Why do we get old and sick?

Raj Persaud talks to Professor Volter Longo about his new book 'The Longevity Diet.' Could you live to 120 years old? Is all disease just a manifestation of a more fundamental biological process referred to ageing? Why do we get old and get sick? A revolutionary new approach to ageing and disease is being pioneered by one of the foremost authorities on longevity Dr Valter Longo. Dr Raj Persaud interviews him about his latest research and new book. Professor Longo's research suggests that living to 120 is entirely possible and that the average human lifespan could end up being 110 if the right diet and lifestyle is followed.