That "Food, Inc." is available to those of you who have Netflix. It is one of their Play-in-now options, so you don't even have to wait for it to come in the mail.
About a year ago, Adam and I watched another "food" documentary (of sorts) called "Super-size Me." I'd say that it is definitely less scientific; one guy decides to see what happens when he eats NOTHING but McDonald's food for a month (I think it's a month; was it 6 months? Surely, SURELY, it was only a month!) Anyway, it's appalling to watch, and a bit shocking to see the health effects on this young man, in such a short time.