The dairy industry acknowledges (as Hippocrates did) that some people are allergic to milk - though this makes it sound as if the problem lies in the individual’s aberrant constitution, rather than in the beverage itself. Yet, when you look at it more closely, the extent of lactose intolerance is extraordinary. Lactose is the sugar in milk, and it needs to be broken down by the enzyme lactase that lives in our intestines and bowels. If the lactose we absorb is greater than our lactase capacity, undigested lactose travels to the large intestine, where it ferments, producing gas, carbon dioxide and lactic acid. The result? Bloating, cramps, diarrhoea and farts. In 1965, investigators at Johns Hopkins found that 15% of all the white people and almost three-quarters of all the black people they tested were unable to digest lactose. Milk, it seemed, was a racial issue, and far more people in the world are unable than able to digest lactose. That includes most Thais, Japanese, Arabs and Ashkenazi Jews, and 50% of Indians.