In the first installment of FungiFacts, we looked at facts about the fungal kingdom in the outside world — ecology, history, civilization. In this second installment we go deeper: the connection between fungi and the human body, which turns out to be far closer and older than most people imagine.
FungiFacts — Installment #2: Fungi and Your Body
#1 — Your body hosts dozens of fungal genera.
The human mycobiome — the collection of fungi living in and on the body — includes dozens of different fungal genera in healthy individuals. The skin, mouth, gut, lungs, and genitals each host specific fungal communities. Candida, Malassezia, Aspergillus, and Saccharomyces are normal resident genera. Most are entirely benign or beneficial — only when the balance is disturbed (by antibiotics, immunosuppression, or chronic stress) can they cause problems.
#2 — The antibiotics we take are produced by fungi — to kill the bacteria that compete with them.
Penicillin, cephalosporin, griseofulvin, and cyclosporine are compounds fungi evolved as chemical weapons in their ceaseless war with bacteria over the same resources. When your doctor prescribes amoxicillin, in a sense they are dispensing a fungus's arsenal. Fungi have been waging that chemical war for hundreds of millions of years — we simply learned to recruit their weapons.
#3 — Fungal chitin and the exoskeleton of insects are chemically identical.
The cell wall of fungi is made of chitin — exactly the same polysaccharide that forms the shells of crabs, lobsters, insects, and spiders. Fungi are more closely related to animals than to plants — and chitin is one of the molecular clues. Interestingly, this carries practical implications: chitin inhibitors (compounds that interfere with its synthesis) are a promising target for antifungals, because humans do not produce chitin and a compound that blocks it should not be toxic to us.
#4 — Fungal beta-glucans activate the immune system through the very receptors that recognize dangerous pathogens.
The immune system carries specialized receptors (Dectin-1, TLR-2) that recognize beta-glucans — the structural signature of fungal cell walls. It reads them as a sign of fungal presence and mounts a defensive response. When you take a medicinal-mushroom extract rich in beta-glucans, you are essentially handing the immune system a low-risk drill: it rehearses its response to fungal structures without any real infection. It is a way of keeping the immune system “in shape.”
#5 — Your body produces endocannabinoids — and fungi produce compounds that modulate the same system.
The human endocannabinoid system — the network of CB1 and CB2 receptors that regulates pain, sleep, appetite, and mood — has fungal analogs. Some compounds from Reishi (Ganoderma lucidum) interact with endocannabinoid-system receptors, which may explain part of its anxiolytic and sleep-supporting effects. The link between fungal pharmacology and the endocannabinoid system is an active area of research.
#6 — Psilocybin — the compound in psilocybin mushrooms — is structurally similar to serotonin.
Psilocybin is a prodrug the body converts into psilocin, which in turn binds serotonin receptors (5-HT2A) in the brain. The structural resemblance between psilocin and serotonin is so close that the receptor mistakes one for the other. In current clinical research (Johns Hopkins, NYU, Imperial College London), psilocybin is showing remarkable results for treatment-resistant depression, PTSD, and addiction — not because it “works magic,” but because it activates the serotonergic system with unusual intensity, favoring neuroplasticity and the reconnection of neural networks that become “stuck” in chronic depression.
#7 — Ergotamine — derived from the rye fungus — inspired the synthesis of LSD.
Claviceps purpurea is the ergot fungus — rye ergot. In the Middle Ages, mass poisonings from rye bread contaminated with this fungus produced collective episodes of seizures, hallucinations, and gangrene known as “St. Anthony's Fire.” In 1943, the Swiss chemist Albert Hofmann, then working with ergot alkaloids in search of circulatory treatments, accidentally synthesized LSD-25 and, absorbing traces through his skin, experienced the substance's first effects. The rye fungus — an agent of medieval terror — became the starting point of twentieth-century psychedelia.
#8 — Fungi produce vitamin D₂ when exposed to UV light — just as your skin does.
The ergosterol in fungal cell walls converts into vitamin D₂ (ergocalciferol) on exposure to ultraviolet radiation — exactly the mechanism by which your skin makes vitamin D₃ in the sun. A portobello mushroom left in the sun for fifteen minutes can hold 400 IU of vitamin D₂ — enough to cover the recommended daily intake. That makes mushrooms — Shiitake and Maitake especially — one of the few natural vegetarian sources of vitamin D.
#9 — The Nerve Growth Factor (NGF) that Lion's Mane stimulates is also involved in chronic pain.
NGF does not only regulate neuronal growth and survival — it is also implicated in the sensitization of chronic pain. This explains an apparent paradox: in pain research, anti-NGF antibodies are being studied for chronic pain (blocking NGF reduces pain), while in neurology, compounds that raise NGF are being studied to treat degeneration. Lion's Mane, by stimulating endogenous NGF in a localized, moderate way, could act in a therapeutic range between the two extremes — enough to support neuroplasticity without tipping into painful sensitization. Research on this point is still preliminary.
#10 — Fungi and humans share an ancestor — which explains why so many fungal compounds are biocompatible with our systems.
The common ancestor of fungi and animals (humans included) lived roughly one billion years ago. We share fundamental metabolic pathways — among them the citric acid cycle and parts of the mitochondrial respiratory chain. This evolutionary closeness explains why so many fungal compounds interact with human physiology in pharmacologically meaningful ways: we are not as different as we appear. We are, in a sense, distant cousins of the mushroom we take in the morning.
The next installment of FungiFacts will explore the relationship between fungi and the future: mycelium materials, mycoremediation, mycoprotein, and what lies ahead in psilocybin research.
→ FungiFacts #1 — 15 facts that will reconfigure your perspective
→ The active biocomponents of our fungi
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