"It is what you think it is," the former Disney star told MTV. "There's a disclaimer at the top of the script that basically says, we're doing it for real. And anything that is 'illegal' will be shot in blurred images. But other than that, everything is happening."
Other well-known mainstream films featuring unsimulated sex acts include 2006's Shortbus, and 2003's The Brown Bunny, which contains an infamous fellatio scene between Vincent Gallo and then-(maybe)-girlfriend Chloë Sevigny.
Nymphomaniac, which will be broken up into two parts, follows the sexual development of a woman (Gainsbourg) from birth to adulthood. Stellan Skarsgård and Nicole Kidman have also been tapped to star.