Fall through mid-winter sunchokes consist mainly of inulin, a complex starch that humans CAN'T digest, but fart-making bacteria can eat just fine.
Blast, my understanding was that the bacteria finally do break it down into something digestible. Perhaps not very efficiently.
http://en.wikipedia.org/wiki/Inulin#Fate_in_vivoGood to know that they are more digestible in late winter, though. I had read that they are best following the first hard frost.