The term superfood is banned by the European Food Safety Authority, and in order to label a food that way, the industry would have to show human intervention studies to prove the food did as they claimed.
So we cannot call mushrooms a superfood in labels, but we can still promote the idea of the mushroom as a superfood.
The science does back up the claim for mushrooms in many areas, being beneficial as an addition to any diet. As ever, a balanced diet is the way to go, and one that contains mushrooms is for sure even more balanced than one that does not!