This is a great question, and one that has intrigued us here at The Fungi Folks for some time. We could approach this question on several different levels – what bioactive compounds do they possess, how do they interact with our physiology, how does this relate to how they live in their own natural environment… The truth is that (as far as we’re aware) there isn’t a clear answer. And this is the case for a lot of questions that the Fungi pose – they are mysterious, and they have been largely ignored by Western science for generations, and so our understanding is often lacking. How do we begin to pick apart the complexities of this vastly expansive, entangled, and intricate Kingdom of Life. We have a long way to go. However! We shall give this question our best shot…
Bioactive Compounds
Firstly, we are aware of many of the bioactive compounds present in mushrooms that carry medicinal value, and we can give some examples here.
One of the main bioactive compounds found in mushrooms are beta-glucans. These are a type of polysaccharide (long chains of sugar molecules) that are found in other foods too, but Fungal polysaccharides have specific benefits.
These specific Fungal beta-glucans are 1-3,1-6 beta-glucans, and have several health benefits. They are found in the Fungal cell wall and are responsible for much of the immune function of medicinal mushrooms (1). They interact with receptors in the small intestine that stimulate an immune modulatory response. These beta-glucans also have prebiotic functions in the gut which has knock-on effects on the brain and are also involved in blood sugar regulation.
Fungi are often referred to as natures master chemists, producing a fantastic array of compounds. Reishi are often touted for their triterpene content, Cordyceps for their nucleosides – adenosine and cordycepin, Shiitake for its AHCC polysaccharide, and Lion´s mane for its erinacines and hericenones… The list goes on and on, and we are only beginning to discover the extent of these bioactive compounds in functional mushrooms.
Shared Evolution
However, the previous paragraph perhaps doesn´t really answer the question!
The reasons why mushrooms are medicinal are less clear but allow us to speculate! One possible approach to looking at this question is to look at the evolutionary history of Fungi.
As we know through the study of phylogeny and evolution – life evolved from single celled organisms somewhere around 4.1 billion years ago. From this point the innumerable branches of life have bloomed and split off from one another creating the diversity that we see today. Fungi are often miscategorised as plants, but of course they are their own kingdom of life, with whom we as humans have a shared evolution. We are more closely related to fungi than we are to plants, sharing a more recent common ancestor. Humans and Fungi belong to a clade known as the Opisthokontha. Therefore it stands to reason that there must be a certain degree of biochemical similarity.
One obvious example of this is that we respire in the same way as fungi – inspiring oxygen and releasing CO2. Perhaps this is why many fungal compounds have such an interesting effect on our human physiology.
Interestingly, recent advances in genetic and biochemical analysis have shown that some of the medicinal compounds found in plants actually come from endophytic fungi living inside the plants! One example of this is the chemotherapy drug Taxol – a compound identified in yew trees that is produced by a fungal endophyte (2). It is likely that this is not an isolated example and continued study of fungal endophytes may reveal more medicinally valuable findings.
The Life of Mycelium
Another way that we can look at this question is to look at the ways fungi live in their natural environment.
A mushroom is only the reproductive organ of a fungus – and many fungi do not produce mushrooms at all! The main way that fungi inhabit their environment is as mycelium.
Mycelium is a branching structure of cells called hyphae whose network radiates out through a particular niche – whether that be the soil, a tree, inside a plant, etc. Mycelium does not possess skin, or mucous membranes like us to protect itself from pathogenic microorganisms – it is completely open to attack!
However, as the masterful chemists that they are the fungi have a range of compounds known as secondary metabolites that they exude that have antimicrobial properties to protect themselves from other microorganisms. This could be why fungi have many antimicrobial properties in humans as well, and have been used for the treatment of infections.
Conclusion
These are just a few possible reasons that Fungi are medicinally active, but again the truth is that we don´t really know. Our hope is that the recent surge in interest in Fungi and Mycology will encourage a broadened research effort, both within scientific institutions and in the community of citizen scientists and Fungal enthusiasts, and that over time we will come to better understand and honour these incredible organisms.