Okinawa, Japan is famously one of the world's five "blue zones" and much ink has been expended on figuring out why. Bitter gourd or certain types of seaweed, perhaps?

What's less often discussed is that it's also Japan's poorest prefecture to this day, with spotty record keeping since it was effectively a Japanese colony (it was previously the Ryukyu Kingdom, which was annexed by Japan in 1879). Vast slabs of the main island were razed to the ground during the WW2 Battle of Okinawa and much of the civilian population simply starved to death.

I remember a paper from last year in which they are suggesting that basically Blue Zones are made just by a combination of clerical error and pension fraud: https://www.biorxiv.org/content/10.1101/704080v3

"Blue zones" are debunked bullshit.