Another example is our taste for sweetness. Carbohydrates are all broken down to glucose for supplying essential energy to our cells. The quickest natural source of glucose to be absorbed is fructose in fruit, which tastes sweet to us. So we crave sweet things. Even sweeter is sucrose in sugar. The discovery of sugar cane in the Caribbean was the original impetus for the creation of the slave trade and the source of the wealth that built some of our finest country houses, such was the European enthusiasm for sugar.

But again that taste works against us today, now that sugar is so cheap. The rapid rise in blood glucose after a sugary meal provokes a big rise in insulin release because this hormone enables the glucose to enter cells or be converted into fat for storage. This reaction is adaptive for the rare occasions when your heart and brain need a rapid "hit" of glucose in emergencies and again thrifty genes were beneficial for converting chance discoveries of ripe fruit into stored fat. But the four sugary drinks a day that some children now drink from the Coke dispenser conveniently sited in the school corridor are too many. Not only do the children get fat but so much insulin release reduces the cells' sensitivity to it and so diabetes, obesity, high blood pressure and high lipids (fats) ensue. This greatly increases the risk of heart disease and blood vessel catastrophes in the brain-strokes.

Salt used to be rare and expensive, as it is not often found in the ground and requires technology and manpower to extract from the sea. Hence the word "salary" derives from the Latin for salt. However, other than water, 90 per cent of the contents of the body fluids bathing our cells is salt. So we have a strong taste for it and very efficient mechanisms for conserving it, but very few ways of getting rid of it. Modern foods exploit our salt taste, so we eat on average 11g a day, when we should be eating no more than 6g. Since salt is such a major constituent of our body fluids, the more salt we have on board the more fluid we have. The more fluid we have in our blood vessels the higher our blood pressure will be. So that too feeds into the metabolic syndrome and helps to explain why roughly one-quarter of all males now have dangerously high blood pressure.