Portman produced and narrated the film, which is based on Jonathan Safran Foer's book of the same name, and looks at how animals are abused within the factory farming complex.
Eating Animals makes an argument against factory farming, featuring footage from both intensive facilities, and smaller 'family-run' businesses.
Co-producer Foer described the approach to the film as being 'open' to different viewpoints, telling Vanity Fair: "We would talk about, what is the tone that will make this very difficult subject approachable?
"Because people are so disinclined to approach it, to willingly say, 'I'm going to upset myself for 90 minutes. You're gonna tell me this thing I love, it's probably not good for me or anybody else. It's counterproductive to be holier than thou."
According to a review by Variety, this approach translates into showcasing small scale livestock farmers as 'the most compelling figures in the film...who have sidestepped the industrial-farming system to raise their own meticulously cared-for chickens, turkeys, and hogs'.
It adds: "Eating Animals understands the boutique economics of what it's showing us. It knows that heritage farms like these represent just one percent of the farmers in America, an elite group who have subverted the system and are keeping an old idea of farming alive.
"The other 99 percent have been sucked into the exhausting competitive juggernaut of factory farming, in which farms raise animals on a scale of mass production, which requires conditions that are called, euphemistically, 'confinement agriculture' but might more accurately be described as an animal holocaust."
A clip from Eating Animals
Because of the welfarist slant, one vegan who saw a preview of the screening when it launched in the US last year revealed to Plant Based News that they were disappointed by the movie.
"It feels like a missed opportunity. There is only one way to end the horror of animal exploitation - and that is to go vegan," they said.
"The way I interpreted it, this film was suggesting that eating animals from higher welfare farms was a really positive step fowards - but as we know even animals from more 'humane' farms are slaughtered to satisfy human appetites.
"It would be impossible to feed the planet on animals reared in the better conditions on some of the farms shown. A stronger message would have been to avoid animal exploitation entirely."