It seems that fibre is always in the news – we never seem to be eating enough of it – but is it really a necessary part of our diet?

Dr Denis Birkitt seemed to think so. He was a missionary surgeon in Africa in the 1940s and studied modern hunter-gatherers. He noticed that they were not getting diseases and he attributed this to the fact that they ate significantly more fibre than Westerners. He suggested that it was protective of the gut – particularly counteracting problems such as diverticulosis (multiple pouches in the colon, caused by weaknesses of the muscle layer in the colon wall) and diverticulitis (when these pouches become inflamed or infected). However, this hypothesis hasn’t necessarily held up, as people often feel WORSE when they add more fibre into their diet. In fact, those with Irritable Bowel Syndrome (IBS) and IBD conditions such as Crohns and Ulcerative Collitis are often told to reduce their intake as excess fibre can exacerbate their symptoms.

So what should we make of this? Let’s take a closer look.

What exactly IS fibre?

It is defined as the indigestible portion of food derived from plants. Some refer to fibre as being divided into two categories; soluble (carbohydrates containing pectin and beta glucans) and insoluble (carbohydrates containing cellulose), although all fibre rich foods contain both. Fibre is found in plant based carbohydrates such as wholegrains, nuts, fruits, fruit skin, vegetables, oats, beans, pulses.

If it is indigestible, how DO we deal with it?

This is where our friendly gut bacteria come into play. The gut bacteria ferment the fibre, turning it into Short-Chain Fatty Acids (SCFAs) butyrate, acetate and propionate. These increase blood flow, muscle activity and water absorption in the colon and also provide food for the bacteria. It is important to note that herbivorous animals, such as cows and sheep, have multiple stomachs and a whole host of bacteria for fermenting the vast amounts of cellulose and fibre that they eat. Humans, however, only have a small amount of these bacteria. Our digestive system is certainly very different from that of a herbivore and is much more similar to a carnivore (who eat little to no carbohydrates). Our colon is not set up for a huge amount of daily fermentation, which is why we can run into problems when we eat too much fibrous food.

Why is fibre deemed so important?

Well it purportedly helps relieve constipation – although ironically it can CAUSE constipation. Fibre bulks up stools, increasing their size, which supposedly helps to make them easier to pass, but this bulk can actually hinder the process of elimination. We are then told to drink plenty of fluids to help soften the stools, but this doesn’t always work in practice.

Fibre slows down the rate of glucose absorption, which is important in those eating a high carbohydrate diet as it helps control blood sugar levels.

It has been suggested that adding plenty of fibre to your diet will help protect you against cancers – particularly colorectal cancer, however in his book “Fibre Menace”, Konstantin Monastyrsky lists many studies which found that, contrary to popular belief, dietary fibre does not protect against colorectal cancer. He states “As you can plainly see from these top notch studies by mainstream researchers and institutions, fibre not only doesn’t offer any protection from colorectal cancer, but potentially elevates the risks”.

Issues with fibre include:

  • Dental cavities – all types of fibre rich foods, with cereals being particularly high on the list, cause dental decay. Bacterial fermentation within the mouth produces lactic acids that bind with the minerals responsible for enamel formation, the weakening of which results in cavities.
  • Diverticulosis and other intestinal issues.
  • Bloating
  • Constipation
  • Flatulence
  • Abdominal pain
  • Loose stools/diarrhoea
  • Weight gain
  • Intestinal blockage – for those with IBD

The SCFAs produced by the gut bacteria ARE beneficial for our health; they boost the protective mucus layer in the gut and help increase motility (the contractions that propel the food through the intestinal tract). Butyrate has an anti-inflammatory effect and it is thought that the SCFAs play an important role in protecting against colon cancer. This makes sense then in the pushing of fibre on us. However, we can take in SCFAs through our diet in foods we CAN digest with our own enzymes via animal sourced foods as opposed to plant-based foods. This cuts out the “middle man” – aka the gut bacteria. These foods are absorbed directly into our bodies and utilised immediately. If you are eating a low carbohydrate diet then the benefits of blood sugar control via fibre intake do not apply.

A common question that is posed to those on a low/no fibre diet is “how do you poop?” The answer is – perfectly well, with no discomfort. Stools are made primarily from water, gut bacteria, dead cells, mineral salts, traces of fat and colouring pigments. When we add a lot of fibre to that you are likely to see undigested pieces of food amongst that (sweetcorn comes to mind!). When we are eating a low carbohydrate diet, proteins and fats are digested by our own enzymes and the nutrients are used in the body leaving little waste behind. This may mean that your bowel movements are less frequent, but that does not equate to constiptation. Constipation is when a stool is hard, bulky and difficult to pass, resulting in straining and possibly to haemorrhoids.

People can end up in a vicious cycle with fibre – suffering with constant intestinal issues, upping their intake and still finding no relief. Many end up taking laxatives on a regular basis, which can interfere with the long term function of the digestive tract and the bowel itself, as it relies on the exogenous help and no longer performs as it should. This can take a long time to reverse. A solution to this problem may be to lower your intake of fibre and carbohydrates generally, and raise your intake of healthy fats. Fat in food releases bile from the gallbladder which in turn stimulates the peristalsis (movement) of the small intestine, and the gastrocolic reflex, pushing the stools along the digestive tract.

Could it have been that the hunter-gatherers that Dr Birkitt was studying were also free of all the modern Westernised foods that are so prevalent in our society today, which would almost certainly have protected them from modern diseases?

On a personal note, since I changed from eating a wide range of fibrous foods, including fermented vegetables to help feed my gut bacteria, I have experienced a really “clean” feeling within my digestive system. I certainly believe that if you are eating fruits and vegetables you will no doubt need to include fermented foods to help keep your gut bacteria in balance, but if you are no longer fermenting all that fibre the gut micro biome will be composed of different strains of bacteria and may no longer be in need of certain types of food.

So, in summary, it would seem that a high carbohydrate diet would benefit from a certain amount of fibre, as a replacement of some of the processed foods, and to slow down the rate of absorption, thereby controlling blood sugar levels. A low carbohydrate diet, however, consisting of adequate animal based proteins and fats,Β would seem to benefit more from low fibre, as the SCFAs are supplied in a highly bio-available way within this protocol, and the minimal “advantages” of fibre may be outweighed by the disadvantages.

What have been YOUR experiences with a high fibre diet?

Please feel free to leave your comments below.