Last week we introduced the concepts of pre-biotics – the food for our gut microflora; pro-biotics – the actual micro-organisms; and then the post-biotics which are the bioactive substances which are produced by those micro-organisms that are so beneficial to our bodies.
Here is a very detailed article about the role of short-chain fatty acids (SCFA) in health and disease: (The full article is available on the web – actually a chapter in a book).
Here are few quotations from the introduction:
“There is now an abundance of evidence to show that short-chain fatty acids (SCFAs) play an important role in the maintenance of health and the development of disease.” “SCFAs have been shown to alter chemotaxis and phagocytosis; induce reactive oxygen species (ROS); change cell proliferation and function; have anti-inflammatory, antitumorigenic, and antimicrobial effects; and alter gut integrity. These findings highlight the role of SCFAs as a major player in the maintenance of gut and immune homeostasis. Given the vast effects of SCFAs, and that their levels are regulated by diet, they provide a new basis to explain the increased prevalence of inflammatory disease in Westernized countries, as highlighted in this chapter.”
The detailed biochemical mechanisms are beyond the scope of this short article, but I will mention a few of the highlights.
Indeed SCFAs or their deficiency may affect the pathogenesis (mechanisms of disease production) of a diverse range of diseases, from allergies and asthma to cancers, autoimmune diseases, metabolic diseases (such as diabetes, high blood pressure, high cholesterol, etc), and neurological diseases.
The three main SCFAs are acetate, propionate and butyrate. These each have higher concentrations within different parts of the large intestine, and have different beneficial effects on the body. Interesting is that different species of bacteria are more likely to produce one kind than others, and so imbalance in the bacterial diversity may affect the benefits of the balance in different SCFAs.
This balance can also be affected by the amount and variety of different dietary fibres upon which the bacteria feed. It has been shown that the composition of the gut microbiota can change within as little as a day of dietary changes. The typical Western processed diet has a very low fibre content, which means most nutrients are absorbed in the small intestine leaving very few substrates (fibre food) for the colonic bacteria.
This results in dysbiosis (imbalance in the normal environment of the colon) leading to increased susceptibility to inflammatory diseases such as inflammatory bowel disease (ulcerative colitis, spastic colon and colon cancer).
Butyrate and propionate have been shown to suppress genes responsible for the growth of cancers such as colon cancer – and may be the reason a high fibre diet is protective against this form of cancer.
Acetate has been shown to suppress excessive inflammatory responses and thus have a general calming effect upon inflammation within the body. Another benefit shown from SCFAs is the suppression of preterm labour, and colitis and arthritis in mice models. Some studies suggest SCFAs may reduce appetite through stimulation of leptin release from fat cells.
Other studies suggest a mechanism for the lowering of free fatty acids (LDL is a transporter of free fatty acids in the blood – a commonly elevated lipoprotein in people with cardio-vascular disease). Butyrate is a major source of energy for the cells lining the colon (colonocytes); they also dictate colon mobility, colonic blood flow and the pH of bowel contents, which affects absorption of electrolytes and nutrients.
Another vital function of SCFAs is to improve the integrity of the intestinal wall by improving the mucus layer, increasing cell wall survival, and improving the tight wall junctions between cells. We spoke a few weeks ago about leaky gut syndrome, or increased gut permeability, which may well be caused by a lack of SCFAs related to poor fibre intake and/or inadequate diversity of the microflora.
Surprisingly, SCFAs also express anti-microbial effects. Check the ingredients in bread, and you will more than likely find propionate there as a preservative (because of its antimicrobial effects). It is unknown how SCFAs can affect the diversity of the microbiome.
Studies of the microbiome of people who suffer from ulcerative colitis and Crohn’s disease have shown dysbiosis (abnormal spectrum of micro-organisms).
One of the experimental treatments is the give a faecal transplant – from a healthy individual. This has shown dramatic benefits in some people, confirming the theory that these conditions may be due to a poor spectrum of micro-flora.
Studies have also shown that people who suffer from type-1 Diabetes, as well as rheumatoid arthritis have deficiencies in certain bacteria responsible for producing high levels of SCFAs. Another finding is that children with allergies and airway inflammation are deficient in SCFAs.
According to Dr Wil Bulsiewicz, research is finding other more distant benefits of SCFAs – for instance butyrate enhances the integrity of the blood/brain barrier, preventing toxins and unwanted chemicals from entering the vital brain substance. It has been shown to reduce the “brain fog” associated with poor lifestyle behaviours, and has been suggested to prevent dementia and other degenerative diseases of the brain in the long term.
In summary
Short Chain Fatty Acids which are primarily produced by colonic bacteria are responsible for multiple benefits:
Improve the immunity of the gut, as well as systemic immunity
Suppress excess immune response (one of the problems with Covid-19 infections).
Suppress chronic inflammation both in the gut wall and in the body generally
Promote integrity of the intestinal wall, and even the blood-brain barrier
Enhance the ability of immune cells to destroy harmful bacteria, as well as destroy damaged cells
Alter the genetic expression of cells by suppressing cancer cells and preventing cancer development
Prevent auto-immune conditions such as type 1 diabetes and rheumatoid arthritis.
Perhaps prevent allergic conditions in children such as asthma and hay fever.
Possibly even help with preventing premature labour.
So after all that high powered physiology, what is the take home message? Eat plenty of varied plant foods which are rich in a wide variety of fibre, to feed your gut micro-flora, and they will look after you. Be kind to them, and they will be kind to you.
Have a great week.
Dave Glass
Dr David Glass graduated from UCT in 1975. He spent the next 12 years working at a mission hospital in Lesotho, where much of his work involved health education and interventions to improve health, aside from the normal busy clinical work of an under-resourced mission hospital.
He returned to UCT in 1990 to specialise in obstetrics/gynaecology and then moved to the South Coast where he had the privilege of, amongst other things, ushering 7000 babies into the world. He no longer delivers babies but is still very clinically active in gynaecology.
An old passion, preventive health care, has now replaced the obstetrics side of his work. He is eager to share insights he has gathered over the years on how to prevent and reverse so many of the modern scourges of lifestyle – obesity, diabetes, ischaemic heart disease, high blood pressure, arthritis, common cancers, etc.
He is a family man, with a supportive wife, and two grown children, and four beautiful grandchildren. His hobbies include walking, cycling, vegetable gardening, bird-watching, travelling and writing. He is active in community health outreach and deeply involved in church activities. He enjoys teaching and sharing information.
