See: http://www.foodexplorer.com/product/HISTORY/FF04719.HTM

Also, from:  Following from Wild Seasons. Gathering and Cooking Wild
Plants of the Great Plains. Kay Young. University of Nebraska Press. Lincoln
and London. 1993

"One more caution: although most persons can eat Jerusalem artichokes
perfectly well, some experience flatulence and mild to acute abdominal
distress, regardless of whether the tubers are raw or cooked. This is
because the tubers contain inulin, a carbohydrate that not everyone digests
easily. Many grocery stores now carry cultivated forms of Jerusalem
artichokes or a hybird by the name of sunchoke, but I have yet to find a
wrning on a single package. To be safe, try only a small portion of
Jerusalem artichoke the first time to determine wether you can or cannot eat
these tubers--and certainly, do not serve them to unadvised guests.
(pages283-284)"