Valentina Zelyaeva

It's a lot harder to stick to my regime when I'm travelling, so when I'm home, I make sure that when I wake up in the morning, I drink one litre of water with lemon to cleanse my body from the inside, and then I'll have a big jar of vegetable juice.

As a young surgeon in training at the University of California San Francisco General Hospital in the early '80s, my colleagues and I were inundated with an epidemic of young men with fevers, rashes, swollen lymph nodes and eventually death.