Short-chain fatty acids (SCFA’s) are the result of fermentation of dietary fibres, also known as the soluble fibre in our colon. Our colonic bacteria are responsible for this and as many studies have shown, SCFA’s have a tremendous effect on our gut health and overall wellbeing. More importantly, it is becoming more and more evident, how high plant-based diet, high in fibre is beneficial for metabolic syndrome and its comorbidities.
What is fibre?
Most foods contain both insoluble and soluble fibre but only one is usually in abundance. Both types come from plants and are forms of carbohydrates.
The difference between fibre and other carbohydrates lies in where it is digested and used up.
While most carbohydrates are gradually broken down to glucose and absorbed in the small intestine, fibre travels all the way to the colon, where it is fermented by your colonic microorganisms.
Soluble vs. insoluble
Soluble fibre absorbs water, turning into a gel-like mush supporting digestion in a number of ways, as it can slow down things in the digestive tract (helpful during diarrhoea).
On the other hand, insoluble fibre does not absorb water and is not fermented or broken down by colonic bacteria and therefore it speeds things up, alleviating constipation as it adds bulk.
From fibre to short-chain fatty acid
As the soluble fibre cannot be digested in our stomach or the small intestine, it becomes available for microbial fermentation by the bacteria in the colon.
The main metabolites produced are SCFA’s including acetate, propionate and butyrate along with hydrogen and even CO2. Some of the Firmicutes bacteria are strongly abundant in the fermentation of butyrate in the colon; these include Faecalibacterium prausnitzii, Eubacterium rectal and Eubacterium hallii.
Lactate isn’t an SCFA but it is produced by some bacteria occupying microbiota such as Bifidobacteria and Proteobacteria. However, lactate can be successfully transferred by Eubacterium hallii and other species to form SCFA.
The SCFA’s abundance
The most abundant SCFA is acetate, accounting for around 60 to 75% of the SCFA. Propionate is a gluconeogenic metabolite, mainly formed in the liver accounting for around 25% and butyrate seems to be the least abundant being as low as 15%.
However, when it comes to possible health interventions, butyrate and propionate demonstrate the strongest evidence, although further research is required in this area.
Butyrate seems to be the preferred fuel for the colonic wall and a responsible metabolite for observed protection of the colon, consequently stimulating numerous cellular processes. Elevated butyrate formation has been established to influence epithelial cell proliferation, apoptosis and differentiation.
Disorders associated with visceral hypersensitivities such as IBS and ulcerative colitis which develop due to systemic inflammation of the colon have offered significant improvements with the presence of butyrate.
This protective mechanism of butyrate composed of a high fibre diet also seems to play a positive metabolic effect against Type 2 diabetes and cardiovascular diseases, two conditions related to the increasing incidence of metabolic syndrome.
Metabolic syndrome and related comorbidities
The recent sedentary lifestyle, along with excessive overeating of energy-dense foods worldwide, has created an epidemic of 1.9 billion (2016) overweight and obese citizens who are currently at increased risk of cardiovascular diseases, musculoskeletal disorders and a step closer to developing certain types of cancers.
The good thing is we are slowly transitioning from blaming the individual for their increased weight and are starting to consider where the real problem lies.
Look at it this way, if you have a class of 30 students and one student is failing, you would automatically look at that student and consider possible options of why he is failing. But imagine this, you have a class of 30 students but now 20 of them are failing. The focus immediately shifts away from the students and rather towards the teacher.
And this idea can be also applied for our obese population. The world population is estimated to be 7.6 billion, and 1.9 billion are overweight or obese.
It’s not about the individual anymore but their surroundings. It’s the social media, the large chain food industries, it’s the fact that our environment became obsessed with forcing calories down our throats on every corner, every TV ad, every billboard, every supermarket, every fast food chain.
Elimination of obesity
Thankfully, their tactic is unsustainable and couldn’t be more unhealthy. It will lead to a crisis which will put an end to all this nonsense.
Eliminating obesity, a fully preventable disease, along with its life-threatening health complications, by investing in improving communities and promoting healthier choices in life has become of great importance.
There are plenty of sources providing strong evidence to suggest that diet is one of the most important and most effective modulators in the formation of a healthy balanced microbiota.
But why all the fuss about healthy balanced microbiota?
The colonisation of bacteria in a study based on different diets showed a positive correlation with increased fermentation rate in the colon during a specific non-starch polysaccharide diet. Non-starch polysaccharide diet is a complex diet composed of cellulose, pectins and hemicelluloses.
Out of the three SCFA, propionate was associated with an increased number of Bacteroidetes caused by inter-individual variation. This provides clear evidence that alterations in the diet have an impact on the human microbiota.
Furthermore, diets high in non-digestible carbohydrates such as galactooligosaccharides lead to an advantage modification of the microbiota by decreasing the colonisation of the gram-negative bacteria to increased colonisation of beneficial gram-positive Bifidobacteria in overweight adults presenting characteristics of the metabolic syndrome.
A recent American study concluded that high consumption of whole-grain wheat is associated with increased colonisation of Bacteroidetes and Firmicutes but reduced number of Clostridium.
This evidence suggests a considerably reduced risk of developing chronic diseases, especially cardiovascular diseases, diabetes and cancer, which interestingly are all states that robustly relate towards today’s unacceptable weight gain among the population.
Overall, foods with a low glycaemic index and whole-grain diets support colonic fermentation, which subsequently stimulates greater production of SCFA’s.
Increased plasma levels especially of butyrate determined beneficial prevention and possible treatment for some of the metabolic syndrome comorbidities, including type 2 diabetes and cardiovascular diseases.
The ecosystem within us
In summary, the human microbiota is an ecological community of commensals, an ecosystem that requires a constant equilibrium between bacteria living in the human colon. This symbiosis has a pivotal role in maintaining a healthy colon which strongly influences a person’s entire health.
However, to maintain this healthy symbiotic environment we have to regularly nourish it nutritionally from our diet and other forms such as lifestyle and healthy environment.
EAT. YOUR. FIBRE.