Ben Foster took drugs to help him get into character for his role as Lance Armstrong in 'The Program.'

The 34-year-old actor took performance-enhancing drugs, under the supervision of his doctor, to give him a better understanding of the disgraced Tour de France winner.

He told the Guardian newspaper: ''For my investigation it was important for me privately to understand it. And they work. Even discussing it feels tricky because it isn't something I'd recommend to fellow actors.''

He added: ''There's a lot of fallout. Doping affects your mind. It doesn't make you feel high ... I don't know how to separate the chemical influence from the psychological attachment I had to the character. If it's working, it keeps you up at night.''

Ben's co-star Chris O'Dowd has defended his decision to take drugs to better his performance, branding it ''smart.''

He told the BBC: ''I think that's a really smart thing and makes sense ...

''I'm not advocating that you [should take drugs for a role], but I'm sure it probably wouldn't hurt your performance.''

Armstrong won the Tour de France seven consecutive times between 1999 and 2005, but was wiped of the titles in 2012 after he admitted, following a doping scandal, that he'd used performance-enhancing drugs to better his performance.

'The Program', which follows the rise and fall of the former sportsman's career, will hit UK cinemas on October 16.

A US date for the screening is yet to be released.