This study shows how adding olive mill waste to mushroom growing substrate can increase beneficial compounds in mushrooms while reducing harmful toxins. Researchers grew two types of edible mushrooms (lion’s mane and king oyster) on substrate containing different amounts of olive mill waste and used advanced chemical analysis to identify how the waste affected the mushrooms’ medicinal compounds. Adding olive mill waste increased healthy compounds like hericenones and erinacerins while decreasing toxic enniatin compounds, potentially creating safer and more nutritious mushrooms for consumers.