LONDON — With even Silicon Valley worrying about the effect of technology exposure on young people, Britain’s top doctors on Thursday issued advice to families about social media and screen use. Their prescriptions: Leave phones outside the bedroom. Screen-free meals are a good idea. When in doubt, don’t upload. And get more exercise.

“Technology can be a wonderful thing,” Britain’s chief medical officers, who hold advisory positions similar to that of the surgeon general in America, wrote in a document published on Thursday. “But too much time sitting down or using mobile devices can get in the way of important, healthy activities,” they said.

The medical officers declined to set age and time limits, saying that there was not enough evidence to do so. The American Academy of Pediatrics gave more specific guidelines in 2016, urging parents to keep infants under 18 months away from screens and to restrict the time young children spend using media.

Reports from Silicon Valley last year suggested that even people at the cutting edge of digital technology worried about their own children’s exposure to screens. Some families there have hired nannies to keep their children offline.