165 | Fiber and Gut Health: Why “Eat More Fiber” Isn’t Enough

We tell patients to eat more fiber all the time. Constipation? Eat more fiber. High cholesterol? Eat more fiber. But here's the problem. Most patients don't actually know what that means. And honestly, we don't always explain it very well either. Fiber is not one single nutrient that behaves the same way in every food or every person. Different fibers have different properties. They can support different health goals. And some fibers also serve as fuel for the microbes living in the gut. Welcome back to the Exam Room Nutrition Podcast. I'm your host, Colleen Sloan. I'm a PA and dietitian, and today we are moving beyond the vague recommendation to eat more fiber. With support from our sponsor, Neurofiber, we're going to be talking about why fiber type and fiber diversity matter, how fiber interacts with the gut microbiome, and what we can actually say to patients instead of just telling them to eat more fiber. Neurofiber is a fiber bar made with 14 prebiotic and whole food fiber sources developed to support digestive health, microbiome diversity, and the gut brain access. Check out their resources and grab your trial pack at neurofiberhealth.com or request free samples for healthcare practitioners using the link in the show notes. Now, before we talk about fiber, we need some background on the gut microbiome to understand exactly what fiber is doing there. So the gut microbiome is a community of microorganisms that live primarily in the large intestine, but also throughout your entire body, including small intestines, skin, and even lungs. That includes bacteria, along with viruses, fungi, and other microbes. I like to explain it to patients that the microbiome is like a rainforest. A healthy rainforest is not made up of one type of tree. It contains many different plants, animals, insects, and organisms all interacting with each other. That diversity helps the ecosystem remain resilient. And the gut works in a similar way. It contains many different microbes performing different jobs. And what we eat helps determine what those microbes have available to work with. Certain fibers escape human digestion and reach the colon, where they become fuel for different gut microbes. But not every type of fiber behaves the same way or feeds the microbiome in the same way. That's why simply telling patients to eat more fiber is actually too vague. Think back to school or your training, you were probably taught to divide fiber into two categories, soluble and insoluble. That's a very helpful starting point, but it's incomplete. A more useful way to understand fiber is to look at three properties: solubility, viscosity, and fermentability. In other words, does it dissolve in water? Does it form a gel? And can it be fermented by gut microbes? Those characteristics help determine what a fiber actually does in the body. For example, some fibers form a thick gel in the digestive tract. This can slow digestion and nutrient absorption, which is one reason certain viscous fibers help support glucose control and lower cholesterol. Cilium is a really good example of this. It forms a gel, holds onto water throughout the colon, and resists fermentation. So this allows it to soften hard stools and constipation while also adding form to loose stools. Cilium can be effective for those purposes, but it doesn't necessarily feed the diverse microbes in the gut. Other soluble fibers such as inulin, fructooligosaccharides, galacto oligosaccharides, and resistant starch do not form the same type of gel. Instead, gut microbes readily ferment them, producing short chain fatty acids. These fermentable fibers are often what we mean when we talk about prebiotics. The three most commonly discussed short chain fatty acids are acetate, propionate, and butyrate. These compounds are one of the ways the microbiome influences the environment inside the gut. Butyrate, for example, is an important energy source for the cells lining the colon. Short chain fatty acids also help support the intestinal barrier and act as signaling molecules involved in immune function and metabolism. Researchers are continuing to study how they may contribute to communication between the gut and the rest of the body. Not every fiber is fermented, though, and that brings us to coarser insoluble fibers such as wheat bran and cellulose. These fibers do not dissolve in water. Instead, they help stimulate movement through the gut and can increase stool bulk, which supports regularity. The point here in this short summary of fibers is that different fibers perform different jobs. So when we tell someone to eat more fiber, the next question in your mind should be: what are we trying to help? Constipation, cholesterol levels, blood glucose, dietary quality, or are we providing more fermentable substrates for the gut microbiome? The goal should help guide your recommendation. So that brings us to the question, does quantity matter? Absolutely. General recommendations are based on about 14 grams per 1,000 calories, which works out to roughly 25 to 38 grams per day for most adults. However, 95% of Americans don't meet these recommendations, and the average American only consumes 17 grams per day. But grams alone do not tell us everything. Two foods can provide the same amount of fiber while containing very different fiber structures and plant compounds. Different microbes also prefer different substrates. That means eating a variety of whole grains, legumes, fruits, vegetables, nuts, and seeds gives the gut microbiome a broader range of fermentable material than relying on the same food or the same isolated fiber over and over again. So we do want patients to get enough fiber, but we also want them to get it from a variety of sources. A single fiber supplement can still be very useful. Cilium, for example, has specific evidence-based uses. But a targeted fiber supplement and a diverse dietary pattern are not interchangeable. They may serve different purposes. And for patients who cannot consistently meet their needs through food alone, a thoughtfully formulated fiber product may help fill part of that gap. This is what caught my attention when I learned about neurofiber and tried their bars. Neurofiber bars were developed around the idea that fiber diversity may offer something different from relying on one isolated fiber alone. The neurofiber bar contains 14 prebiotic and whole food sources of fiber, including a five-fiber prebiotic blend. They're also gluten-free and made without artificial sweeteners, emulsifiers, or inulin, and contain 11 grams of fiber per bar. Now I really loved the clean ingredients as well. It honestly feels like you're reading a recipe you could make at home. So let me just read off some of the ingredients in their lemon cranberry bar: date paste, almonds, cashews, walnuts, coconut nectar, dried cranberries, gluten-free whole grain oats, pumpkin seeds, lemon juice, chia seeds, and flax seeds. All real whole food ingredients. Neurofiber has also done some really interesting research in Parkinson's. They did an ex vivo study, which means the study was done outside the body using a simulated intestinal fermentation model. So this was not a human outcome study, but it was a really cool way to look at how fibers behave when they're exposed to gut microbes. They compared single fibers, common constipation-related controls, and more complex fiber blends. And what they found was the more complex blend, the one used to help develop neurofiber, produced more short chain fatty acids than the single fibers and controls in that model. Remember, short chain fatty acids are those helpful compounds produced when gut microbes ferment certain fibers. It also produced relatively low gas in the model, which is really interesting because that's one of the biggest complaints that patients have when they increase fiber too quickly. Neurofiber has also done early pilot research in people with Parkinson's disease, looking at things like gut inflammation and constipation. The research behind that explains the name. The neuropiece comes from the company's interest in the gut brain connection. But the reason I'm bringing this to you today is broader than Parkinson's. It's the idea that fiber type and fiber diversity matter. So when you're encouraging patients to eat more fiber, here are three ways to make that advice more practical. First, I would suggest adding one fiber source to something they already eat. Add some berries to their yogurt, add beans to a taco bowl, sprinkle chia or ground flax to oatmeal, add a vegetable to their frozen dinner. Using the foods and routines your patient already has makes increasing fiber much easier. Second is increase gradually. This is so important. You may remember the fiber maxing trend where people on the internet were shoving their faces with high quantities of fiber all at once, and then they wondered why their tummies hurt. So, as with most dietary changes, it's best to start low and go slow. Third, I love using a food-first approach without pretending that convenience doesn't matter. Whole foods provide fiber along with other things like vitamins, minerals, and other plant compounds. This should remain the foundation. But there is a place for supplements. Some patients struggle with appetite, food access, sensory preferences, preparation time, or consistency. And for those patients, a well-formulated fiber product like neurofiber can be one tool to help bridge the gap. So the next time you're tempted to tell a patient to just eat more fiber, pause, think of this episode, and get more specific. What's their goal? Are you trying to fill the fiber gap that most Americans have, improve their stool consistency, support cholesterol levels, or provide more fermentable fiber for gut health? Once you know the goal, you can think about the amount, the type of fiber, the patient's tolerance, and what actually fits their life. It's not just about more fiber, the right fiber from a variety of sources in a way patients can actually follow through with. So thanks again to Neurofiber for sponsoring this episode. Check out neurofiberhealth.com. And if you're a healthcare practitioner, don't forget to grab your free samples using the link in the show notes to try the fiber bar that has 14 prebiotic and whole food fiber sources. So thanks for carving out some time for nutrition today, and I will see you next week.