I track my reaction time daily, and I was surprised to find that I got faster after I started taking metformin (brand name: Glucophage) for pre-diabetes. Reaction time is known to be correlated with cognitive ability, so it's possible that metformin may have nootropic properties. The drug is also reported to have other benefits, such as increasing longevity and preventing neurodegenerative diseases.
Seth Roberts was an innovator, a teacher, an original thinker -- and he was an inspiration to me. I'm reminded of the Grateful Dead t-shirt that says, "They aren't the best at what they do. They're the only ones who do it".
I've been following his Shangri-La diet for over four years now. Here's a page about my results, although it's a bit out of date: