851. A current nutrition trend encourages people to dramatically increase their fiber intake. But how much fiber is actually helpful And when can “more” start to backfire?
851. A current nutrition trend encourages people to dramatically increase their fiber intake. But how much fiber is actually helpful? And when can “more” start to backfire?
Find a transcript here.
Recommended Resources:
The Bloated Belly Whisperer by Tamara Duker Freuman
Regular, by Tamara Duker Freuman
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Fiber-maxxing is all over social media. And it’s true that most Americans are falling well short of the recommended intakes. But it’s always possible to take a good thing too far. So, what are the risks of getting too much fiber?
Hello there I’m Monica Reinagel and you are listening to the Nutrition Diva podcast, a show where we take a closer look at nutrition news, research, and trends so that you can make more informed decisions about what you eat.
Today, we’re talking about fiber-maxxing—a trend that’s been all over social media, encouraging people to push their fiber intake higher and higher in the name of gut health, blood sugar control, weight management, and disease prevention.
On the one hand, this focus on fiber may have some benefits. Most Americans get nowhere near the recommended amount of fiber, and higher-fiber diets are consistently associated with better digestive health, improved cholesterol levels, and a lower risk of several chronic diseases.
But is it possible to get too much fiber?
People promoting fiber-maxxing often report daily intakes of forty, fifty, or even sixty grams of fiber or more. That’s significantly higher than the typical American intake, which hovers somewhere around 15-18 grams per day. It’s also well above the recommended daily intake, which typically ranges from 25 to 35 grams per day, depending on your age and your sex.
Now i practice, that might involve adding large amounts of bran, chia seeds, flax, beans, lentils, vegetables, berries, and sometimes fiber supplements or powders to your meal plans. And the claim is that this will optimize your gut microbiome, blunt blood sugar spikes, reduce your appetite, and even lower your risk of colon cancer and other diseases.
These are all science-backed benefits of higher-fiber diets. And with colon cancer rates mysteriously on the rise in younger adults, it also makes sense to me that Gen Z is paying attention to lifestyle tweaks that focus on gut health.
And it is also true, as I said that the typical American adult would benefit from getting more fiber. On average, we’re only getting about half the recommended amount. But is there a point where the benefits level off—or even start to reverse?
Well, first, let’s take a closer look at how those recommended intakes were established in the first place. Historically, recommended dietary allowances (RDAs) are based on the amount needed to prevent acute diseases associated with specific nutrient deficiencies. So the RDA for vitamin C is enough to prevent scurvy, and the RDA for B1 is enough to prevent beriberi. Many nutrients, such as vitamin A or selenium, also have what we call Tolerable Upper Intake Levels, or ULs. And intakes above this level may increase the risk of symptoms associated with toxicity.
Now over the years, RDAs have also been adjusted, as we learn more about the long-term impacts of various nutrients. So, while the early RDAs for vitamin D may have been about preventing rickets, they were later adjusted upwards in an effort to also support long-term bone health and osteoporosis prevention.
Now there’s no acute disease associated with fiber deficiency. (Constipation is not really considered a “disease.”) So fiber doesn’t have an RDA. Instead we have a recommendation for Adequate Intake (AI), and this is on a sliding scale based on total calorie intake. Specifically, the recommendation is 14 grams of fiber for every 1000 calories you eat. And this is based mostly on observational evidence linking higher fiber intake with better digestive health, lower cholesterol levels, and reduced risk of heart disease and colon cancer.
It’s also worth noting that these recommendations were set a couple of decades ago, before we understood as much about the gut microbiome. We now know that many of fiber’s health benefits are not simply about providing “roughage,” but about providing fuel for gut bacteria. These beneficial bacteria ferment certain fibers into short-chain fatty acids that help regulate inflammation, immunity, metabolism, appetite, even mood.
Research confirms that increasing fiber intake can produce measurable changes in the gut microbiome in a relatively short period of time. Now the long-term impacts of that on health and disease are harder to measure in controlled trials. But many researchers and clinicians argue that fiber recommendations really should be set a bit higher, at least for people who are able to tolerate higher fiber intakes. Because as anyone with IBD or IBS will tell you, not everyone can.
At this point, there is also no tolerable Upper Limit (UL) for fiber. Because according to the Institutes of Medicine (IOM), fiber from foods is unlikely to be overconsumed. (To which Gen Z said, hold my high-fiber beer.) But the IOM also noted that if functional fibers and supplements become more ubiquitous, an UL might need to be considered in the future. And perhaps that future has arrived.
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So, what could go wrong if you ramp up fiber too far or too fast?
Well, the most common issues are gastrointestinal. Even for people without IBS or other conditions that make fiber problematic, increasing your fiber intake too quickly can lead to bloating, gas, cramping, constipation, or diarrhea. Those symptoms aren’t a sign that fiber is “bad" for you, but they are a signal that the gut might need a little time to adapt to a higher fiber diet.
And constipation is a particularly common paradox. So fiber is often recommended to relieve constipation. But in some cases, especially when fiber is ramped up too quickly or without adding enough fluids, it can actually make constipation worse. Interestingly, studies of people with chronic constipation have found that many of them were already consuming high amounts of fiber, and that reducing fiber sometimes improved symptoms.
Just as a quick aside, when it comes to constipation and other digestive discomforts, registered dietitian Tamara Duker Freuman is my go-to expert. I regularly refer to and recommend her books, The Bloated Belly Whisperer and Regular, as definitive sources for detailed, useful guidance on these topics.
Another potential consideration is where you’re getting all this fiber from. Whole foods like beans, vegetables, fruits, and whole grains come packaged with a certain amount of water plus other nutrients, and they represent a mix of fiber types. So while it’s still a good idea to ramp up gradually to minimize any digestive discomfort, these whole foods at least have some measure of portion control built in.
Many fiber-maxxing routines rely heavily on fiber supplements, powders, or other concentrated sources of fiber. When these are taken in large amounts, especially without enough fluid, they can increase intestinal discomfort or even create intestinal blockages.
Relying too heavily on supplements also overlooks the importance of getting fiber from a variety of sources. Because fiber is not a single nutrient but a whole family of nutrients. There are soluble and insoluble, viscous and non viscous, fermentable and non fermentable, probiotic and non-probiotic fibers. And each of those has different properties and benefits. So if you are relying more on whole foods for your fiber, you are more likely to be getting more variety. And if you’re leaning too hard on supplements, your fiber portfolio can become dangerously imbalanced.
There’s also a question about nutrient absorption. Certain types of fiber can bind to minerals like calcium, iron, zinc, and magnesium in the digestive tract. When that happens, some of those minerals pass through the body instead of being absorbed. But you don’t necessarily need to worry about fiber causing mineral deficiencies.
People eating higher-fiber diets generally maintain or even improve their body stores of minerals like calcium, magnesium, and zinc. And that's mostly because the foods that provide fiber are also rich sources of those same nutrients. Fiber supplements, on the other hand, usually don’t bring minerals along for the ride, so you're not getting that nutritional compensation. But even then, the effect on mineral binding is really unlikely to be a problem for someone who is reasonably well nourished.
But could fiber-maxxing go so far that it actually starts causing problems? Friends, any good thing can be taken too far. While getting 50 or 60 grams of fiber may be great, 80 or 100 grams may well push things over the edge. And regardless of what someone on TikTok maybe claiming, there’s really little additional benefit to getting that much fiber.
If you’re interested in increasing your fiber intake—whether you call it fiber-maxxing or not—here are a few best practices that can help you get the benefits without the unpleasant side effects.
1. First, go slowly. Your gut and your microbes need time to adapt. Doubling your fiber intake overnight is far more likely to cause bloating and discomfort. And gradual increases tend to be much better tolerated.
2. Second, drink plenty of fluids. Because as fiber goes up, fluid needs usually go up as well.
3. Third, prioritize food sources of fiber. Whole foods like beans, lentils, whole grains, vegetables, fruits, nuts, and seeds provide fiber along with vitamins, minerals, and you get a mix of fiber types. Foods that are fortified with fiber can also help close the gap. Fiber pills and powders are OK, but they should be supplements, not your primary source.
4. Fourth, you may not respond to all fiber sources the same way. Some people tolerate oats better than they tolerate wheat bran, or beans better than raw vegetables or vice versa. Certain fermentable fibers are more likely to cause gas and bloating. It’s often a matter of experimenting to find the types of fiber that work best for you.
5. And finally, variety is key. Different types of fiber feed different gut microbes and support different aspects of health. Eating a wide range of plant foods is generally more beneficial—and often more comfortable—than relying heavily on just one or two high-fiber staples or supplements.
One important caveat: people with digestive diseases, active gut inflammation, or a history of gastrointestinal surgery need to be especially cautious with fiber increases. In these situations, working with a registered dietitian or another qualified nutrition professional can help fine-tune fiber choices and troubleshoot problems safely.
I’ve got a whole bunch of links to related episodes on fiber, FODMAPs, and digestive health in the show notes, including my interviews with registered dietitian Tamara Duker Freuman.
If you have a topic or trend you’d like me to take in an upcoming episode, you can email me at nutrition@quickanddirtytips.com.
Nutrition Diva is a Quick and Dirty Tips podcast. Holly Hutchings is our Director of Podcasts. Steve Riekeberg is my audio engineer, Morgan Christianson heads up Podcast Operations & Advertising, Rebekah Sebastian is our Manager of Marketing and Publicity, Nat Hoopes is our Marketing and Operations Assistant and Maram Elnagheeb is our Podcast Associate. Thanks to all of them and thanks to you for listening! I'll see you next week.