The idea that more natural food – food which hasn’t been transformed by human and industrial intervention – is best for us is a powerful one. Psychologists have found a strong preference for that which is “natural”, even when people differ in what they understand that term to mean. But naturalness is a muddle – we are often signalled by advertising to see heavily manufactured foods as “natural”; the pioneers of cereal manufacturing were the greatest advocates of “natural” food in the early 20...