Cassava (san) is a root vegetable. It sustained much of Vietnam during war and famine. It's used in the production of starch and that controversial fifth flavour, MSG, and to make textiles and paper. That doesn't say much for either its nutritional value or its taste now, does it? Oh, and cassava's fed to pigs, its propogation causes erosion and it can and has killed humans.
I ate some last night.
At dusk, convoys of blanket head-banded cassava merchants wheel it out, their bike boxcarts hauling coal braziers, giant aluminium pots and kilos of the root, all lit by battery powered fluoro-tubes. During the peak hours, in packs they shrewdly ply their tubers parallel to traffic jams where the ride-by trade is rapid. Later on they pedal solo, often the only bright glow in a dark street.
Eaten raw, cassava can put one six feet under. Cooked, scattered with shredded coconut and salty peanut dust, it's not a bad belly filler, satisfying like a spud. It certainly put fire in the belly of Vietnam's soldiers in the wars they waged against the French and Americans.
Cassava is a quick carbo fix, a worthy thu hai (number two) extreme cheap street eat, at 5000VND (USD31c, AUD42c) a bagful.