health fibre

What’s the Deal with Fibre?

You are what you eat, we all know that.

But more accurately, you are what (a) you assimilate and (b) what your gut flora eat, and if your gut flora are in tip-top condition, you will digest and assimilate your food well.  It all comes down to the quality and diversity of the strains of healthy bacteria which live in your digestive tract.  We are alive with organisms, more than 100 trillion in fact, which live in our mouths, on our skin, in our gut and all over our bodies outnumbering our cells 10 to 1.  This makes you 9/10ths bacteria and one tenth “you”.  We depend on these microbes for life itself, for energy, to provide us with extra genes, offer protection from germs and viruses, improve digestion and make important substances and nutrients for us as well.  These beneficial microbes – so essential to life – provide extra genes which outnumber ours by a factor of 100 to one. Collectively, these organisms are called the microbiome, an intriguing and complex ecosystem that feeds on fibre. So it makes perfect sense to consider carefully the food we feed this colony of life-giving microbes comprised of thousands of species so that they can keep us healthy.

One of the most important and critical types of food the gut microbiome thrive on is fibre.  When these microbes are starved for the right food and too little fibre, they are not able to support your health the way they should.  It’s unfortunate that there is a move in some circles declaring fibre unimportant to human health because nothing could be further from the truth.  Key fibres are the “workhorses” for maintaining a healthy gut microbiome.  Fibre is not just there to get the bowels working more efficiently although that’s an important part of its function, they do so much more.  The meal of choice for your gut bacteria happens to be fibre, you don’t digest it, they do.  Some studies show that more fibre enables more effortless weight loss which is a happy finding.  But without fibre, the beneficial bacteria are forced to feed on the protective mucus lining of the intestines, with possible serious inflammatory consequences.  Fibre is very important in the human diet.

Change your microbiome – change your state of health

We’ve established that fibre is an integral part of good health, but not just any fibre.  The sort of fibre we are looking at is the fermentable fibre from vegetables and nuts primarily – fibres which arrive in the large intestine intact, ready for digestion by armies of microbial species.  They get to work digesting the fibre providing us with extra energy, nutrients, short-chain fatty acids, some B vitamins and dozens of other beneficial elements. These complex compounds improve immunity, decrease inflammation throughout the body and even protect against obesity, offering us health in every area of our physical lives.  To think fibre is unnecessary is to ignore powerful scientific evidence to the contrary.

The type of fibre you do not want is derived from grains.  These are fibres which may lacerate the sides of the colon, they could be GMO, sprayed, hybridised and toxic to the body. Who remembers the bran phase of the 1980s? Right idea, wrong fibre.  I personally know people it caused more problems than solutions for.

The Western diet is particularly low in fibre providing only around 15g of fibre a day, whereas if you lived 100 years ago you would consume closer to 10 times more. In fact eating just 21g more fibre a day for 3 weeks can swing your bacterial concentration of the number of Bacteriodetes bacteria and decrease the number of Firmicutes offering a more positive ratio which could determine whether you are going to be overweight or lean.  We’ve known for ages that a higher fibre diet shifts more weight, and there are studies to prove it1, but since the microbiome project some years ago, we didn’t realise the role the various species played in determining our weight.

By starving beneficial flora, some species will die off, compromising the immune system, and allowing more harmful opportunistic bacteria to take their place. The good bacteria then have to resort to feeding off the mucus lining, which is really not a good idea.  In a rodent study2, researchers found that mice fed fibre-free food had a dramatically diminished mucus layer in their previously healthy gut lining.  Another study showed that the lack of fibre allowed unhealthy bacteria to penetrate the lining of the intestines, causing ulcerative colitis.  The lining of your gut is crucial to your state of health. Researchers have found that a high fibre diet is essential to maintain bowel health.  The good news here means that reverting to a high fibre diet quite quickly improves beneficial bacteria species, but needs to be maintained on a daily basis for the best results.

Japanese researchers discovered that butyrate – an anti-inflammatory compound produced by fermentable fibre in the gut – greatly improved T regulatory cell production.  These cells are responsible for maintaining a healthy immune system – most people with auto-immune disease have reduced T regulatory cell function, proving that gut bacteria have a direct effect on the immune system. As 80% of our immune system is located in the area of our gut this should come as no surprise.  This butyrate, a short chain fatty acid, is also the food of choice for the cells lining the colon so these cells depend on the bacteria to change the fibre into their preferred form of food.  A poorly fed colon lining results in the leaky gut syndrome where unwanted food products and toxins can literally leak from the colon into the blood and cause malaise of one sort or another throughout the body.

What kind of Fibre?

Different types and groups of fibre produce different species of bacteria.  For example people who eat a lot of grains appear to have unusually high levels of bacteria called Prevotella, as has been noted in both Burkina Faso and in South Africa (both high grain-consuming countries). This strain has been associated with HIV, and although it’s clearly not the cause, it is noted that HIV patients have unusually high levels of this group of bacteria.  Could it be possible that this type of bacteria makes it easier to contract HIV? We don’t know, it’s merely an observation. But Prevotella has also been associated with autism, rheumatoid arthritis and general inflammatory conditions, and I submit that this could be due to the damaging effects of grains not only on the body, but particularly to the gut bacteria.  It makes sense that particular types of fibres affect bacteria which in turn compromise or strengthen immunity.

Resistant starch (RS) is fast becoming thought of as a type of fibre, and last issue had an article on that so we won’t cover it here.  Soluble fibre such as that found in psyllium husks, as well as RS, both encourage different strains of bacteria to bloom. By depriving your gut of fibre you starve the healthy bacteria if they have nothing to eat, they will begin to eat the mucus lining of your colon, which will compromise your health. Very often we discard important parts of the plant which offer us superior fibre, for example the hard root part of the asparagus spear is often snapped off and thrown away as it’s harder than the soft tip.  But this type of fibre is very good at providing a specific kind of bacteria called Ruminococcus (found in grass-eating animals like cows and game), and which in turn has a wonderful role to play in our colons. So don’t eschew vegetable fibres, eat more of the fibrous veggies in order to feed your healthy gut bacteria.

The colon needs to be extremely acidic, and getting the right kinds of fibre will produce the correct pH for the compounds to be formed by the fibre and bacteria.  Opportunistic bacteria are pH sensitive therefore maintaining the correct acidity (do not alkalanise yourself as many fads would have you believe is healthy) is an important key to good bowel health.  The bowel remains acidic as it ferments specialised fibre, and these fermentable fibres provide the various species with the food it needs to perform optimally, guarding the lining of the colon and producing healthy bowel movements.

Types of fibre

Soluble vs Insoluble:

Insoluble passes through the body unchanged and doesn’t get absorbed. Adding neither calories nor carbs to the diet just volume. Soluble fibre is the kind which sometimes forms a gel (psyllium, parts of the flaxseed and chia which have both kinds of fibre) and this adds a few calories but no carbs to the diet. Soluble fibre is fermented to short-chain fatty acids, acetate, butyrate and propionate. All shown to promote satiety, reduce the amount of food you eat and help with weight loss.

If your diet is too low in fibre consider adding in psyllium husks, grinding up some flaxseeds and increasing your fibrous vegetable intake. Perhaps even a little resistant starch now and then.

Unfortunately most of the highest fibre foods are those we don’t eat as LCHF disciples.

However here are some ways to add more fibre to your food:

  • 3g per medium artichoke (cooked)
  • ½ an Avocado 6.7-9g
  • Broccoli 5.1g (1 cup cooked)
  • Brussels Sprouts 4.3 (1 cup cooked)
  • Boiled green leafy veg provide a whopping 5g per cup
  • Berries are up around 8g a cup
  • Cabbage 4g a cup, cooked
  • Chia seeds 5.5g per tablespoon
  • Flaxseed meal (make this yourself) – 2 tablespoons contain 3.8g fibre
  • Green beans 17g per cup, cooked
  • Kohlrabi raw 1 cup 5g
  • Kale 3g 1 cup raw
  • Nuts and seeds are relatively high at around 2.7-just on 4g per 28g
  • Add psyllium husks if all else fails.
  • Onions and garlic are good ways to feed flora, and have some fibre, add to food for taste.

Remember just as you need to eat good food daily to remain healthy, so your flora need daily feeding with fibre to remain at a healthy level.


Prebiotic fibre is like an “instigator” in that it stimulates good bacteria to colonise the gut while providing it with food.  Good prebiotic fibres are found in onions, garlic, Jerusalem artichokes, chicory, asparagus and dandelion greens.  Drink lots of water which helps to swell the fibre so it can do its job.

Things that adversely affect this delicate microbiome are all the foods we recommend against in LCHF: sugar, grains, processed food, inflammatory foods, seed and grain oils – these cause damage and death to the microbiome and sabotage your best efforts.

So what about fibre on a low carbohydrate diet?

I listened to a podcast by Chris Kresser some time ago, where he remarked on how those on a very low carbohydrate diet (which means I imagine that they were having very little vegetable matter and thus fermentable fibre) showed signs of a rather too-alkaline pH in their stool samples. This meaning their colons were too alkaline. Those having only around 40g carbs a day or less had low levels of the protective substance butyrate, their pH was too alkaline and many even had indications of dysbiosis. Remaining on a ketogenic diet for too long (unless you are a chronic diabetic) may be giving you too little fibre in the diet with ‘gut-wrenching’ consequences. If you are in this position, consider adding in psyllium husks and concentrating more on the fibrous vegetables. Extreme carb restriction may also restrict fibre intake which will compromise the health of the colon and limit levels of good bacteria.

Going too low carb will automatically drop not only the quantity of fibre, but the diversity obtained from a variety of vegetables.  Unfortunately very few studies or trials have been done on fibre and the microbiome thus far, but that is changing. USA’s Dr Chris Kresser is conducting huge clinical studies at the moment in this regard. So hopefully we will have some data in the not too distant future. The ridiculous notion that we need less fibre rather than more is rejected by the top experts in the LCHF field. Dr Jason Fung of Canada is dogmatic on the essential role of a high fibre diet. Fibre is crucial for maintaining blood sugar control and guarding against insulin resistance.  And of course fibre feeds the microbiome – the most important function of all.

Published with permission from the article by Sally-Ann Creed for Lose It Magazine, Volume 9 2015




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Originally published on on 22 January 2018.

Instagram: @SallyAnn_Creed

Facebook: @SallyAnnCreedSA

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