I'm not usually in the habit of praising movies for being good for you. But "Food, Inc.," which is playing at Film Forum, is more than just a terrific documentary. It's an important movie, one that nourishes your knowledge of how the world works, or, in this case, has started not to work.

The filmmaker, Robert Kenner, features and builds on the muckraking testimony of authors Michael Pollan, who wrote "The Omnivore's Dilemma," and Eric Schlosser, who wrote "Fast Food Nation."

Building off of their insights, "Food, Inc." creates an essential, disturbing portrait of how the food we eat in America has become a deceptively prefabricated, and even hazardous industrial product.

Kenner does not rant, but rather connects the dots. Huge, aggressively-lobbied government subsidies for corn transformed farms into factories of mass-produced corn-fed cattle, which in turn are slaughtered and ground into "hamburger meat filler" that is cleansed with ammonia. All that so we can buy a double cheeseburger for 99 cents.

"Food, Inc." reveals how the assembly line techniques pioneered decades ago by the fast-food industry were then adopted everywhere else. The use of high fructose corn syrup in almost every supermarket product is part of the same system that masses chickens into concentration camp coops, where they are bred for their oversize, flavorless white meat. And you thought breast enhancement was just popular for humans.

A big-picture vision of corporate duplicity and control, "Food, Inc." is a hard movie to shake. Days after you've seen it, you'll find yourself eating something - a cookie, a piece of chicken, cereal out of the box, a perfectly round waxy tomato - and you'll realize you have virtually no idea what it actually is.