Fatal Attraction of Tasty Food

Human bodies are simply not built to consume the unhealthy diet we eat nowadays

John Stein

A rising tide of obesity and the diseases it causes threatens to bankrupt the NHS. Thirty per cent of US women are now on diets. Jamie Oliver’s healthy school meals go down like a lead balloon. The US food supplement market hit $15 billion last year. What is up with our nutrition?

Well, actually, it all started 10,000 years ago with the invention of agriculture. Contrary to received opinion, this may have been a bad mistake. Agriculture makes it possible for a few peasants to feed thousands and the excess wealth that this generates enables a more leisured class to develop arts, culture and technology. These, in turn, encourage the growth of cities so that different crafts can benefit each other and trade between them. But cities spawn a ruling class, kings and absent aristocratic landowners to exploit everyone, together with diseases and disasters fanned by proximity, and wars to steal each others’ wealth.

Not only did agriculture generate these questionable benefits, but it also left us with a dependence on farmed cereals and animal products. However, we were not evolved to eat them. Homo sapiens evolved close to, if not in, water and the mainstay of our diet was sea food. Twenty per cent of the whole brain and half of heart cell membranes consist of a single “polyunsaturated” fatty acid (PUFA), docosahexanoic acid (DHA), which is mainly acquired by eating oily fish such as tuna, mackerel or salmon, or shellfish. Fish, rather than mammals, together with the fruits and roots that paleolithic man ate in abundance, provided us with most of the calories and proteins that we needed together with all the essential vitamins, minerals and fatty acids that we have to get from our diet. Moving into cities, and away from water, greatly limited supplies of these.

Nevertheless, until mid-Victorian times, the food even the poor ate was not actually dangerous. Fish, fruit and vegetables were cheap. Armies of hugely powerful navvies, paid only sixpence a day, built our canals and railways. They were not malnourished. If you survived the infections of childhood, your life expectancy was very similar to today’s, despite all our medical advances. But over the last century, fish has become very expensive and even though fruit and vegetables remain relatively cheap, nobody wants to eat them. The reason? The industrialisation of food production has enabled tasty foods that were rare to become cheap and these have changed our eating habits drastically.

During our evolution, “thrifty” genes that gave their owners competitive advantage in times of scarcity, were selected. Animal fats, which are “saturated” rather than unsaturated fatty acids, provide the most energy calories of any foodstuffs. So genes tended to be selected that provided people with a taste for animal fats together with efficient fat stores to squirrel them away. The difficulty of hunting animals meant that meat was rarely on the menu. But those with thrifty genes would particularly benefit from those rare occasions. Hence they are prominent in our genetic heritage, particularly among races that evolved in harsh environments, such as native Americans or Australians. However, this works to their disadvantage nowadays because saturated fats derived from corn or soya are now so cheap and plentiful. So the genes that allowed a girl to accumulate fat in the summer to provide her and her baby with nourishment in the winter now cause her to put on more and more weight. That weight greatly increases her chances of diabetes, heart disease or a stroke, unfortunately not that far in her future.

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.

Cheaply satisfying our taste for sweet, salt and fat has not only led to increased heart and blood vessel disease, but reduced our appetite for fish, fruits and vegetables. These contain “micronutrients”, essential fatty acids, vitamins and minerals, which are also essential for healthy heart and brain. At the age of 30, Hugh Sinclair, a brilliant biochemist at Magdalen College, Oxford, helped to persuade the Second World War government to provide free cod liver oil, malt extract and orange juice to all pregnant mothers and their children to counteract the deficiencies he’d found in the diets of East Enders. He said that the average Brit’s diet then, despite the food shortages, was far better than now.

Most of us eat far too few fruits and vegetables and hardly any fish. We have therefore been rewarded with a rising tide not only of cardiovascular disease, but also of impaired brain function. This causes impaired cognition and lack of self-control, which spawns industrial inefficiency, social instability and violence. Small studies in vulnerable groups have suggested that giving people daily capsules containing the most important micronutrients could help reverse our deteriorating intelligence and literacy, inattention, impulsiveness, violence and even ward off Alzheimer’s. Perhaps we should return to Hugh Sinclair’s policy of giving them to everyone.

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