AUTHOR: Dr. Jason Bush

Your gut microbiome is an ecosystem and it will adapt to the resources that are available.  For example, providing your microbiome with prebiotics will stimulate the proliferation of bacterial species capable of fermenting this energy source.  In turn, these probiotic bacteria will shape the rest of the ecosystem by influencing the types of intermediate metabolites, pH level, and other species of resident bacteria.  Probiotic bacteria ultimately influence the physiology of the host as well.

What happens when you starve your microbiome by limiting or even eliminating prebiotics?  The probiotic bacteria that relied on prebiotics will decrease in number and the health benefits they provided will also diminish.  But starving the gut microbiome won’t lead to a digestive tract free of bacteria.  Instead, the bacteria that survive will begin to rely on a new source of food – produced in and supplied by the cells lining your colon.  In other words, your body will be making food for your microbiome.

Specialized cells lining the digestive tract secrete mucins, which are the large water-loving molecules found in mucus, a protective substance lining much of the gut.  While mucins serve to protect the digestive tract, their structure also makes them a source of food for bacteria living in the gut.  This is because mucins contain many short carbohydrate branches that can be cut off and fermented like other prebiotic oligosaccharides.  In this way, the bacteria of the microbiome can continue to grow when dietary prebiotic sources are limited.  Furthermore, certain beneficial bacteria, such as Akkermansia muciniphilia, can survive solely on mucin as an energy source.

This sounds reassuring, except that it requires a constant supply of mucin production and a gut microbiome that, for lack of a better term, isn’t too ‘hungry’.  If mucin production drops or bacterial degradation of mucus increases, the mucus barrier can be depleted and the epithelial layer of the gut exposed to potential damage.  This can lead to increased inflammation, leaky gut, or even sepsis.

Less serious but also upsetting is the fact that fermentation of mucins produces higher levels of Sulphur-containing byproducts than when plant-based prebiotics are fermented.  Sulphur byproducts tend to have unpleasant aromas and are responsible for the smell of rotting eggs.  So, relying on mucins to feed your microbiome can lead to higher levels of fecal odor and smelly gas.

Mucin degrading bacteria are not all bad but it is important to make sure that they do not dominate your microbial ecosystem.  Keeping your gut microbiome balanced and healthy by consuming prebiotics will help you get the most benefits while avoiding some serious health risks and – potential embarrassment – that goes along with feeding your gut microbiome too much mucin.