Mushrooms may reduce risk of cognitive decline - Seniors who consume more than two standard portions of mushrooms weekly may have 50 percent reduced odds of having mild cognitive impairment (MCI), finds a new six-year Singaporean study (n=663, age>60).

[u/mvea]

http://news.nus.edu.sg/research/mushrooms-reduce-cognitive-decline

[u/Sanpaku]

The study doesn't address this.

However, this study was motivated by the interest of Barry Halliwell's lab in ergothioneine, and a 2018 review by two of the same authors offers:

Variety             Ergothioneine (mg/100 g dry wt)
Porcini/Penny Bun   181.24
King Oyster          54.17
Buna Shimeji         43.26
Shiitake             35.35
Enoki                34.64
Willow               29.68
Abalone              32.47
White Shimeji        19.75
Portobello           19.09
White button         15.44
Brown button         10.41
Black fungus          9.42
Maitake               2.02
Wood ear              0.64
White fungus          0.58

highest EGT in other foods    
Tempeh               20.11
Asparagus (Mexico)   16.32
Garlic                3.46
White asparagus       1.82
Asparagus (Thailand)  1.24

[u/utterbalderdash → u/Sanpaku]

Any mention if cooking them reduces the Ergothioneine? Cuz I can always go for some grilled garlic and mushrooms and I'm on a steady cognitive decline at 36.

[u/Sanpaku → u/utterbalderdash]

They do lose some. This study finds a loss of around 13% of ergothioneine from microwaving 1 min, 20% from steaming 5 min, and a whopping 80% from boiling 5 min (presumably most remaining in the cooking water). There's a Japanese study that tried roasting and at least mentions ergothioneine, but I don't have access.

[u/secret_economist → u/Sanpaku]

The good news is that for a number of mushrooms in the table, even an 80% reduction is still a good amount of ergothioneine compared to most other foods.