The nutritional value of fungi or mushroom is very high. Fungi, like all vegetables, is primarily a carbohydrate. It is 50% carbohydrate, 37% protein and 13% fat. It is also extremely low in calories, saturated fat, cholesterol and sodium.
However it is also a good source of Dietary Fibre, Protein, Vitamin C, Folate, Iron, Zinc and Manganese, and a very good source of Vitamin D, Thiamin, Riboflavin, Niacin, Vitamin B6, Pantothenic Acid, Phosphorus, Potassium, Copper and Selenium.
They are therefore deemed as being very diet friendly and a healthy addition to a balanced diet. One cup of fungi is equal to 15 calories. It can be a great way of bulking out a healthy meal to make you more full.
Although fungi is classified as a vegetable, fungi is technically a classification in itself. The main difference between fungi and vegetables or plants is that it contains an indigestible carbohydrate called Chitin which can also be found in prawn and crab shells.
Fungi increases its vitamin D content when exposed to light, much like the human skin and is therefore a unique vegetable as it is the only vegetable from which we can get vitamin D when usually our only natural sources of vitamin D is from the sun. A lack of vitamin D can lead to bone weakness and deformity which can cause rickets in children and osteomalacia in adults. Pregnant women especially are encouraged to take vitamin D supplements to ensure there is a good foetal store in early foetal development.
With fungi being high in B vitamins, they can also kick start your metabolism and immune system.
However, there are many species of fungi that one must avoid. Psilocybin mushrooms are commonly known as 'shrooms' or 'magic mushrooms' and can cause hallucinations. You can see this type of fungi in the picture below.
There are also countless mushrooms that are poisonous or that can even cause death. It is even said that the Emperor Claudius in AD 54 died from eating a poisonous mushroom. So always check the species of the fungi before eating it, especially if foraging them yourself.