In what way are mushrooms an important source of food and do they have a relevance beyond simply interesting culinary additions to our diet. My interest here is whether mushrooms are a useful food source in survival situations or when humans live from the land.
Another way of asking this question is; did ancestral groups of hunter/gathers bother with mushrooms as an important source of food.
It is particularly relevant this season as it has obviously been a good year for some mushrooms – not so much for open grassland types, but particularly those that grow underneath trees or in woodland. I wonder if there is a link here since there is a mycorrhizal (symbiotic) association between specific fungi and tree species and this has been an obvious mast year’ for trees such as Beech, Hawthorn and particularly noticeably Oaks which causes them to produce an over-abundance of tree nuts. This is a periodic cycle that we do not fully understand but is probably due to climate and weather.
In the British Isles the collection of fungi - particularly fungi that produce fruiting bodies that we call mushrooms - does not seem to have a traditional of collection for food associated with it. Instead the British have maintained a ‘healthy’ suspicion of fungi with more of a suggestion of mysticism and a connection with ‘dark arts’, bolstered by the obvious hallucinatory effects of those fungi that were coined ‘magic mushrooms’ in the 1960’s, but whose psychoactive effects were known in human prehistory at least as far back as the Neolithic and therefore I would think much further back into human prehistory.
I have a feeling that this wary relationship with mushrooms emanates from the fact that we live in a temperate, maritime climate and therefore we have a huge range of fungi available to us – about 4000 different types – and therefore the chance to pick the wrong kind is a major threat given the number of mushrooms that are visually very similar to each other, coupled with some very lethal toxic defences that fungi developed to protect their soft-bodied mushrooms from predation.
Therefore, in terms of survival or living off the land, how do mushrooms as food fit in?
It has become of late, more of a popular pastime and some of our more edible species such as Chanterelle, Morel, Earth Ball etc have appeared on the plates of diners in expensive restaurants and I myself have tackled a sizeable steak with an equally large earthball at one restaurant that filled me up for a week!
The mushroom that most of us would recognise is actually the fruiting body of some species of fungi and all fungi are members of a specific Fungi kingdom that are separate from the animal and plant kingdoms and include other members such as the moulds and yeasts.
It is an ‘eukaryotic’ organism - don’t worry too much about this term since all multi-cellular organisms are eukaryotic, but fungi differs from plants and bacteria in that their cell walls contain something call chitin – which is a derivative of glucose – rather than cellulose which is found in plants. This element makes fungi – which is on little importance in this article - more closely related to animals than to plants since chitin also forms the exoskeleton of such animals as crabs, lobsters, shrimps and insects.
I could get very pedantic at this point and explain at length the importance that other members of the fungi have playing in human early food processing (the original processed food). For instance fermentation with yeast/bacteria was a common early process that can be found in beer, wine and bread production.
However, let us try and keep on the straight and narrow and concentrate on mushrooms. Mushrooms are soft fruiting bodies and it should not be a surprise to know that the most common constituent of the mushroom is water, making up 85 – 95% of the mushroom. Given this, it is not surprising either that therefore fresh mushrooms contain very little calorific content.
Now I am not alone in believing that Wilbur Atwater’s ‘calorie’ is not entirely foolproof in describing the energy content of food, but let us just say that is provides the ‘potential energy’ content of food and along with the kilojoule, they have continued in popular usage. However what they do not describe is how that potential energy reacts with the human digestive system, but that is another article.
Let us list the seven groups of nutrients that are important to human health because we have already explained that mushrooms are low in two of them, carbohydrates and fats. The other five elements are: Proteins, Vitamins, Minerals, Dietary Fibre and of course Water.
Mushrooms do contain protein and although not as much protein as meat (perhaps about 10% per kg the amount of protein as to the same weight of meat), the protein comes in the form of what are called ‘conditional amino acids’ such as glutamic, aspartic acids and arginine that are important for the body in times of biological stress.
A word of warning however, since most studies are done on dried mushrooms and therefore might over over-estimates the amount of protein in fresh mushrooms by as much 200%.
The biggest nutritional importance of mushrooms is as a source of vitamin B particularly B2 (Riboflavin) - which plays a key role in the metabolism of fats, ketones, carbohydrates and proteins within the human body – and vitamin B3 (niacin) which is involved in the catabolism of fat, protein and carbohydrate as well as the anabolism of fatty acids and cholesterol synthesis.
A deficiency in niacin is most notable in high-energy organs such as the brain and gut and in mild cases causes decreased tolerance of cold and in extreme cases leads to a condition called Pellagra, the symptoms of which are described as the ‘four D’s”: diarrhea, dermantitis, dementia and death (which tends to be fatal).
Riboflavin deficiency used to be called Pellagra sin pellagra (pellagra without pellagra) since the symptoms were very similar to niacin deficiency, however it is now called Ariboflavinosis and results in growth failure, weakness, ataxia, and inability to stand before becoming comatose, and eventually death.
Mushrooms are also good sources of essential minerals such as potassium, containing twice the amount of potassium per weight as bananas. Potassium is an abundant mineral in the human body with only calcium (the constituent of bones) and phosphorus more abundant and its role lies in brain and nerve function and cellular health – if I say anymore we would get into the role of the NA+/K+-ATPase pump which exports sodium out of cells and imports potassium.
Deficiency in potassium or low blood potassium levels – Hypokalaemia – due to starvation is rare in humans since potassium is present in sufficient quantities in most fruit, vegetable, meat and fish. In its mild state hypokalaemia presents almost no outwardly discernable symptoms at all, however moderate or severe hypokalaemia can be caused due to heavy fluid loss through diarrhea or excessive sweating, which is relevant to survival situations. Vomiting can also cause mild potassium deficiency, but since not much potassium is lost through vomit, it would be unusual to exhibit moderate or severe hypokalaemia by this means.
Another mineral that mushrooms do contain is Selenium. Like potassium, this is important for cellular function and is actually toxic in large amounts, which is why some plants harness it as toxic defence.
Selenium as a trace mineral in the human body, but it is essential for human health since it role is as a component of the antioxidant enzymes glutathione peroxidase and thioredoxin reductase that reduce oxidative damage particularly to DNA which is thought to be involved in the development of human conditions such as cancers, Parkinson's disease and Alzheimer's disease etc.
Selenium deficiency is a chronic condition that is rare in healthy humans and instead tends to be present in human population from areas of the world where there are low concentrations of selenium in the soil, such as part of China where, in combination with Coxsackievirus infection can lead to Keshan disease, which is potentially a fatal conjestive cardiomyopathic condition i.e. a heart condition. It would be unlikely to affect otherwise health people in survival situation over comparatively short periods of time, although to the symptoms of Keshan disease - weakening of the heart and degeneration and necrosis of cartilage tissue – would be significant factors in survival situations.
Copper is another nutrient that is present in useful quantities in mushrooms. It is an essential trace element in the human diet that is necessary for a whole range of biological processes from the proper maintenance of bone, connective tissue, brain, heart, and other body organs, to the formation of red blood cells, the absorption and utilization of iron, the metabolism of cholesterol and glucose, and the synthesis and release of life sustaining proteins and enzymes. These enzymes in turn produce cellular energy and regulate nerve transmission, blood clotting, and oxygen transport.
Given copper’s association with iron transport within the body, it is not surprising that copper deficiency produces anaemia-like symptoms. In fact the body carries out complex ‘homeostatic’ processes to ensure a ‘sufficient and constant’ supply of copper within the body since not only does a deficiency of copper have negative effects, so does excess levels of copper which are toxic.
Ironically it has been suggested that western diets are deficient in copper and therefore this condition is under-diagnosed and therefore more common than suspected. This mild copper deficiency can affect human health in subtle way such as lowered resistance to infection, general fatigue, impaired neurological function and an elevated risk of coronary heart disease.
However copper deficiency is again a chronic deficiency rather than an acute condition that would not have significant implications on someone within a survival situation over short periods of time.
In part two I will discuss medicinal qualities and the evidence for fungi use into prehistory and amongst hunter/gather groups.