Ian Cheney and Curt Ellis can trace their roots back to a couple of patches of Iowa soil their respective great-grandpappies used to own, and one day both guys figured, hey, what better way to see where they’d come from than to retrace their relatives’ muddy footsteps in the cornfields. What Cheney and Ellis found wasn’t the family tree but its cornstalk—which reaches into everything most Americans eat and drink, for better or worse (the worse part, usually). Directed by Aaron Wolf, this is a twofold journey: the story of how two college buddies learned about their agricultural heritage; and the tale of how kernels of corn have invidiously worked their way into America’s diet—through the cows who’re literally overdosing on the stuff (and that is one nasty sequence) and the soft drinks sweetened with a syrup the men find impossible to manufacture in a kitchen without damned near blowing up the house. A worthy companion piece to Super Size Me and Fast Food Nation (more the book than the movie), King Corn will put you off corn for a long, long time; that Coke can will start looking like a hand grenade after a while, and, really, forget that burger for now. But this is as much a thoughtful meditation on the plight of the American farmer as it is a rant against our expanding waistlines; amazing how something as small as a kernel of corn wound up as dangerous as it is delicious.