Slippery Elm and the Microbiome

Ever since reading The Human Superorganism by Rodney Dietert about a month ago, I have been obsessed with the role of the microbiome in human health. One of the things that has been mentioned frequently in my informal literature review is the role of the microbiome in creating an appropriate barrier between the external environment and the inside of the body. It is this barrier that prevents what is commonly known as leaky gut syndrome.

https://www.gutmicrobiotaforhealth.com/en/microbiota-plays-key-role-in-shaping-intestinal-barrier-structure-and-permeability/

This got me thinking about some traditional herbal medicines that have a history of being used to normalize the function of the large intestine.

When I first began my studies of herbal medicine around 1984, one of the peculiar substances that kept appearing on my radar was slippery elm (Ulmus rubra). It has a soothing effect in a wide range of respiratory and digestive tract problems. Interestingly, It is most well known for its effects on both the lung and large intestine, which are considered paired organs in traditional Chinese medicine. 

WebMD has a good evidence-based summary of its properties:

https://www.webmd.com/vitamins/ai/ingredientmono-978/slippery-elm

A quick search brought me to a study that showed slippery elm did indeed have a very significant beneficial in vitro effect on the composition of the microbiome:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6065514/

If this effect can be demonstrated in vivo, it would help explain something that has always been a mystery to me, which is how a very small amount of an herb with no significant pharmacological activity could be so powerful in its reported effects. Turns out it’s a food that is really liked by certain beneficial microbiota, which are known to secrete substances that repair the intestinal walls.