The #1 Most Dangerous Fiber in the World

The most dangerous fiber is often disguised as healthy, but could be silently damaging your health. In this video, we’ll cover the connection between fiber and gut health, the worst fiber foods to avoid, and the hidden problems with refined fiber they don’t want you to know about.

The number one most dangerous fiber in the world is refined fiber. What the heck am I talking about refined fiber? We spent many many years studying refined sugars and refined carbohydrates, right? Starts off with sugar cane with all the different vitamins and minerals and then we strip it off and then we have this refined sugar and we find out it’s bad for us. Well, when we talk about fiber, fiber is not for us as humans.

It’s for our microbes and we’re doing the same exact thing we did to our bodies with refined sugar as we’re doing to our microbes with refined fiber. Certain fiber in its whole form can feed the microbes and make them thrive. Other fiber that’s refined is basically junk food for the microbes. The information I’m going to share with you you probably never heard. It’s fascinating.

You need to know about it because right now there is such a fiber craze. Everyone’s like trying to get as much fiber as they can and for a lot of people it’s creating a lot of problems. And some fascinating research on this topic too where they’re feeding mice refined fiber and some of them are developing liver cancer. More on that in a little bit. But the study was published in Cell, one of the most prestigious scientific journals in the world and I’m going to walk you through why that happens.

When you eat a bean or an onion or a berry, you don’t just have fiber sitting in there, okay? That fiber is physically bound to something called polyphenols. So in other words, when you’re eating plant fiber, it’s not just coming as fiber. It’s bound to something else very very tightly. Maybe you’ve heard about polyphenols.

They’re in red wine, they’re in berries, green tea, dark chocolate, but that’s the least interesting thing about them. Here’s what you need to know. Every single plant on Earth has polyphenols and they’re literally woven together with fiber like this, okay? They’re bonded in the cell wall. When you eat them, they’re supposed to travel all the way through your digestive system down into your gut where your body then breaks them apart.

But they’re meant to be consumed as one package, not separate things and it’s very very important to know that one concept because these trillions of microbes have evolved over millions of years to receive information from this one unit itself and not just fiber. So when you eat a plant, this whole unit goes into the body, the microbe receives it as one unit and the polyphenols are trapped in the fiber. They’re the ones that decide which bacteria get to thrive and which ones get shut down. And this is definitely what the fiber supplement industry does not want you to know. I don’t even know if they know it themselves, but the polyphenols are like the air traffic controllers.

They’re like a guidance system for what happens to this fiber. So think of your colon like this airport, right? You have all these flights going on and that’s all the bacteria. And certain bacteria want access to the runway and of course all of them want fuel. When you eat the whole fiber with all these polyphenols attached, then you get direction on what microbes actually get the fuel and how much fuel they get and make sure also they don’t get too much fuel.

Fascinating research published in the Journal of Nutritional Biochemistry showed that when gut microbes break down polyphenols, the beneficial species multiplied while the ratios of bad bacteria dropped significantly. So the polyphenols weren’t necessarily just feeding the bacteria randomly. They were selectively promoting the good bacteria and suppressing the bad bacteria. And the microbes that got promoted and got fed, they made short chain fatty acids. This is the fuel for your colon cells.

And in a 2025 review in Frontiers in Nutrition, they confirmed this across multiple human trials. When people ate foods rich in both fiber and polyphenols things like nuts or spices or whole grains, they consistently grew more microbes that make these short chain fatty acids. The anti-inflammatory effects were much much stronger than the group that just got the fiber and also the group that just got the polyphenols alone. These two things work together. They both amplify each other.

So the fiber is the fuel for the microbes, the polyphenols are the direction, the guidance system of what happens to that fuel and who gets the fuel and how much they get. When you remove the polyphenols and you get refined fiber, I’ll give you some examples like chicory root fiber extract, okay? Or soluble corn fiber or tapioca fiber. These are refined fiber. This is like ultra-processed food for your microbes because they don’t have the polyphenols.

And the way they make this is the same way they make industrial starch and sugar. They’re adding chemical processing, they’re adding certain enzymes to break things down. They’re adding heat and they’re basically refining it. They have to use heat and chemicals and enzymes to break this bond. So then you’re left with this pure fiber fuel without the guidance system, without the air traffic controller.

A researcher at Penn State named Vishal Singh put it very simply. He said when we eat fiber from whole food, we’re consuming a mixture of many different types of fiber alongside the compounds. Now here’s the thing, if you actually start reading the ingredients and totaling up how much fiber is like in a fiber bar, they put in 15 g of fiber. If you took 15 g of fiber from real food, equivalent to having 2 lb of food as fiber. That’s a lot of fiber hitting the gut all at once and we’re talking about isolated fiber without the guidance system.

So what you’re seeing in the food system right now because the food industry has to keep the right texture, the mouthfeel, they’re trying to find substitutes for fat and so now they’re going to all sorts of synthetic fibers. And what you have to realize is all of this fiber is refined. It’s processed fiber and it’s being put in food in very large amounts. So what happens is you’re going to get a lot more fermentation which is going to overwhelm the microbes. So a lot of people ask me, what supplements do I recommend?

Now of course I’m not biased of my own high quality supplement line, but if you go to Amazon and type Dr. Berg supplements, you’ll find more information. So when you consume refined fiber, there’s three things that happen. Number one, the wrong bacteria take over because remember you don’t have the guidance system of who gets what. Number two, the fiber is going to ferment way too fast in the wrong place.

Now this is critical. With whole food, it’s a slow process of breaking things down. But in refined fiber, it’s already broken down. By the time it hits the small intestine where you really don’t want a lot of fermentation if any, that’s where you’re going to start getting fermentation and this is a really big problem. They call it small intestinal bacterial overgrowth and I don’t know if you know this, but we don’t want a lot of bacteria in the small intestine.

We want it mainly in the large. Then number three, the lower colon starves. It doesn’t get the fiber. It doesn’t get the fuel it needs. So what is it going to do at this point?

It has no choice. It’s going to have to eat its own mucus layer. Now we get leaky gut. Now we start developing autoimmune issues. Now we get inflammation in our gut and pain and all sorts of GI issues.

So in 2018, researchers at the University of Toledo published a study in the journal Cell, one of the most respected scientific journals in the world. They fed mice a diet containing inulin which is a fiber. Guess what? The mice developed liver cancer. When tho