Bex June 10, at 8:
Homo sapiens first appeared aboutyears ago At this stage we were still hunter-gatherers, out looking for food rather than growing and rearing our own supplies. These modern hunter-gatherers tend to be shorter and lighter than their urban cousins but still need to consume far more calories due to the additional energy expended in finding food.
The ability to adapt our diet has been essential to the human migration from the warmth of Africa to the cold of the Arctic north and the arid heat of the deserts. Why the preference for a high fat diet? Calories are essential for energy.
Every cell in the body produces energy by the process of respiration and respiration needs a constant supply of glucose. Fat can store twice as many calories per unit weight than proteins are carbohydrates.
If food was scarce it would literally have been survival of the fattest! We seem to learn at a very young age which foods are high in calories and we develop a taste for these.
Gibson and Wardle found that the calorific value of food was the best predictor of whether or not a child would like that food. Fats are very useful for energy. A given amount of fat contains about twice the calories of similar amounts of protein or carbohydrate. In our historical past, fats would have been relatively rare.
As a result fat would have been relished and cherished! Today, in contrast fat is everywhere, but unfortunately we have not lost that preference for it and as a result we consume it in huge and dangerous amounts.
This comprised some meat, fish, fatty oils, fruit and veg. Fatty foods would have provided the calories along with vitamins A and D whilst the fruit and veg would have provided a few carbohydrates and vitamins B and C.
Compared to modern diet however, carbohydrates would have been in short supply.
Some believe this move away from our ancient diet with a much greater reliance on carbs has led to increased incidence of hypertension, CHD and obesity. Why the preference for sweet foods?
In some ways the answer to this is obvious. Sweet indicates presence of sugar which indicates calories needed for energy. Sweetness would be associated with foods that are ripe and foods that are ripe are going to contain more sugar.
Rozin thinks this preference for sweetness is innate. Bell et al gave sweet foods to Eskimos in Alaska. Under normal conditions Eskimos have nothing sweet in their diet. However, the foods were readily accepted despite their novel nature, again suggesting an underlying human preference for sweet foods.
Again a genetic predisposition is evidence of evolutionary pressure to like sweet foods.
Sugar placed on the tongues of newborn babies produces positive facial expressions again suggesting the preference for sweet is there at birth Steiner Zhao et al identified two specific genes, T1r2 and T1r3 which code for sweet receptors on the tongue.
The fact that these genes exist and have been maintained within the population again provide powerful biological evidence for an adaptive preference for sweet foods. This would seem to be supported by the number of sweet receptors on the human tongue, far more than for the other flavours such as bitter, sour, salt and umami.
People of all ages and of all cultures seem to prefer sweet taste to any other, suggesting it is an inherited preference: Meiselman et al Finally, humans go to extreme lengths and risk danger to secure sweet food.
Members of the Bayaka Pygmy tribe of Africa climb high trees and suffer stings from hundreds of angry bees to provide this sweet food for their families. Why the preference for salty foods? Salt is essential for the functioning of muscles and nerve cells action potentials and all that.
Homeostasis keeps salt levels reasonably constant. However, salt is not readily available naturally, so like fat when it was found by our ancestors it would have been much prized, hence the reason for us liking it so much. Some have suggested that our desire for salt is innate, we do after all have salt receptors on the tongue.
By four months of age, children being breastfed which contains very low levels of salt prefer cereals that are salty.
People with natural sodium deficiency find salt even more palatable than the rest of us and eat it in larger quantities when available. Dudley et al found that ants living further inland with less salty soils prefer salty foods to sweet.
Again these studies suggest that we instinctively know that we need salt and have developed mechanisms that ensure we get sufficient.I went to a dinner party at a friend’s home last weekend, and met her five-year-old daughter for the first time.
Little Maya was all curly brown hair, doe-like dark eyes, and adorable in her shiny pink nightgown. The best opinions, comments and analysis from The Telegraph.
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