Yep, 18 months is about the minimum for running/jogging. And be careful with long walks too. Really, your pup should be getting the vast majority of it's exercise from playing.
As JVZ boxers has pointed out, you risk doing permanent damage to joints and ligaments that aren't fully developed before that age. Hip dysplasia, for one, is thought to have an environmental component (it's not just a genetic thing) and can really ruin your dog's life.
As a general rule, anything that can be considered as 'forced exercise' should be avoided with a puppy until such time as it's growth plates have completely closed. That just happens to be at around 18 months, hence that age as the recommended minimum
'Forced exercise', incidentally, is any form of exercise where the dog isn't going to take short frequent rests and pauses. It will rest for brief periods when playing, it won't when it is trying to keep up with you on a leash walking or running. And that sort of constant pressure is what does the damage. You can do a search here on 'forced exercise' if you want more information - there's plenty of it
