We sometimes hear about fibre as an essential required within our diet, but not many of us actually know the role of fibre in the body. Here I’m going to delve into the importance of including fibre within your diet and how it can improve your health by helping to prevent overeating and enhancing mineral absorption within the body.
What Is Fibre?
Before we discuss the role of fibre in the body, it’d help to know what fibre actually is.
Dietary fibre is a term that is used for plant-based carbohydrates that, unlike other carbohydrates (such as sugars and starch), are not digested in the small intestine and so reaches the large intestine or colon.
So, fibre cannot be obtained from animals, only plant foods.
The Role Of Fibre In The Body
We often hear about how fibre will help to relieve constipation and how it’s found in abundance in fruits and vegetables (another reason to eat lots of vegetables). But fibre isn’t just fibre, there are two forms: soluble fibre and insoluble fibre.
The other interesting thing to note is that fibre has no nutritional value which begs the question, why do we need fibre? The enzymes within the body have no effect on fibre and fibre just passes through the body. However, there are bacteria in your gut, known as gut flora which can actually digest and ferment fibre.
Soluble fibre dissolves in water and thickens the food contents of the stomach. This means food passes through the large intestine at a slower rate, allowing for more nutrients to be absorbed from the digested food which is now mush. For those concerned about blood glucose levels or insulin in the blood, a meal full of soluble fibre will also mean that the rate at which sugar is absorbed from the food in the large intestine is reduced, resulting in lesser blood glucose and insulin spikes.
It may be that because fibre thickens to contents of the stomach, increased fibre intake is inversely correlated with obesity which suggests that for those looking to lose weight, or more accurately lose fat, a high fibre diet could help facilitate that change in body composition.
Don’t forget that since soluble fibre dissolves in water, if you’re eating lots of soluble fibre rich foods, then you may need to increase your water intake to prevent dehydration and keep your body functioning optimally.
Insoluble fibre does not dissolve in water and tends to ‘bulk up’ the contents of our stomach. I’m not quite sure how beneficial insoluble fibre is since it can’t be fermented by gut flora which means no beneficial products are produced. It appears to increase the mass of your stools which if anything could mean your toilet gets blocked and you have some expensive plumbing fees to pay. If you ask me, for optimum digestion, your stools should be composed of mainly bacteria and water – not undigested food which is what insoluble fibre is.
Whilst insoluble fibre is seen as a treatment for constipation, the evidence for it isn’t great. A meta-analysis on fibre in 2012 concluded that “Dietary fibre intake can obviously increase stool frequency in patients with constipation. It does not obviously improve stool consistency, treatment success, laxative use and painful defecation.” All that really means is you’re going to go to the toilet more often, and it’s going to hurt more frequently. Funnily enough, reducing fibre intake was shown to reduce constipation and its symptoms. I suspect since soluble and insoluble fibre weren’t separated in this study, it’s due to the reduced insoluble fibre intake.
That’s not to say insoluble fibre is bad for you – I’m certain that it’s beneficial since it’s found in nature, but I don’t think we need as much of it. If anything, it certainly will help you to pass stools more frequently. However, if you’re prone to diarrhoea or loose stools, you probably want to consume less insoluble fibre.
Fibre And Gut Flora
Much of weight loss information out there is focused around calories in vs calories out. However, I don’t think it’s that simple – the human body is a very complex organism and I believe the health of our gut flora has a large influence on our health and wellbeing.
Our gut flora depend on fermentable fibre aka soluble fibre for food. The gut flora will ferment these soluble fibres and produce various fatty acids such as butyrate, acetate and proprionate which help improve our health. Butyrate has been shown to be quite a useful fatty acid, helping increase insulin sensitivity, reduce inflammation and reduce symptoms of Crohn’s disease.
Gut flora also plays another important role in maintaining a healthy gut. Since these little bacteria in our gut are good for us, by providing food for them, we help them to multiply and grow. This helps them to out-compete any foreign or ‘bad’ bacteria which may appear in the gut so they cannot survive.
How Much Fibre Should I Consume?
How much fibre your body can handle depends a bit on what you do and your exposure to microbes or germs – it’s not a simple answer.
The boy scout who gets his nails dirty often, eats plenty of soluble fibre rich vegetables (unwashed) and isn’t so worried about being clean will have a greater variety of bacteria within his gut flora. This allows him to handle a greater amount of fibre within his diet.
The boy who stays indoors all day, eating processed foods and living off bread and jam sandwiches, constantly cleaning and washing his hands with hand sanitizer will not have a lot of variety within his gut flora.
But that doesn’t mean you can’t eat differently to increase the diversity of your gut flora, but you should adjust your diet gradually. When incorporating more fibre into your diet you can expect to pass more wind, but as your body adapts and your gut flora diversifies, the issue will become less prominent (although I highly doubt it will go away – sorry!) And for those wondering, it’s the soluble fibre which causes the flatulence – this is because the sulphurous gases are produced as byproducts of fermentation by your gut flora.
Sources Of Fibre
You can easily get enough fibre daily by consuming a good portion of cruciferous vegetables at one or two meals throughout the day, but here are some foods containing soluble fibre and insoluble fibre.
Soluble Fibre Foods
- Citrus fruits
- Sweet potatoes
- Brussel sprouts
Insoluble Fibre Foods
- Whole grains
- Fruit (particularly the skin)
Be aware that if you decide to blend these foods to make a veggie or fruit smoothie, you will be losing most of the fibre although you will be consuming the micronutrients from the food.
In Britain daily recommendations for fibre are 30g for adults with the average intake being 18g which suggests the majority of the UK populations needs to try and consume more fibre. Food labelling doesn’t separate fibre into the insoluble and soluble fibre, so rather than worry about which type of fibre you’re consuming, I’d try and consume fibre from a variety of sources.
As compelling as the argument to consume fibre is, people seem to be absolutely fine (and are able to poop without problems) whilst following a meat-based diet. Some people follow it to the extent that they eliminate all plants for a period of time and don’t consume vegetables, fruits, nuts or anything derived from plants.
I think this is certainly an interesting area to delve into and research. The basis of this idea of consuming fewer plant foods is that our ancestor would’ve eaten mostly meat to survive and our brains grew from eating lots of meat. This meant that despite not consuming many plants (only when no animals were available) they were perfectly fine.
One study found that:
A long colonic transit time associates with high microbial richness and is accompanied by a shift in colonic metabolism from carbohydrate fermentation to protein catabolism as reflected by higher urinary levels of potentially deleterious protein-derived metabolites. Additionally, shorter colonic transit time correlates with metabolites possibly reflecting increased renewal of the colonic mucosa. Together, this suggests that a high gut microbial richness does not per se imply a healthy gut microbial ecosystem and points at colonic transit time as a highly important factor to consider in microbiome and metabolomics studies.
What this means it whilst fibre is associated with a long colonic transit time and has shown benefit, a short colonic transit time (which would suggest an absence of fibre in the diet) also has benefits, possibly increased renewal of the colonic mucosa. Altogether this suggests that microbial richness does not imply a healthy gut microbial ecosystem.
If you’re curious, I suggest you go and research it because I think it’s fascinating in the way that it goes against what many of us have been told. I’d advise looking at meatheals.com or carnivoremd.com or mikhailapeterson.com or shawn-baker.com. There isn’t much research on a carnivore diet out there yet, but from what I’ve looked at the evidence is certainly very compelling, especially when it comes to improving metabolic health, losing body fat, reducing autoimmune issues and making people feel great! Anyway, I just thought I’d put the other side of the story out there just so you’re aware!
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