The evolutionary roots of the human ’sweet tooth’
April 14th, 2008 by admin
Humans love the taste of sugar so much that the word “sweet” refers not only to this basic taste quality but also something that is highly desirable or pleasurable. This attraction goes so far that sugar (and sugar-rich foods) overconsumption is probably the main factor driving the current obesity epidemic.
But why are we so fond of sugar, when other animals appear to be so ’self-restrained’ when it comes to diet and nutrition? The answer seems to lie on our evolutionary history. Refined sugars (e.g., sucrose, fructose) were absent in the diet of most people until very recently in human history. Biologists speculate that the human attraction for intense sweetness results from an inborn hypersensitivity to sweet tastants (molecules that taste sweet). In most mammals, including rats and humans, sweet receptors evolved in ancestral environments poor in sugars. Being able to detect carbohydrate-rich nutrients constituted an advantage that was selected favourably as it allowed to choose foods more effective in providing energy. However, natural foods are usually sugar-poor, so our ancestors were not not adapted to the high concentrations of sweet tastants present in our present-day products that contain refined sugar or corn syrup.
Overconsumption of sugar-dense foods or beverages is initially motivated by the pleasure of sweet taste and is often compared to drug addiction. French investigators attempted to explore this relationship by using rats that were offered either sweetened water or highly addictive doses of cocaine. The results were stunning: the vast majority of the rats (94%) preferred the sweet treat over the drug, demonstrating that intense sweetness can surpass cocaine reward, even in drug-sensitized and -addicted individuals.
A plausible explanation for the addictive power of sugar is that the supranormal stimulation of the sweet receptors by sugar-rich diets, such as those now widely available in modern societies, would generate a supranormal reward signal in the brain, with the potential to override self-control mechanisms and thus to lead to addiction.
Category: Weightloss, General health, Obesity, Medicine, Addictions, Diabetes, Biology | No Comments »
