Usher has urged his protege Justin Bieber to eat well and take care of himself - to ensure his voice doesn't change too much as he grows into a man.

The Yeah! hitmaker has been mentoring the 16 year old since they met in 2008 and they share the same singing coach to keep their vocals in top condition.

But Usher has warned the teenager - who pulled out of a gig in New York last month (Aug10) after a health scare - he needs to look after himself.

Usher tells Access Hollywood, "We're taking the right steps to make sure that he didn't lose too much (ability to hit high notes). It's all about what you eat and really just taking care of yourself."