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Fiber is both diet fad and fixture for good health – a doctor explains why there is no one-size-fits-all way to increase your intake
Fiber is both diet fad and fixture for good health – a doctor explains why there is no one size fits all way to increase your intake. Originally published by The Conversation.
By Jean Liew, Assistant Professor of Medicine, Boston University · 2026-09-23T13:06:07.517Z
Many whole foods, such as fruits, vegetables, legumes and nuts, are high in fiber. bit245/iStock via Getty Images Plus The numbers are clear: Americans aren’t getting enough fiber https://nutrition.org/most americans are not getting enough fiber in our diets/ . Research has consistently shown that high fiber diets are linked to significant health benefits https://theconversation.com/fiber is your bodys natural guide to weight management rather than cutting carbs out of your diet eat them in their original fiber packaging instead 205159 , including a lower risk of cardiovascular disease and colorectal cancer https://doi.org/10.1136/bmj 2020 054370 , as well as improved arthritis symptoms https://doi.org/10.1186/s13075 023 03126 3 . Despite these benefits, there remains a significant fiber gap https://doi.org/10.3945/jn.112.160176 in the typical American diet. The recommended daily fiber intake is 25 grams a day for women and 38 grams a day for men. From 2013 to 2018, only 4% of U.S. adults met their recommended adequate intake http://doi.org/10.1017/S0007114523000089 for dietary fiber. The average fiber intake was about 16 grams a day. Adding fiber to your diet through eating more fiber rich foods or by taking fiber supplements has become a viral health trend https://www.npr.org/2026/05/18/nx s1 5821598/fibermaxxing healthy fiber foods diet benefits . At the same time, the 2025 update to the American dietary guidelines appears to downplay fiber’s role https://cdn.realfood.gov/DGA.pdf in a healthy diet, placing high fiber whole grains at the bottom as the smallest part of the inverted food pyramid. This can be confusing, because the written guidelines themselves continue to highlight the importance of eating whole grains. What does the science say about the health benefits of a high fiber diet? And what steps can you take to incorporate more fiber into your diet? These and similar questions my patients have asked me as a physician scientist https://scholar.google.com/citations?user=8xTeCo0AAAAJ&hl=en prompted me to look further into the latest research on dietary fiber. Basics of dietary fiber Dietary fiber can be found in many sources, and the choices can be overwhelming. Dietary fiber https://doi.org/10.1093/advances/nmab116 refers to carbohydrates your body can’t digest. Many whole foods are high in fiber https://www.mayoclinic.org/healthy lifestyle/nutrition and healthy eating/in depth/high fiber foods/art 20050948 . High fiber foods include raspberries, avocados, oats and other whole grains, and lentils and other legumes. Fiber also comes in supplements such as psyllium husk powder https://doi.org/10.1039/d2fo00560c , known as the brand Metamucil, which comes from a plant called Plantago ovata . Isolated fibers such as inulin https://doi.org/10.1039/d2fo01096h are now increasingly added to foods, including those marketed as high fiber snack bars, keto friendly carbs and even soda. Moreover, not all types of fiber https://doi.org/10.1136/bmj 2020 054370 are created equal.
There are many types of fiber, each with different health benefits. McKeown et al./BMJ, CC BY NC For example, psyllium is a viscous fiber https://doi.org/10.1016/j.jand.2016.09.021 , meaning it forms a gel when added to water. This gel can contribute to early satiety, meaning you feel fuller after eating. Viscous fiber can help lower cholesterol, improve blood sugar levels and blood pressure, lead to a small amount of weight loss, and make bowel movements more regular. Other popular types of fiber are fermented https://theconversation.com/gut microbes are the community within you that you cant live without how eating well can cultivate your microbial and social self 210668 , meaning they are eaten and processed by bacteria that live in your gut. These gut bacteria make proteins that can lower inflammation in the body. Inulin is one type of fermented fiber and can be extracted https://doi.org/10.1016/j.indcrop.2021.113726 from chicory root and Jerusalem artichokes. Nutrition experts recommend getting a variety of fiber rich foods in your diet because of the added benefit of other nutrients in these foods, such as antioxidants https://doi.org/10.1093/ajcn/78.3.579S . Probiotics versus fiber Besides fiber, adding probiotics https://theconversation.com/bacteria in your gut can improve your mood new research in mice tries to zero in on the crucial strains 220935 to your diet may also benefit your gut health. Probiotics are a category of fermented foods that still contain live microbes when you eat them. These include fermented foods https://doi.org/10.1038/s41575 020 00390 5 such as sauerkraut, yogurt and kimchi, which are changed by the addition of live microbes, such as bacteria or yeast. Although the terms sound similar, these fermented foods that have “good” bacteria added to them are not the same as the fiber that gets fermented by bacteria already in your gut. Think of it this way: Fiber provides the material for the gut bacteria to work with. Probiotics provide more “good” gut bacteria to join the community that already exists.
Kimchi is a fermented food that can help spice up a dish and your gut microbiome. alvarez/E+ via Getty Images In a 2021 study, researchers examined the gut microbiomes https://doi.org/10.1016/j.cell.2021.06.019 of 36 healthy adults who either ate a diet high in fiber or a diet high in fermented foods. They found that those who ate a high fiber diet had a gut microbiome https://theconversation.com/hangry bacteria in your gut microbiome are linked to chronic disease feeding them what they need could lead to happier cells and a healthier body 199486 that was more active in making the enzymes that break down fiber. That means these microbes got better at using the fiber they were fed to make byproducts helpful for the body. In contrast, those who ate a diet high in fermented foods had a gut microbiome that was more diverse, meaning they had many different species of bacteria in their guts. They also had lower levels of inflammation. Many chronic conditions can raise levels of inflammation in the body, and exposure to inflammation can put stress on the body, contributing to issues such as cardiovascular disease https://doi.org/10.1016/j.jacc.2025.08.047 . The results of this small study point to the possibility that combining high fiber and fermented foods in your diet could synergize their health benefits in nourishing the gut microbiome. How can you get more fiber in your diet? With so many options available, what’s the best way to increase your fiber intake? Some barriers https://doi.org/10.1177/02601060251348552 to eating enough dietary fiber include cost, accessibility and tolerability https://doi.org/10.1093/advances/nmac091 . Some high fiber whole foods, such as berries, can be expensive. Highly fermentable fibers, such as inulin, often cause bloating and discomfort https://doi.org/10.1016/j.jada.2010.03.025 , especially if you aren’t used to eating them. This can be a turnoff for high fiber drinks and snacks, since they contain so much fiber in a single serving. There are many ways to increase the amount of fiber you eat on a daily basis. The general recommendation https://www.uclahealth.org/news/article/beat bloat 4 tips increasing your fiber intake is to do it slowly to allow your body to get used to the higher amount of fiber and to stay hydrated so your body can use the water along with the fiber for optimal bowel health. Most importantly, try a variety of fiber sources to figure out what’s right for you. Some people will be able to reach the recommended fiber levels by eating whole foods alone; others will add supplements or eat foods with added fiber. There is no one size fits all healthy diet.
There are many ways to increase fiber in your diet. Choose what works best for you. Denis Borisov/iStock via Getty Images Plus Unlocking the full benefits of fiber More focused research https://doi.org/10.1093/advances/nmaa109 is needed to understand more about the types of fiber that are beneficial to health, in what doses, and in what combinations. But these nutrition studies can be tricky. My research focuses on finding links between fiber and different diseases in observational data and figuring out how to test them in a clinical trial. For example, one large observational study found an association between higher self reported intake of whole grains and lower risk of arthritis https://doi.org/10.1136/annrheumdis 2016 210810 . But researchers still need to test this connection in clinical trials, which requires deciding the right type and amount of whole grains to recommend, as well as the right length of time to test this diet. While there have been many small clinical trials on fiber, they have not been big enough, specific enough or broad enough to provide answers that can be put into guidelines for everyone. Adequate funding has been one major hurdle to starting such large, well designed trials. At the same time, scientists already know many confirmed benefits of dietary fiber, and the gap lies in educating the public https://doi.org/10.1136/bmj 2020 054370 and making changes so that foods high in fiber are affordable and accessible to more people.
Jean Liew receives funding from NIH NIAMS.