What are your thoughts about lion's mane supplementation to slow the decline or improve cognitive capacity for those at risk of dementia?

Lion's mane is the latest in the ever-evolving list of supplements that have a whiff of animal data, very small human trials, or frankly, anecdotal evidence. A decade ago, it was coconut oil; last week, it was lithium. There will always be suggestions of the benefit of this or that. Currently, there are no randomized controlled human trials that would suggest a benefit for Lion's mane. I do not recommend this (or lithium, or prevagen, or neuriva, or ...) at this time.