There’s a peculiar situation that is believed to develop when bowel flora are deprived of prebiotic fibers: They consume the mucous lining of the intestinal tract. The issues are a bit complex, so be sure to have your first cup of coffee before proceeding.
In other words, bacteria that reside in the intestines need to “eat.” They therefore depend on fibers, i.e., polysaccharides, that you ingest. Humans lack the digestive enzymes to break down the fibers consumed by bacteria, so-called prebiotic fibers. Prebiotic fibers therefore make their way down to the colon where bacteria who have the appropriate enzymes to digest these fibers metabolize them to the fatty acids, acetate, propionate, and butyrate. Butyrate in particular provides substantial health advantages to the human host, mediating improvements in insulin responsiveness, blood sugar, reduced triglycerides, reduced LDL particle number, reduced blood pressure, healthier intestinal lining, better sleep, less anxiety, better mood.
But consume a diet with too little prebiotic fibers and something odd happens: Microorganisms, like all other living creatures, have evolved to survive even when conditions are imperfect or undesirable. When there are no prebiotic fibers available, they turn to the mucopolysaccharides of the intestines, i.e., intestinal mucous. This degrades and thins the mucous barrier of the intestines, making your intestines and your body more susceptible to disease. The mucous lining is critical to intestinal and overall health, as without it, colitis, widespread inflammation, autoimmune diseases, colon cancer, and eventually death occurs.
The foundational species (meaning it is a crucial inhabitant of the human gut whose presence supports the growth of other beneficial microbes), Akkermansia muciniphila, that, as its name suggests (mucin + phila = mucous-loving) consumes the mucous of the intestines and is normally among the most beneficial of bacterial species, explodes in number when prebiotic fibers are not present, a situation that is associated with adverse effects including cancers. Several other bacterial species have been associated with this effect, also, when deprived of prebiotic fiber including several species within Bacterioides that, when prebiotic fibers are available, are anti-inflammatory and strengthen the intestinal barrier; when fiber-derived, they degrade and thin the mucous lining, promote inflammation, and weaken the intestinal barrier. In other words, deprivation of prebiotic fibers converts friend into foe.
Failure to consume prebiotic fibers therefore disrupts the mucous lining, the biofilm, a situation that, if sustained repeatedly, invites inflammation, penetration of the intestinal lining by bacteria, changes in bowel flora composition, and can thereby lead to bowel inflammation, triggering of autoimmune diseases, and colon cancer.
What practical lessons can we take from these observations? We can reasonably surmise that:
- This is yet another reason to be sure that you take in foods with prebiotic fibers regularly. It means including root vegetables, legumes, inulin, raw white potatoes and other sources every day. It doesn’t take much: a small raw potato chopped into a salad, a teaspoon of inulin added to coffee or yogurt, a 1/4 to 1/2 cup serving of chickpeas or white beans, etc. Maximal benefit occurs with a prebiotic fiber intake of 20 grams per day.
- Diets that avoid prebiotic fiber sources, such as ketogenic or carnivorous diets, invite trouble long-term. Brief periods of such diets are harmless, but followed chronically can lead to a variety of health problems. This is not my speculation but based on studies documenting adverse health effects that include kidney stones, osteopenia/osteoporosis, stunted growth in children, metabolic deterioration despite the upfront early benefits, narrowing of species diversity in bowel flora and proliferation of Akkermansia that we now know means that some species will resort to digesting the intestinal mucous lining.
- Avoid other factors that degrade the mucous lining. Beyond the above, we also avoid such things as polysorbate 80, hydroxymethcylcellulose, and N-acetyl cysteine that emulsify the mucous lining. (We use N-acetyl cysteine for brief periods to purposefully disrupt the mucous lining during efforts to eradicate H. pylori, SIBO, and SIFO, but never chronically, contrary to programs that recommend this agent for its purported brain benefits.)
The new lessons being learned about bowel flora can be incredibly empowering, such as the oxytocin-boost we obtain from our L. reuteri yogurt, effects that are unprecedented and obtained on your own in the comfort of your home without the interference of the doctor or healthcare system. But new lessons on what we should not do are also emerging. Failing to obtain prebiotic fibers is a new and powerful lesson that we all need to pay attention to.