Merlin Sheldrake’s “Entangled Life” is one of the best books I have read in recent years. He recently appeared on the ZOE podcast (together with Professor Tim Spector) to discuss fungi and why their unique composition means they offer significant benefits to our health, with certain species being used to treat conditions ranging from depression to cancer.
Some of my notes are below the embedded video (any mistakes are my own).
What are fungi versus mushrooms?
Merlin Sheldrake (MS): Fungi are a kingdom of life. That is as broad a category as animals or plants. Mushrooms are the reproductive structures of a proportionately small group of fungi. Mushrooms are the places where fungi produce spores, to help disperse themselves over potentially large distances. So when we think about mushrooms, we are just thinking about a small part of the overall life of a fungus, which is usually in the form of a network of branching, fusing cells called a mycelial network.
The most important difference between fungi and plants is that plants on the whole photosynthesize, so they produce energy from the light coming from the sun and from CO2 in the air. Fungi don’t photosynthesize. Like animals, they have to find food in the world and put it inside them. They can’t make their own energy containing carbon compounds like plants do. Fungi grow into mycelial networks which allow them to bury and insinuate themselves within their food source. Because they are highly branched, they can make contact with as much of their surroundings as possible, which they then digest by releasing enzymes and other digestive compounds to break down their surroundings and absorb those nutrients into their networks.
Fungi are metabolical wizards, they can produce all sorts of fascinating chemicals that allow them to interact with the world in strange and remarkable ways. This allows them to play important roles in the biosphere, for example, by decomposing wood. But they aren’t just powerful decomposers, they also play important roles in making life on land possible. All plants, for example, depend on symbiotic fungi that live in or on them to survive. Plants would not have made it out of the water and onto the land about 500 million years ago were it not for the fungi they formed relationships with. So fungi are symbionts, decomposers and through all this activity they play a part in regulating the composition of the atmosphere when they support plant life, they help pull down CO2 into stable forms in the soil. They also hold soil together by forming a sticky, living seam – if you take away the fungi, the soil would wash away.
On the connection between fungi, plants and gut health:
MS: Fungi form relationships with plants, perhaps in the most important way by living in and around plant roots, extending their exploratory webs into the soil and foraging for nutrients such as nitrogen or phosphorous, which they are able to find more easily than plants can. They transport these nutrients back to the roots and exchange it with plants for sugars and fats that plants have produced in photosynthesis. So they essentially have a trading relationship with plants. Together, they are able to extend their reach and do things that neither could do alone.
Researchers are still trying to better understand how fungi are able to behave as networks, how they are able to live in a changing world by sensing their environment (temperature, chemicals, acidity etc.) and how they are they able to integrate all of these different sensory data streams and decide on the right course of action. Scientists are now are looking inside these networks using microscopes and watching flow patterns. One of these fungi may be sprawled over tens of meters, engaging with millions of plant root tips, managing an uncountable trading network with plants and constantly remodeling itself from day to day and season to season.
Tim Spector (TS): There are some obvious links between soil health and gut health. The ratio of fungi to microbes in soil is actually a really good indicator of the health of the soil. In areas where there are less fungi networks, that soil isn’t as nutritious or it is harder to grow things. That is just like humans who have lost diversity of their microbes. We know there are fungi in the human gut and we estimate that about ~8% of our microbes are fungal but that is a bit of a guess because they are hard to sequence genetically. We used to think about them as harmful within our gut, but there is no real evidence of that view and a lot of evidence that they play a protective, symbiotic role working with bacteria to help maximize nutrition, reduce inflammation and keep the gut wall structurally sound.
On the human impact on fungi:
MS: If we cut down a forest that was home to a whole load of fungal species that depended on those plants to live (and to live with), you have destroyed the habitat for a whole load of fungi that can live there. But you have also created a habitat for a whole load of different type of fungi. For example, you might have fungi that thrive on rotting wood, so if a forest is killed by a disease and you have a lot of dying wood around, that will create a habitat for a different group of fungi. When we do large scale, industrialized agriculture, we are often damaging fungal communities. You get lower fungal diversity and less healthy, less active groups of fungi in those places. Plants have evolved for hundreds of millions of years to do what they do in association with fungi. Modern-bred varieties of plants and crops might not be as good at forming relationships with their companion fungi as a variety that has been grown by humans for a long time before fertilizers started to be applied.
TS: The analogy can be made that if you feed any animal massively and it balloons up in size, it may have more height and weight but it is going to lack some nutrients, defense chemicals, complexity etc. and its interaction with the world is going to be different, because all you are focusing on is the size of that animal or plant. They are lazy and don’t have to do much hard work because the fertilizer is this massive growth hormone that pushes them up.
On mushrooms and mental health:
TS: Mushrooms have been used medically for thousands of years. Some mushrooms produce a substance called psilocybin, which is a very powerful neurochemical in the brain and is closely linked to the drug LSD. LSD was around in the 1960s and there was a brief time when it was thought to be useful therapeutically. But for the last 30-40 years, it has been seen as a bad drug. It got labeled the same way as heroin, cocaine etc. It turns out that was more of blanket reaction to all drugs than to what might actually be a very useful tool in psychiatry.
There have been no new drugs in psychiatry in almost 30 years but they have now started proper clinical trials with doses of psilocybin, which is easier to dose than LSD and has shown remarkable benefits for people with severe depression that have been resistant to medication as well as some cases of anxiety, psychosis etc. There are some encouraging signs that it can reset the brain through these chemicals changing some of the neural pathways inside the brain in positive ways. There are companies now looking at biosimilar compounds that fungi are producing as potential medications for mental health.
On the use of mushrooms in other areas of medicine:
TS: There is quite a lot of going on in cancer. Not as a main treatment but there are some test tube studies show that when you dry certain mushrooms and put them in test tube plates you can get immune benefits and anti-cancer benefits. But the real proof is in human studies and there aren’t many of those. There have been some observational studies but not trials. There was a Cochrane Review looking at small studies of reishi mushrooms that showed if it was given in addition to chemotherapy you get improvements in those cancer outcomes. This is where the field is going, there are hundreds of chemicals in these mushrooms and fungi that are having some benefits on our immune system that are maybe helping us respond better to these drugs. This is similar to what we see in the human gut as well.
MS: Fungal enthusiasm is also not equally distributed around the globe, more widespread in East Asian cultures than in the West. In Japan, there is a chemical from shitake mushrooms which is used very widely for treating cancer alongside more traditional cancer treatments as well as a compound from turkey tail which is used widely in quite conventional medical contexts. Part of the reason they are not so widely used in the West is because it is not totally clear how they are working, although it seems to be clear that they do work. Many of these medicinal fungi have been known about and used by traditional cultures for a really long time, including psychedelics. What is happening more in these modern scientific contexts is we are trying to understand more about how they work.
On why should we eat more mushrooms:
Tim: they have an amazing range of chemicals that give this umami taste, sort of mimicking meat in many ways. In many cases, you get even more taste if you dehydrate them and rehydrate them. There is a lot of water in mushroom so by cooking them, you get rid of a lot of the water and get more flavors that way. Mushrooms have huge amounts of protein, good amounts of fiber. They are also a source of selenium and Vitamin D. It is easier to get the nutrients from them if they are slightly cooked because they have this special layer called chitin, which is very hard to break down.
MS: Fungi haven’t been busily evolving for a billion years to give us Vitamin D. They need many of these molecules themselves to do a lot of the basic things they need to do. For example, when we use penicillin, which is a very famous fungal drug, the fungus is producing that antibiotic to defend itself from bacteria. When we use it, we are rehousing a fungal solution in our bodies. You can think of a lot of the nutritional content of mushrooms as something similar. There are a lot of things chemically that fungi can do for us that plants can’t because they are so chemically ingenious. They produce all these different compounds to do all these different things. A lot of the chemicals you get by eating a plant have originally been concentrated or made by a fungus. Much of the phosphorus that is in your body would have passed through a fungus on the way to a plant.
On the nutritional value of dried mushrooms:
TS: There are studies looking at the nutritional content of dried mushrooms, a lot done on shitake mushrooms in particular, as well as porcini which Italians often store dried. They are just as nutritious, healthy and some people think they are more tasty when they are rehydrated. Unlike grinding into a powder, however, you still want to keep some of the structure because there are studies showing that the cell walls themselves can have some benefits as well. But you should find a reputable supplier of dried mushrooms because you often can’t confirm visually that it is the species the package says it is. If you are trying to make a big difference to your health, the more mushrooms you get in your diet the better and try and vary the species as well. As with plants, diversity is key.