I first became aware that for every ill there is a natural cure when I was 5. My maternal grandmother, who was a force of nature and, although loving to the point of obsession, could be terrifying at the best of times, would chase me round the garden and shovel spoonsful of some nasty concoction – made of egg yolk whipped to a froth with sugar – down my throat, because in her mind, I was too thin and anemic.