Katy Perry has said becoming a goodwill ambassador for the UN children's agency has made her realise there's more to happiness than material possessions and social status.
She said that on her first trip for Unicef to the impoverished Indian Ocean island nation of Madagascar in April to see how the agency worked before agreeing to be a goodwill ambassador, she was moved by "the incredible joy" among the children despite the difficulties many faced.
"It changed my life," Katy said of the trip. "It really kind of reprioritised my thinking, and my whole approach on life, and how to find my own joy and my own happiness that isn't being from material possessions and social status."
She said it also inspired her to write Unconditionally, her favourite song on her new album Prism.
Unicef executive director Anthony Lake officially appointed her a goodwill ambassador to focus especially on children and adolescents who are most vulnerable as a result of severe poverty, violence, abuse and neglect.
"We look forward to hearing her 'roar' on behalf of Unicef," Lake said.
Katy said the Madagascar trip made her realise that young people outside the United States need help with education and other services that Unicef provides.
"It's nice to be able to pop the bubble that I live in and realise that the world has so many different things to offer and cultures," she said.
The chart star said listening to the stories of the people she met, especially the women who were suppressed and abused, had an influence on her and her music.
"You know I was going through a transition in my life where I felt like I had been suppressed and emotionally toyed with - and like I went there, and I was like, I have nothing to compare my situation to," she said in an apparent reference to the break-up of her marriage to British comedian Russell Brand. "It made me feel very grateful, but also very aware."
Katy said she expects to make one trip a year for Unicef and among the possibilities being discussed are Peru, Haiti and the Philippines.
Grammy nominations are coming up this week and there's been speculation that Katy's hit Roar could be up for some awards.
"Well first comes the speculation, then the nomination and then hopefully an award," she said. "So I think I would be too premature. I'm just happy that Roar has kind of taken on a life of its own and touched so many people in a way unexpectedly that I could have ever imagined."
Katy said there is definitely one other person she'd like to see get a Grammy nomination.
"I think my boyfriend would be a perfect candidate because he put out an incredible record called Paradise Valley that is unlike anything else in the scene right now," Katy said of singer John Mayer.