American film maker Robert Kenner's "Food, Inc." is a hard-hitting expose of the agribusiness.
It looks through the eyes of farmers, consumers and legislators, contrasting corporate images of red barns and white fences with factory farms and huge processing plants.
Kenner said he tried but failed to get the companies themselves -- such as Monsanto, Smithfield Foods and Tyson Foods-- to give their side of the story in his film.
"We hoped to have a dialogue with the companies about the challenges of feeding us," Kenner told the audience. "We reached out to the companies. They seemed interested but in the end almost all said no, they didn't want to be involved."
His documentary looks at poultry sheds and meat packing plants. There are disturbing shots of cattle feed lots and animals heading for slaughter. It critically examines the corn subsidies that allowed the agribusiness to become so large and the synthetic fertilizers, herbicides, and hormones used.
The United Nations says food production is the main cause of pollution and the destruction of ecosystems because of the massive use of chemical pesticides and fertilizers.
The film, first screened at Toronto in September, is expected to be released in the second half of 2009 in the United States by Magnolia Pictures and Kenner said the international rights were being sold in Berlin's European Film Market.
"The film is ostensibly about food but it's also about the concentrated power in the United States and the corrupting effects of that power," said Eric Schlosser, author of "Fast Food Nation". He is in the film and also spoke as a panelist.
"But it's not only the United States, you also see the same tendencies in the European Union. It's a real threat to ordinary people when one company has so much control."