes of fruits, vegetables, and whole grains, and encourage people to eat more of them to increase their fiber intake—not more cookies and bars containing added fiber. Plus, plant foods almost always have a mix of both kinds of fiber, while added fiber products typically contain just one (usually soluble fiber), Dr. Ford notes. That’s not necessarily bad, but it does mean you’re not getting the benefits of both types, especially the digestive health benefits that seem to be most strongly associated with insoluble fiber.
One more uncomfortable truth about added fiber
If you’ve found that eating fiber-enriched cereals or cookies makes you especially gassy and bloated, you’re not alone. That’s one other potential issue with added fibers: the large amount of fiber that some of these products contain. Loading up on any kind of fiber, naturally occurring or added, can cause gas, bloating, and cramping, Dr. Ford says, especially if you’re rapidly upping your intake or not drinking enough water, per the Mayo Clinic. And while technically you could overdo it on the fiber by chomping on oats and apples, the concentration of fiber in foods that contain it naturally is generally lower—whereas some of these added fiber snacks pack in 10, 15, or more grams per serving, making it easy to overwhelming your GI system in just three or four bites. And if you reach for a second (or third) brownie or cookie, that’s just… a lot of fiber. That’s why you might notice you’re particularly gassy or bloated after eating a high-fiber protein bar but not a bowl of oatmeal. (If you do notice a high-fiber food bothers your stomach, maybe try something with a little less fiber, introducing it more slowly to your diet, and drinking more water with it, Dr. Ford says.)
The good news is that stomach distress is probably the worst thing that will happen to you (unless you have a GI condition and have been told to avoid excessive fiber, of course). It’s pretty impossible to “overdose” on fiber, Dr. Ford says, since it doesn’t get absorbed into your bloodstream. In fact, there is no “Tolerable Upper Limit” for fiber, according to the Academy of Nutrition and Dietetics (AND), meaning research hasn’t revealed a level of fiber that is shown to have significant negative health effects on either mineral levels or GI functioning.
The bottom line on added fiber
It’s pretty freaking cool that we can get a fiber boost from something that tastes like dessert, but you probably shouldn’t be relying on fiber-enriched processed foods for the majority of your daily intake. If you’re looking to incorporate a little extra fiber in your diet—to help with constipation or simply up your overall intake—and you feel better reaching for the fiber-fortified version, go for it. There’s nothing wrong with using those foods to supplement your fiber intake (or just because you like them). “They’re great options to enjoy as a treat or dessert that has some additional nutritional value,” Tewksbury says.
Just keep in mind that as tasty and welcome as these foods are in your diet, if you’re trying to eat more fiber to improve the overall nutritional quality of your diet, it’s best to primarily rely on whole foods to help you get there, Dr. Ford says. In other words, don’t assume a food high in fiber is always the more healthful choice—and probably don’t start swapping out all your fruits, veggies, whole grains, and beans for added-fiber brownies.