Clean eating – whether it is called that or not – is perhaps best seen as a dysfunctional response to a still more dysfunctional food supply: a dream of purity in a toxic world. To walk into a modern western supermarket is to be assailed by aisle upon aisle of salty, oily snacks and sugary cereals, of “bread” that has been neither proved nor fermented, of cheap, sweetened drinks and meat from animals kept in inhumane conditions.