Brad Pitt's new film "cuts to the base of our humanity".
The 49-year-old star produced '12 Years a Slave' - based on the story of a black man, Solomon Northup, who was kidnapped and sold into slavery in 1841 - after he was left mortified by the true events the movie is based on.
He told Ann Curry on NBC News' 'TODAY' show: "It's one of those few films that ... cuts to the base of our humanity.
"And it was not until I saw Solomon Northup's story that I fully, fully grasped the utter horror of losing your freedom or denying another one their freedom, taking their freedom, splitting their family apart. It's why I got into film in the first place."
Brad is on screen for a short period but claims he plays a minor supporting role, while the real stars of the film had to endure particularly emotional scenes during filming.
He explained: "I'm there to support the story. The main performances are Chiwetel Ejiofor, Lupita Nyong'o and [Michael] Fassbender. These are such demanding parts. These guys had to keep themselves in just this perpetual state of angst and foreboding and longing. And they did it."