Mucous: Gooey, slimy . . . and necessary

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You probably don’t think too often about the mucous lining of your gastrointestinal tract, this mix of proteins and polysaccharides that provides a barrier between the gastrointestinal lining and gastrointestinal contents.

Without it, however, and you would not survive for long. Inflammation, infection, and dysbiosis would proceed unchecked and you would promptly die. Mice bred to not produce mucous die within weeks. The gastrointestinal lining is therefore a vigorous producer of mucous that not only provides protection against pathogens, potential toxins, and foods as they are digested, but also otherwise highly toxic hydrochloric acid produced by the stomach and bile acids produced by the liver, either of which, without the protection afforded by mucous, would promptly destroy the intestinal lining. In short, we are all less than one millimeter of mucous away from intestinal destruction and self-digestion. You’ve likely seen some form of mucous: gooey, slimy, tough to rinse off your hands, as the mucins contained form complex polymers, long chains that are tough enough to be resistant to acid, bile, and most bacteria. Mucous is therefore a crucial factor in gastrointestinal health.

Remarkably, the science exploring intestinal mucous is a relatively recent development that parallels exploration of the human microbiome. It is now clear that bacteria normally do not directly contact the intestinal lining, as the mucous layer provides a barrier, a crucial and necessary barrier. But the mucous lining is also vulnerable to anything that disrupts its structure and affects its production.

The mucous lining is therefore something we do not want to disrupt. One illustration of the importance of the mucous layer comes from observing the effects of emulsifying ingredients added to processed foods, additives such as polysorbate 80 and hydroxymethcylcellulose frequently found in synthetic coffee creamers, ice cream, hot cocoa mixes and many other products. The emulsifying effect acts like detergent, disrupting and dispersing mucous and disabling its protective function. Among the consequences is an unhealthy shift in bowel flora composition and intestinal inflammation, effects that are nearly immediate. Such changes also amplify the toxic potential of factors such as non-steroidal anti-inflammatory drugs commonly used to “treat” arthritis pain or headaches. Conditions such as ulcerative colitis are associated with an abnormally permeable and ineffective mucous lining. Some pathogenic bacteria, such as Entamoeba histolytica that causes amebic dysentery, exert their effects by first disrupting or penetrating the mucous lining.

This brings us once again to the unique bowel flora species, Akkermansia muciniphila, the only member of the Verrucomicrobia phylum commonly found in the human gastrointestinal tract, primarily the colon. I have previously discussed how, when deprived of prebiotic fibers, Akkermansia has the unique capacity to digest human mucous as its nutritional source, a characteristic it shares with some of the species of Bacteroides. The lack of prebiotic fibers is also known to dramatically increase the numbers of Akkermansia, likely because, in the absence of prebiotic fibers, most other bacterial species either become quiescent or die because they do not have the capacity to thrive on mucous alone. And Akkermansia does so vigorously, reducing the mucous lining to a fraction of its normal thickness. Anytime you therefore fail to take in plentiful prebiotic fibers, you allow the proliferation of Akkermansia, as well as some mucous-degrading Bacteroides, at the expense of other bacterial species, while encouraging digestion of the mucous lining. It is also now clear that repeated or prolonged degradation of the mucous lining, whether by polysorbate 80, various drugs, pathogens like Entamoeba, or normally friendly Akkermansia, invites trouble in the form of intestinal inflammation, dysbiosis, and inflammation in other parts of the body. While many of the beneficial effects of bowel flora are mediated via butyrate, these effects have nothing to do with butyrate.

Part of your mucous preserving program is therefore to be mindful of prebiotic fiber intake. Deprive yourself of prebiotic fibers, whether you call it a “ketogenic diet,” “carnivorous diet,” or an ultra-low-carb diet, and you risk sacrificing the mucous lining of your gastrointestinal tract. Include around 20 grams per day of prebiotic fibers and you have taken the first step in cultivating a healthy and protective mucous lining.

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