Are my slow-growing hair and nails down to a slow metabolic rate? If so, is it a bad thing?

The long-running series in which readers answer other readers' questions on subjects ranging from trivial flights of fancy to profound scientific concepts

My hair and nails grow about a quarter as fast as my wife's, so I wonder: is this because I have a slow metabolic rate? And if I have, is it a good or a bad thing?

Peter Hanson, Exeter