The diseases of ageing are already overwhelming health care facilities. In the decades ahead, our older populations will put even more pressure on health unless there are medical breakthroughs. These diseases are proving stubborn to medicate and cures are very rare. A human fountain of youth has yet to show itself. In other animals, things appear easier to treat with less complex biochemistry to get in the way. Dr Bloom explains to Dr Karl why a family of proteins called Sirtuins may hold some hope.