About the author : victoriafenton

I’ve been confronted by (and forced to avoid the confrontation of) a lot of “Zero-carbers” in the last few weeks. To be clear, those who promote “zero-carb” quite literally believe that you need to eat NO carbohydrates at all. This isn’t low-carb. This isn’t even ketogenic (wherein in you can eat as many carbs as you would like to keep you in ketosis and therefore varies from around 20-50 grams, some people reaching 80-100 grams depending on activity levels). This is utterly and completely without carbohydrates.


Wondering what that looks like? Well, clearly that means no bread, pasta, cakes, sugars, honey, maple syrup, fruit, rice, grains at all, pseudo-grains, legumes… but it also means absolutely no vegetables.


According to the zero-carb advocates, all carbohydrates are non-essential. Now, biochemically this science is shaky to say the least… there is no evidence that we thrive without all carbohydrates. There is a legitimate argument that we can, for the most part, run on other fuels such as fats, ketones etc. – but there is remarkably little evidence that we are better off without any carbohydrates whatsoever.

Intriguingly, those who promote the zero-carb lifestyle are not like the ketosis promoters. The ketogenic, very-low-carb dieters are fastidious about mainlining fat bombs and are intent on keeping carbs low enough so as not to raise glucose and insulin levels to knock them out of ketosis. The ZERO-carb dieters are less focussed on maintaining low glucose/insulin and high ketone levels (though this happens by default).


They are instead focussed on the avoidance of carbs because they are adamant that one type of carbohydrate is both unnecessary, and potentially dangerous, damaging and poisonous to the human body. If your mind is heading to gluten (enemy of the nutrition world), or even lectins (read all about how awful they are here) – you’d be wrong. No, the part of normal foodstuff that these zero-carbers feel is the stuff of the devil is… believe it or not… FIBRE.


They claim that the need for any fibre whatsoever is a total myth and that it is a biologically unnecessary component of the human diet. They go so far as to try to make the statement (note: statement, not argument, as they back this with absolutely no hard evidence) that ancestral man lived entirely on fats and proteins and very little (if any) carbs and fibre.

And yet, look elsewhere in the nutrition professionals’ universe and you will find many advocates (from both the conventional Registered Dietician world to the Paleo science promotors and everyone in between) practically claiming that fibre should be re-labelled and officially deemed an “essential nutrient”.

Who is right? And how can two such differing opinions exist about the same component in our foods?


I was tempted to do one of my articles which goes “here’s the basis for this argument, here’s the basis for the other argument… and oh, look! here’s a middle ground (which typically revolves around personalisation)”… And yet, as I began to look into the evidence behind the statements of the zero fibre group… well I found that there quite simply isn’t any. I can’t rubbish and/or evaluate science and evidence which doesn’t exist in the first place…


So, the only actual argument that I found was a variety of renditions of “because I feel better without consuming fibre”, or “my symptoms cleared up and my inflammation dropped when I stopped eating all carbohydrates”. Now, as we know, anecdote is important and case studies are relevant – but in no way does one person’s experience (or even several peoples’ experiences) of being without fibre automatically mean that fibre is any way dangerous or ‘bad for you’.


Going beyond the “I feel better without it” statements to claim that fibre isn’t necessary – at all, for anybody – is an extrapolation and an extension that you simply cannot make.  It’s like someone who is allergic to something stating that that food is therefore terrible for everyone to eat. And this is the point about the low-fibre groups: their statements about the merits (or vagaries) of fibre is more of a reflection of their health, rather than an accurate comment about the nature of fibre itself.

So instead of digging into their non-existent science, I thought it worth pointing out how fabulous fibre can be – and then go on to demonstrate why, and in what circumstances, fibre can problematic… and what to do about those states. And ‘what to do about it’ has precious little to do with removing all fruits and vegetables from your life, forever.


The Science of Fibre – the Ancestral Perspective


Let us first address the ‘ancestral’ argument – as in ‘our prehistoric ancestors didn’t eat many plants’. Phew… well… I am going to defer to better humans than me here. Quite simply put, the ketogenic camp like to claim this too, or at least something similar. They like to claim that hunter-gatherers were frequently in ketosis because they went long days without eating. However, no matter how you string up the science, there are precious few tribes in which this holds true. The very first Loren Cordain investigations into the actual diets of ancestral tribes pitched carb-intake at roughly 22-40%, though they erred on the side of the lower-carb. Later investigations queried the data slightly, but the whole point was that carbohydrate intake varied widely across different tribes. But almost every tribe studied ate the vegetation they came across, with 14% of tribes finding greater than 56-65% of daily calories from vegetation.

When the fibre intake of ancient tribes is analysed there are some who state that some ancestral tribes ate 40-100g of fibre per day, with some reaching 250g … and yet others, quite rightly, state that we’ve really no idea. What does seem clear is that tribal populations ate seasonally – and they did eat what was available. In most cases, though it varied throughout the year, this included plant matter – in fact, most hunter-gatherer diets were ‘strongly plant based’ … ergo, high fibre.

And, it must be pointed out that those in the keto and zero-fibre camps who cite that there were tribes who were no-fibre and no-carb typically highlight the Inuit – holding them up as a paragon of ketogenic virtue. Now, it seems that the Inuit probably were zero-carb – and yet, for reasons of complex biochemistry which Chris Masterjohn beautifully explains here, that doesn’t actually mean they were at all ketogenic. In fact, it’s really hard to make the case that ancient tribes were in ketosis. They may have been temporarily, due to variations in ability to hunt and eat. But the likelihood is that they were mostly consuming diets which meant they were not in ketosis… and not zero fibre or carb at all.

The reality of the hunter-gatherer is that these ancestral men ate what was available and did what they could to maximise the caloric and nutrient density of the nutrition they could obtain. They ate as much as they could from ‘easy’ food to avoid having to constantly be hungry and/or constantly seeking more nutrition. This means that actually as soon as they worked out how to prepare vegetation and grains in ways that rendered the substances non-toxic, they did so. And, moreover, they weren’t avoiding carbs like the plague and labelling anything sweet ‘stuff of the devil’. When they found honey – they ate… all of it. They gorged on it. They knew (and cared) only that it was food, not that it was carbohydrate. There is no way they were doing anything to avoid the carbs and the fibres the found around them. Anything that prevented them having to hunt down a large animal as prey was a victory.


The Science of Fibre – the Modern Perspective

So rendering the ‘ancestry’ argument null and void, what is left to recommend fibre?

Frankly – everything. Fibre is an amazing and vital carbohydrate in our diet and its role in the human digestive system has been linked with countless positive health outcomes and symptom amelioration:


  • Firstly, fibre provides no calories and no nutrients. It’s basically quite indigestible. It is the cell walls and structure of plant matter and isn’t there to provide ‘goodness’, per se – it’s there to keep the shape. We do not have the enzymes to destruct this shape and so fibre passes all the way through our digestive system intact.


  • But that does NOT make it useless – quite the contrary. This means that fibre adds bulk to stools such that the waste products which our bodies need to eliminate are excreted with more ease. But it also provides fuel for something else – the bacteria that live in our guts. Insoluble fibre is typically fermentable by the gut biota and soluble fibre is able to ‘gum up’ with the liquids in our GI tract and create a smooth stool to pass out. Both of these functions are essential to health in the following ways:


  • Fibre fermented by the bacteria ‘gives off’ byproducts. These byproducts are short-chain fatty acids, such as butyric acid, propionic acid and acetic acid. Whilst you may not have heard of these (and ‘acid’ sounds bad), they’re actually really important for the health of the lining of the gut – both the intestinal walls’ cells and the mucosal lining that covers them. These short-chain fatty acids enable us to metabolise and absorb minerals from the food we eat. Essential minerals like magnesium, copper, iron and zinc. Without short-chain fatty acids the result is a weakened mucosal lining of the gut and less absorption of nutrients – which further impacts the resilience and health of the gut and the whole human body.


  • Moreover, keeping our bacteria fed doesn’t just provide us with nutrients and intact gut linings. Our bacterial populations do far more things than just ferment useful byproducts. They signal to the brain through the vagus nerve and enteric nervous system, they regulate metabolism and they also help with digestion of all foods – fibre, protein and other carbs alike. Our microbiome also has a great deal of interaction with our immune system. The studies are too expansive to link to here – but whatever the conclusions we are currently coming to about overall health, it is clear that a healthy microbiome plays a fundamental role. Whilst we aren’t 100% sold on precisely what makes the healthiest of gut biomes, having the bacteria present requires feeding them. And this requires fibre.


  • Beyond the bacterial impacts and the mechanism – the data surrounding fibre and health outcomes is compelling. Fibre has been shown to reduce the risk of cancers (including, perhaps obviously, colorectal cancer but also liver and pancreatic cancers). Fibre-rich diets have been linked to lowering the risk of heart disease and also lowering overall inflammation levels. Diabetic patients with high fibre diets have lower risks of mortality. Fibre is being preliminarily studied as a quantitative reducer of inflammation – i.e. the higher the fibre, the lower the inflammation. If this is true, the zero-fibre advocates who believe they are ‘saving’ themselves from a rollercoaster of blood sugars (detrimental for many reasons, one of which being because this is highly inflammatory) are actually shooting themselves in the foot by exponentially increasing their inflammation burden.


  • And whilst we’re on the topic of insulin/sugar consumption and eating behaviours – fibre also influences GLP1, or Glucagon-Like-Peptide 1. This is an insulin-independent regulator of hunger, fullness and eating behaviour that tells the hypothalamus in our brain when we are satiated and reduces food and water intake. It also slows gastric emptying, keeping us – as all the weight-loss/appetite-regulation diets would promote – ‘fuller for longer’. Fibre is one of those foods, therefore, that can be highly satiating and turn down any signal to eat. It seems to me that the no-carbers promote fats and proteins as highly satiating foods. However, what they miss here is that whilst proteins and fats are very satiating, they also carry many calories within them. The satiety levels from fat and protein are a lot to do with the fact that (surprise, surprise) you’ve eaten a lot of calories. Eating fibre, however, can signal fullness and slow digestive transit… and yet, there are no bioavailable calories in it.


In a population concerned with appetite and glucose regulation (i.e. the ‘zero-carb’ advocates), it seems that eating a relatively low calorie, fullness-promoting, bowel-helping, health-outcome-improving vegetable would be a really, really good idea. Or indeed… lots of them. And yet, in the lunacy that is modern nutritional dogma, it seems that these people just don’t see it this way.

So Why Are The Low-Fibre (Zero Carb) Converts So Anti?


As I look into the “I feel better” comments which surround the zero-carb advocates it is easy to see that it is the very effects listed above – the modulation of the microbiome, the production of short-chain fatty acids, the feeding of bacteria and adding bulk and roughage to the stool – that are aggravating and affecting those who don’t get on well with fibre, subjectively. And I’ll grant them this – it’s not easy to be bowled over by the long term positive health outcomes (reduced cancer rates, anyone?!) when eating fibre subjectively (and relatively immediately) gives rise to symptoms of bloating, pain, distention and systemic inflammation. Because yes, in those with unhealthy and permeable gut environments eating the fibre which creates fermentation in the digestive tract really can create both localised intestinal symptoms but also widespread inflammatory issues and immune flares which can feel painful and damaging to the person experiencing them.


And yet, far from the fibre being the issue, the problem (as always) lies with the nature and the health of the digestive systems of those who feel better without fibre.


When a state of dysbiosis or digestive distress is already in play, adding fibre is going to fuel that situation. If that digestive system is in disarray, fibre is going to just make that state much worse because it just exacerbates things. If any level of intestinal permeability is coupled with an immune activation and dysbiosis is occurring, piling in the very food which feeds the dysbiotic flora is like lighting the blue touch paper – the natural physiological response is the alarm bells of pain, inflammation and immune flares. So, to be totally clear, I completely believe and understand those who say that being without fibre is a much more comfortable state for them. And yet, the solution that I arrive at, as a Functional Medicine practitioner (interested in resolving root causes rather than promoting avoidance as a means of treatment) is very different from that of those who believe in the ‘zero-fibre’ approach.


Instead, you have to work out what the situation is within the digestive tract and resolve it. Then you can resume the consumption of the ludicrously healthy fibre after first having corrected the imbalance and immune sensitivity which was dominating the health picture.


So now, having a digestive and bacterial situation that could do with some work simply does not render the fibre that aggravates it inherently “bad” or “unnecessary”. And the irony is that the “work” that this digestive and bacterial situation requires may well involve a period of time on a Low-FODMAP diet, which is, by definition, low fibre.


The Benefits of Low Fibre


FODMAPs are fermentable carbohydrates. This isn’t just fibres, it’s everything in the fruits and vegetables (and also grains, legumes, dairy etc.) that can be fermented by bacteria within the gut. However, fibres in foods are fermentable (as well as the sugars in things like milk and fruits) and so a low-FODMAP approach is automatically low in fibre. Again, the diet is literally called “low”-FODMAP, which doesn’t ever indicate complete removal of all fibrous foods. However, following this approach where fibre is restricted for a short period of time has been shown to have remarkable effects on minimising the symptoms of those with inflammatory and irritable bowel conditions. It has also been shown to regenerate the hormone producing cells of the gut (the endocrine cells of the large intestine) which, in turn, improves motility and the sensations within the GI tract. This is, of course, a great therapeutic tool.


But a therapeutic tool in nutrition is, as with medication, a short-term intervention which is designed to refresh and reset the body. It is never intended to be a long-term end point – particularly in the extreme recommended by the low fibre advocates.


Just to be completely clear, the studies that I have cited above are on low-FODMAP diets – NOT zero-carb ones. This means that there is absolutely and categorically no evidence to suggest that the zero-carb approach, and the extreme limitations that it promotes, are at all necessary, or provide any added benefit to a low-FODMAP approach as studied above.


The Perils of Zero Fibre


The benefits of low-FODMAP in the short term may result in an eventual diet that might limit one or two poorly tolerated vegetables or fibrous foods, which will of course be highly specific to each individual patient and the state of their health at any given time. And yet this short-term intervention is designed to right the ship that has gone off course, not be a permanent state for the rest of your life.

The reason low-FODMAP diets aren’t recommended long term is because when you remove fermentable carbohydrates you remove a lot of really healthy foods. What’s worse is that if you follow the ‘no carb, ‘no fibre’ approach you don’t just lose out on fibre’s benefits:


Having zero fibre completely eliminates all fruits and vegetables from your life. Whilst a few toddlers might be absolutely delighted at this, vegetables are a fundamental pillar of health.


This is shown by the improvement in health outcomes across the board as the quantity of vegetables eaten increases. The more portions of vegetables you eat per day, the healthier populations are, overall. As with fibre in the reduction of inflammation – this is a dose-response relationship.


Simply put – your overall ealth is directly proportional to the amount of vegetables that you eat.


And the reasons for this aren’t singular. Instead, they are multifaceted and have everything to do with the plethora of antioxidants, polyphenols, phytonutrients (think carotenoids, flavonoids, isothiocynates, sulfurous compounds etc. etc) and vitamins and minerals that are found in vegetables. And whilst some of the vitamins and minerals may be found elsewhere… nowhere are they more concentrated, bioavailable, densely present and with such varied concentrations (all in the perfect biological ratios) as they are in plant matter. Cutting plant matter out of your life is like severing a relationship with the products in the world that could help you most.

There will always be some vegetables that you don’t get on with, some that you don’t like even (sprouts, anyone?). And the bitterness in cruciferous or sulphurous veg might be too much for the younger palate or the super-tasters among us. But to eliminate fibre – to cut out all carbs – out of some false ideology that they are ‘unnecessary’ and some subjective evidence that you ‘feel better’ without them is, in my opinion, an utter fallacy. And, honestly, fairly lazy investigation into health outcomes.

There are a lot of fad diets out there, and I’m achingly aware that it’s now going to be Christmas (where nobody wants to consult someone like me because they’re frightened I’ll take their ‘Christmas indulgences’ away) and then soon it’ll be January… where the fad diets are going to be so, so attractive to those wishing to ‘get back on track’, or – worse – ‘atone’ for their Christmas deviances.

implore you… please don’t fall for it. Enjoy your Christmas – indulge without guilt. And if, come January, you feel attracted to a healthier lifestyle and diet – find one which is balanced, moderate and founded in actual science. And if you, or those you care about, genuinely do feel ‘better’ without fibre or carbs… please seek the help of someone like me who can investigate why your biochemistry is reacting this way – and help you fix it, not just face the avoidance of fibre … forever.

Extremes are rarely necessary – and if they are, they are only indicated for a short time. If you’d like to reach out to me to discuss your health concerns and whether anything ‘extreme’ is indicated in your case, get in touch with me today.

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