Updated: Dec 13, 2021
Like it or not we all have a "Large Intestine" aka colon, aka hind gut; a fact that doesn't sit easily with some modern food trends and choices (carnivorous). As the name implies it is large and its behaviour or misbehaviour plays a large part in our daily activities. There is an apparent epidemic of a variety of gut complaints and most of the symptoms are related to hind gut dysfunction. Discussions of these things are rife on social media where all sorts of elimination diets, self-medication and lifestyle modifications are being tried. The symptoms are varied as are the assumed diagnoses. Common symptoms are pain, bloating, gas retention, and alternating episodes of constipation and diarrhoea. Assumed diagnoses are all sorts of food intolerances for which the most commonly blamed are wheat and gluten. "Leaky Gut" generates 3.5 million hits on Google. Another epidemic diagnosis is SIBO (small intestinal bacterial overgrowth, 6 million hits on Google) which is associated with increased bloating and pain soon after a meal. Also epidemic is Irritable bowel syndrome (IBS) diagnosed by symptoms of colicky pain and diarrhoea alternating with constipation and is estimated to affect 20% of the world population. All of these things have been increasing over recent decades and they are also increasing in developing countries experiencing Westernization trends. A much more serious condition of Inflammatory Bowel Disease (IBD) is increasing as well especially in younger subjects. In fact IBD is 16 times more common in those with IBS and tends to occur 2 to 3 years following symptoms of IBS. More serious still, colo-rectal cancer is also increasing in younger people and is far more common in those experiencing IBS.
In order to get something to work right there's no short cut to understanding as much of the biological and evolutionary details as possible. Generally speaking, the job of the small intestine (SI) is digestion and the job of the large intestine (LI) is fermentation. What doesn't get digested and absorbed in the SI passes through a no return valve into the LI. Like it or not, you have no choice, the LI will be colonized by a huge amount and variety of microbes, collectively called your microbiome. The material that passes through the valve into the LI determines what grows, according to the tenet "Everything is everywhere but substrate and environment selects" so to a large extent, diet can control your microbiome. Dysbiosis is the term given to an unhealthy microbiome and has been found in all of the gut disorders, more on this later.
Mind boggling facts about your gut!
The surface area of the gut lining is the size of a tennis court and it renews itself every week. Half a million gut lining cells are replaced every second generated from intestinal stem cells and the dying cells are removed by specialist intestinal macrophages (Latin for big eaters) that swallow, digest and recycle cell residue at lightning speed. Distinct from macrophages elsewhere in the body, intestinal macrophages are also short lived with a life cycle of around 3 weeks and in turn are consumed by newer macrophages. The point to be made here is that gut function and immune function are inseparable, interdependent and incredibly dynamic. Dying cells are instantly consumed by macrophages and inefficiency of this process leads to accumulation of necrotic cell residue which is highly inflammatory and contributes to symptoms of IBS and the risk of more serious inflammatory bowel diseases and cancer.
So over 500,000 gut lining cells and immune cells are created per second from stem cells while a roughly equal number dying cells must be recycled in order to maintain a steady state (homeostasis). The preferred energy for this huge effort is the short chain fatty acid, butyrate and cells become severely energy stressed in its absence. Butyrate is also necessary to program the special anti-inflammatory regulatory T cells and anti-inflammatory nature of intestinal macrophages which must efficiently digest and recycle the hundreds of thousands of expired cells every second as well as the task usually associated with phagocytes: tracking down and engulfing invading microbes.
What is Dysbiosis and how to create a healthy Microbiome?
Dysbiosis is the term given to an unhealthy community of gut microbes but whatever the permutation the common denominator boils down to a depletion of the microbes that make butyrate. According to "Everything is everywhere but environment selects" the substrate for SCFA producing microbes is "fibre" and the environment for butyrogenic bacteria is an acidic one.
For our purposes, let's assume "fibre" is all of the plant material that escapes digestion in the small intestine and passes through to the large intestine, which is where a community of hundreds of different microbes thrive from living off fibre. Collectively called the microbiome, these microbes multiply dependent on the amount of fibre available, and produce nutrients including vitamins for the survival of their host animals. The world's most important macronutrients supporting plant eaters at the base of the whole animal food chain are short chain fatty acids (SCFA) produced from microbial fermentation of fibre. Acetic acid (Latin for vinegar) is the most plentiful SCFA and it creates an acidic environment in the large intestine which suppresses harmful bacteria and greatly increases activity of symbiotic microbes that produce other SCFAs such as butyric acid and propionic acid. The importance of the acidic environment of the large intestine should not be underestimated, the concentration of hydrogen ions is 1,000 times higher (pH 5.5 v 7.5) with adequate fibre v low fibre diet. The acetic acid environment suppresses dysbiotic microbes and is substrate for symbiotic ones to produce large amounts of the vitally important butyric acid (aka butyrate) to support energy requirements and cell signalling directed to the cells of the gut and immune system.
In addition to numerous other actions butyrate regulates intestinal permeability by increasing hormones (GLP1 & 2) that are involved in controlling the gut barrier. Furthermore, the cell signalling role of butyrate guides the differentiation of intestinal stem cells into their many different functional cell types and promotes mucus production, an important component of the gut barrier. The Leaky Gut phenomenon is very common with junk food/fibre deficient diets and toxic gut material entering the blood stream leads to chronic inflammation and abnormally severe immune reactions to respiratory infections such as COVID19 and flu.
As with all epidemics there has to be a novel common cause such as a new infection or an environmental or behavioural change. I believe the “Fibre Gap” is the most likely explanation for the epidemic of gut disorders and there is a lot of evidence why this might be so. The progressive deficiency of fibre from the Western diets is an undisputed concern. Barely 5% of the population actually achieves the recommended daily amounts of 24 to 30g a day, which is most likely much less than the optimal amount anyway as our hunter gatherer ancestors consumed 100 to 200 g/day.
No Gas No Gain
Microbes have enzymes that breakdown fibre to glucose and microbes use glucose as an energy source. In the absence of oxygen such as the situation in the contents of the hind gut, microbes produce hydrogen, carbon dioxide, acetic acid, butyrate and other organic acids.
As you can see from the equation one glucose molecule has the potential to produce of lot of gas. So, let’s clear up this issue of gas being a bad thing, on the contrary producing gas is essential for a healthy gut. Another thing, hydrogen has anti-oxidant and cell signalling properties and is gaining popularity as a medical treatment for all sorts of inflammatory conditions. However, gas production can be a problem on top of sluggish gut motility, or a blockage caused by constipation. Here lies the conundrum, the cure for these gut disorders usually increases the severity of the symptoms before it can improve them. But a low fibre or low FODMAP diet is probably the worst thing you can do in the long run. Best introduce and increase fibre and prebiotics gradually if they make your symptoms worse initially.
It is important to promote knowledge of the importance of BUTYRATE to the structure, function and health of the colon (aka: hind gut, large intestine) as well as muscle strength, health promoting effects in other organs and tissues in the body, including the brain.
IBS, IBD, SIBO and Leaky Gut are increasing problems and may lead to serious illness. Fibre/prebiotic deficiency is a fact. Fibre was considered nonessential nutrients in the past, is now considered to be necessary to maintain an optimally functioning gut, adequate levels of immunity and suppress inflammatory and allergic responses. Best first step to try is fix your fibre gap but stick with it as the symptoms might get worse before they get better. Oh and yes, we need to be more understanding of intestinal gas. It is not a disease.