A study by the National Institutes of Health in the US suggests that mobile phones could have an effect on the brain.
They reported higher sugar use in the brain, a sign of increased activity, after 50 minutes on the phone.
The research published in the Journal of the American Medical Association said the clinical significance was unknown.
Experts in the UK said there was no suggestion of a health risk.
Since the boom in mobile phone use, there has been considerable interest in the effect on the body.Read more