For decades, fiber has been touted as an essential component of a healthy diet. The supposed benefits of a high-fiber diet have been drilled you’re your consciousness through recommendations by doctors, government, and the food industry alike, yet many of these health claims have not been proven by research.

In fact, many studies have demonstrated that excess intake of fiber may actually be harmful, particularly for gut health.

You have probably been told that fiber is also absolutely necessary for proper digestive function. While fiber does perform numerous valuable functions for the gut (like producing beneficial short-chain fatty acids and aiding gut health) it might not be absolutely necessary in terms of regulating bowel movements.  

Increased fiber intake has been associated with lower rates of coronary heart disease, stroke, hypertension, diabetes, obesity, and certain GI disorders. This suggests that it provides some human health benefits.

However, in terms of digestion regulation, the literature might not be all in favor of the absolute necessity of dietary fiber. In many studies, when individuals suffering from certain GI conditions are put on a low-fiber diet, symptoms of constipation, bloating, flatulence, and diarrhea actually improve.

Furthermore, when those struggling with GI issues were given fiber supplements to increase their fiber intake, symptoms of gas, constipation, bloating, and diarrhea got worse! This stands in stark contrast to what many people recommend or think is true.

Many following a carnivore diet report that they have no problem “going” on the diet—especially once the digestive system gets used to the change in dietary composition.

In reality, the idea that meat somehow “causes” constipation makes little intuitive sense, especially in an evolutionary context.

Fibre, therefore, may not be essential for a healthy human diet. This may sound like a bold claim but bear in mind that all of the evidence supporting fibre in the diet is in the context of high carbohydrate consumption.

It is important to assess what happens when you look at the science in the context of better human health. Is fibre still as beneficial, does it stack up to the claims or is it just a band aid for a bigger problem?

What Is Fibre?

Fibre is a carbohydrate in plant foods that humans can’t digest. There are two types of fibre:

·       Soluble - Fibre that can be fermented by gut bacteria in the colon to create short chain fatty acids (energy)

·       Insoluble - Fibre that can’t be broken down by the stomach acids or bacteria in your gut.

The claimed benefits of fibre include:

·       Improved bowel movements.

·       Helps maintain gut health.

·       Lowers cholesterol levels.

·       Controls blood sugar levels.

·       Aids in achieving healthy weight.

·       Helps you live longer.

In fact, it’s thought to be so beneficial that fibre is now listed as an essential component of a healthy diet. So much so that fibre is probably the number one concern I hear from clients when discussing the option of a more meat-based diet.

There are 4 major concerns when it comes to removing fiber:

Fibre And Constipation

Due to the fact that so many people believe that fibre is essential and aids with constipation that one would assume the benefits are backed up by science.

Unfortunately, there appear to be no significant randomised control trials on the benefits of fibre on gut health.

probably the most comprehensive study on fibre and symptoms of constipation included 63 participants who presented with constipation and were put on high, medium, low and zero fibre diets.

At the beginning of the study, all participants had constipation and strain, with some experiencing bloating, bleeding and pain. A high fibre diet was found to increase or exacerbate the number of symptoms, a reduced fibre diet experienced a modest reduction in symptoms.

Those patients following a zero-fiber diet experienced nothing! This is not due to missing or undocumented data. Not one patient on the zero-fibre diet had any negative symptoms. Not only did they eliminate their symptoms but they had just one bowel movement per day compared to one bowel movements every 6.83 days on in the high fibre group.

Take away: Fibre may not be so good for constipation. When you think about it, this really is not that surprising. How does adding more bulk to a stool make it easier to pass?

Fibre And Gut Health

Another benefit claimed by the agricultural industry is that soluble fibre is what precedes the production of short chain fatty acids when it is digested by bacteria in the colon. These short chain fatty acids nourish the cells that line the colon, called colonocites, and, as a consequence improve gut health.

While it is true that colonocites use short chain fatty acids for nourishment, this only happens AFTER they have been converted into beta hydroxybutyrate, or in other words, ketones.

Not only is fibre not the only source of short chain fatty acids or ketones but studies have shown that switching to an animal based diet changes the gut microbiome and produces more short chain fatty acids than a plant based diet.

Take Away: The benefits of fibre and gut health fail to hold up to scientific scrutiny and it is possible to obtain more short chain fatty acids from an animal-based diet.

Fibre And Blood Sugar

This is one of the more misleading claims about fibre because while on the surface it is absolutely correct. Studies have shown that fibre does appear to control blood sugar levels. This is, however, only true in the context of a high carbohydrate diet.

Furthermore, in order to consume a high fibre diet, you need to eat a lot of carbohydrates - the very thing that directly contributes to high blood sugar levels.

In other words, the logic here is that if you have a high carbohydrate diet that increases your blood sugar, you should add fibre to it reduce blood sugar.

Why not just have a low carbohydrate, low fibre diet and avoid high blood sugar and the ill effects of a high fibre diet in the first place?

Fibre And Weight Loss

Weight loss is possibly one of the most talked about subjects in our modern times and as such, there are multiple studies on the intake of fibre and its association with weight loss. Unfortunately, almost all of the studies are on people on the Standard American Diet (SAD) which is, by default, extremely high in carbohydrate. When looking at fibre in the context of a neutral gut microbiome, a much clearer picture emerges. Whilst this is not possible in humans due to ethical concerns, it has been done in mice.

One such study took gut bacteria from overweight mice and implanted it in mice that were bred to have no gut microbiome. The mice that received bacteria from the overweight mice became obese themselves:

This begs the question of how did the germ-free mice get fatter? They began to produce more energy in the form of short chain fatty acids.

You might be wondering how this relates to fiber. relate to fibre. The germ free mice were on a high fibre diet and most of the extra energy that made them overweight was from the conversion of fibre in to short chain fatty acids.

Simply put, the bacteria from the obese mice implanted into the germ free mice gave the germ free mice the ability to turn fibre into excess energy and caused them to become overweight.

Take Away: Gut bacteria has a huge impact on weight loss. It's also realistically possible to change your gut bacteria with the food you eat.

In Conclusion

Fibre is not an essential part of a healthy human diet. The best studies show the opposite, especially in the context of a low carbohydrate diet.

Fibre has massive implications on the gut microbiome and while there is still much to learn regarding the mechanisms at play when it comes to gut bacteria, it is clear that that the food you eat changes your gut bacteria and therefore impacts your health.