When people commonly say the word “mushroom”, they are referring to the fruiting body of the basidiomycete organism, otherwise known as a fungus, or plural, fungi. This organism also has two other parts, the mycelium and the spore. Frequently however the word “mushroom” is used to refer to the entire organism.

This misconception is abused by marketers selling cheap mushroom powders - most US producers of powders sell ground up mycelium in substrate (usually starch), which due to poor regulation in the US supplement industry is allowed to be labelled as mushrooms. The starch has no medicinal value and is considered a filler.

The majority of the medicinal value is concentrated in the fruiting body, the true mushroom, not the mycelium. So be careful - when you think you are buying true mushrooms, in most likelihood you are actually buying a bunch of starch and some mycelium. It’s not the same.

It’s no surprise this happens because there is much confusion between fungus, mushrooms, and mycelium. So let's look at the basic fungus lifecycle.

Fungus is the organism that many of us refer to when we talk about mushrooms. A fungus has a life cycle, from spore, to mycelium, to fruiting body (or mushroom). Whenever we refer to the species and not the specific body part, we try to use fungus or fungi, rather than the commonly used "mushroom" which is technically incorrect.

Spore. The reproductive elements of the fungus, you can think of these as the seed. These are tiny particles that are so hardy they can travel through space and last survive hundreds of years.

Mycelium is a stage in the life cycle of the mushroom that is largely invisible to humans as it is below ground. It can be considered the fungal “body”. The mycelium secretes enzymes to digest organic compounds that surround it in the substrate that it grows in. In doing so it offers a vital ecosystem function, and gathers nutrients for the fungus.

Mushroom is the reproductive stage in the life cycle of the mushroom that is visible to humans. It can be considered the fungal “fruiting body”. In the mushroom is where the nutrients gathered by the mycelium are accumulated, and where spores are produced. It’s in the mushroom that complex natural compounds are formed that can contribute to a wide variety of health benefits in humans.

So hopefully now you can see why using mycelium and mushrooms interchangeably is an error - they are both part of a fungus, but their purpose and structure are far different. Growing true fruiting body mushrooms is expensive which is why so few people do it. Most mushroom supplements in the US are myceliated grains, which even well known and respected suppliers in the US quietly use because it is far more profitable. Not only are you primarily consuming starch filler because the mycelium can’t be separated from the grain, the mycelium are of far less medicinal value than the mushroom!