Ergothioneine, a mushroom-rich antioxidant, can cross the blood–brain barrier and has a long body half-life of about 1 month. Mushrooms contain 0.1–7.0 mg/g ergothioneine, and Parkinson’s patients showed 45% lower serum levels in one human study. Preclinical models link ergothioneine to lower α-synuclein aggregation, stronger mitochondrial function, reduced oxidative stress, and better motor outcomes, making this one of the strongest mushroom brain-health stories.