The Fiber Myth: Why We’ve Been Misled About What Our Bodies Really Need
For as long as most of us can remember, fiber has been sold as the cure-all for digestive health. Doctors, dietitians, and cereal commercials tell us to load up on bran, oats, and “whole grains” for the sake of our guts and hearts. But what if fiber wasn’t necessary at all? What if the fiber story was never really about health, but about selling more carbohydrate foods?
Dr. Zoë Harcombe, a Cambridge-educated nutrition researcher, has spent years digging into the science behind dietary guidelines. Her conclusion is clear: fiber is not an essential nutrient, and much of what we’ve been told is based on flawed studies, marketing spin, and a lot of wishful thinking.
The Problem with the “Essential Fiber” Claim
First, let’s talk about what “essential” means. Essential nutrients are those our bodies cannot make on their own and must be supplied through food, like certain amino acids and fatty acids. There are essential proteins. There are essential fats. But there are no essential carbohydrates and since fiber is a subset of carbohydrate, there is no essential requirement for fiber either.
As Dr. Harcombe put it:
“There are essential fats, there are essential proteins, there are no essential carbohydrates. Fibre is a subset of carbohydrate. De facto, there is no requirement for fibre whatsoever.”
This simple truth dismantles the entire narrative that fiber is something we can’t live without.
Fiber and Nutrient Loss
Not only is fiber unnecessary, it can actually work against us. Because fiber is indigestible, it can interfere with nutrient absorption. Food moves through the gut more quickly, meaning vitamins and minerals don’t get absorbed as effectively. Harcombe explains that at the point fiber leaves the body, most of the usable nutrition has already been stripped out. If anything, fiber can reduce the amount of nutrition we retain from food.
Contrast this with animal foods: nutrient dense, highly bioavailable, and almost completely absorbed. When I transitioned from a keto lifestyle to an animal-based diet after nearly a decade, constipation was never an issue. That’s because there is so little waste. The body uses nearly everything. In fact, there’s a case to be made that the absence of waste is a sign of efficiency not a problem.
Meanwhile, a vegetarian or plant-heavy diet requires supplementation, not because animal products are missing, but because fiber literally blocks the body from fully absorbing what’s there.
Constipation: A Fiber Problem, Not a Fiber Solution
We’ve all heard it: if you’re constipated, you need more fiber. Doctors say it, diet books repeat it, and grocery aisles are full of fiber supplements promising relief. But the reality is very different.
A 2012 clinical trial led by Ho et al. looked at people with severe constipation. The researchers reduced participants’ fiber intake and in many cases removed it entirely. The results were striking. Every single symptom of constipation disappeared in every single patient.
Harcombe summarized it bluntly:
“They… stopped your fibre intake. … Every single symptom in every single person disappeared.”
This flips the common wisdom on its head. Constipation is not a lack of fiber. For many people, it is the direct result of fiber.
How Fiber Got Its Health Halo
So how did fiber become the star nutrient? Part of the story traces back to moral movements of the 1700s, where reformers like Sylvester Graham preached against meat and promoted whole grains as virtuous. Fast-forward to the 20th century, and cereal companies picked up the message. Selling “healthy” grains became a business model, even though products like bran flakes often contain 20 percent sugar to mask the taste.
As Harcombe notes:
“You need to consume those whole grains… That’s how they want us getting fibre… Bran flakes… often 20 percent sugar to disguise the taste of the bran.”
Fiber became the excuse to sell more carbohydrate foods, and with it came pharmaceutical tie-ins. People told to eat fiber-rich carbs often got worse, and when symptoms persisted, the next step was prescription medication. The cycle fueled industries, not health.
The Body Knows What to Do
The truth is that our bodies are brilliantly designed. We can empty the colon without a fiber broom sweeping through it. Animal foods provide highly absorbable nutrition, leaving little behind. There is no evolutionary evidence that we require plant fiber for gut function.
And when it comes to blood sugar and heart health, the picture is no clearer. Studies that claim fiber is protective often compare “high-fiber” diets (whole grains and starchy vegetables) with “low-fiber” diets that are still full of junk food and sugar. What’s missing are direct comparisons with low-carb, low-fiber diets centered on meat, eggs, and dairy diets that consistently deliver stability, satiety, and nutrient density.
Time to Question the Narrative
Fiber has been marketed as a health savior for decades, but the science doesn’t hold up under scrutiny. It is not essential, it may block nutrient absorption, and it often worsens the very conditions it’s prescribed to fix.
This is, of course, a very short and basic explanation, but for now it serves as food for thought. Like anything in the nutrition sphere, there is much that needs to be questioned, revisited, and often turned on its head after decades of unquestioned narratives. I want this blog to make you pause and challenge everything you think you know, because everything we have been told for so long deserves to be examined closely. We have to rely on science, real studies, and verifiable evidence not slogans, marketing campaigns, or outdated dogma.
As Dr. Harcombe puts it:
“Fibre is a subset of carbohydrate. De facto, there is no requirement for fibre whatsoever… If we don’t need it, is it good for us? And the short answer is no.”
If you’ve ever felt worse after upping your fiber, you’re not imagining it. If you’ve thrived on a diet rich in animal foods, you already know what the research is finally admitting: our bodies don’t need fiber. What they need is real, nutrient-dense food.
I’ll continue to explore these myths and share the evidence that challenges mainstream nutrition. If this made you think differently about fiber, subscribe to the blog or follow along on Mind-Body Synergy.
References
Harcombe, Z. (2019). Why do studies conclude that fiber is associated with better health? Retrieved from zoeharcombe.com
Harcombe, Z. (2022). Fibre, CVD & Inflammation. Retrieved from zoeharcombe.com
Harcombe, Z. (2022). Fibre – ask why, not how. Retrieved from zoeharcombe.com
Harcombe, Z. (2025). 12 Questions about Fibre. Retrieved from zoeharcombe.com
Ho, K. S., et al. (2012). Stoppage of dietary fiber intake reduces constipation and its associated symptoms. World Journal of Gastroenterology, 18(33), 4593–4596. PubMed PMID: 22969258
Defeat Diabetes (2023). The Fibre Myth with Zoë Harcombe. Retrieved from defeatdiabetes.com.au
This content is never meant to serve as medical advice.
In crafting this blog post, I aimed to encapsulate the essence of research findings while presenting the information in a reader-friendly format that promotes critical thinking and informed decision-making.
