OK! Interview: Alicia Keys

For Alicia Keys, something actually is in the water. The music superstar is the latest to join the growing list of celebs – including 50 Cent and Jennifer Aniston – endorsing Vitamin Water.

"I don't partner with anybody, but this really was natural for me because I've been a fan from the beginning," she told OK! at Madison Square Garden before departing on her European tour with Jordin Sparks. Her signature flavor is the lemonade-like Multi-V, which touts vitamins from A-Z. But Alicia has a deeper reason for signing with the beverage company.

"I love their personality," she said. "Have you ever read the bottles? Don't you just feel naturally smarter when you read it?"

To stay fit, the singer sticks to a diet of egg-white omelets, oatmeal, fish, veggies and brown rice, but she has to be careful about when she eats.

"One time I ate right before going on stage and I had to hide my belches from the microphone - that was funny!"

Alicia took a more serious approach when OK! asked her about her trip to Africa and her involvement with AIDS prevention organization Keep a Child Alive.

"There are so many stories to tell and so many things going on in the world, and when you're able to see it first-hand, I think it gives you a more empathetic feeling about it. I felt like I want to dell everybody I could about what I'd seen and the way we could erase it and prevent it."

For the complete interview with Alicia, pick up the latest issue of OK!, on newsstands now!