Love of sweets and genes

Yana Khlyustova, "Newspaper.Ru»  

Genes are responsible for the fact that it is so difficult for some sweet tooths to give up harmful treats, scientists have found out. Department of Science "Newspapers.Ru" figured out exactly how people perceive sweet and bitter tastes, and also found out how excess weight prevents you from losing weight. 

Many people who want to lose weight have faced a problem: a clear understanding of the need to reduce the consumption of sweets does not always help to do this. This often leads to the fact that both the overweight sufferers themselves and their relatives begin to blame the weak character of a person and his insufficient desire to lose weight for the problem. 

A group of researchers from Australia and the USA, led by Professor Liang-Dar Hwang, decided to find out what determines people's perception of the taste of sweets. It turned out that our attitude to desserts is influenced not by gastronomic habits formed during life, but by genes. 

More information about the results of the scientists' work can be found in the journal Twin Research and Human Genetics (Hwang et al., A Common Genetic Influence on Human Intensity Ratings of Sugars and High-Potency Sweeteners). 

The study involved 243 pairs of homozygous and 452 pairs of heterozygous twins, as well as 511 people without siblings. Each participant was asked to try four sweet substances – glucose, fructose, aspartame (a sugar substitute known as the food additive E951), as well as a sweetener called neohesperidine dihydrochalcone (NHDC, or Dihydrochalcone Neohesperidine), obtained from citrus plants. 

Scientists paid special attention to the identification of the dependence of the perception of sweet taste on human genes. It is worth noting that homozygous twins have an almost identical genotype, since they develop from one egg, which divides into two parts after fertilization. The genes of heterozygous twins developed from two different eggs are similar by about 50%.

As a result of the work, it turned out that genetic factors affect 30% of the differences in people's perception of sweet taste. 

It is the genes that explain the fact that the same cake or a glass of tea with sugar may seem superfluous to one person, and not sweet enough to another. In addition, it turned out that the perception of the natural sugars glucose and fructose and their artificial substitutes aspartame and DC neohesperidine depends equally on the genetic portrait of a person. 

Daniel Reed, one of the authors of the study, comments on the results as follows: "Consuming too much sugar is often perceived as a weakness of character. However, the results of our work prove that the perception of sweet taste is already "embedded" in our genetic portrait. Just as people born with poor hearing turn on the radio at full volume, so those who were born with genes that interfere with the normal perception of sweets add an extra spoonful of sugar to tea or coffee just to taste it." 

The results of the work also explained why, with age, people begin to show a predilection for sweeter food and drinks: every year of life worsens the perception of sweet taste by 2-5%.

Another group of American scientists from the State University of New York at Buffalo, led by Catherine Medler, found out that the perception of sweet taste depends on another factor, namely the weight of a person. More information about the researchers' findings can be found in the journal PLoS ONE. 

Scientists conducted experiments on mice, 25 of which were of normal weight, and 25 were obese, resulting from an unbalanced diet. As a result of the work, it turned out that the number of taste receptors responsible for the perception of sweets decreases in overly fat rodents, and those receptors that remain begin to work much worse.

While researchers cannot say why this is happening, however, it is still possible to draw a definite conclusion from the results of the work. It turns out that the presence of excess weight creates a kind of vicious circle that prevents you from losing weight: the deteriorating perception of sweet taste prevents overweight people from reducing its consumption. 

If we add to this the findings of the research group of Liang-Dar Hwang, it becomes clear: only really strong-minded people who are able to cope with both genetics and the consequences of other physiological processes occurring in the body can change their diet and reduce the amount of sugar in food.

However, sweet is not the only taste, the perception of which depends on genetics. Previous studies have shown that the ability to taste bitter has become an important step on the path of human evolutionary development. 

This was found out by a group of researchers led by Michael Campbell from the University of Pennsylvania. The scientists' article was published in the journal Molecular Biology and Evolution. 

In the course of the work, the genetic data of people living in Africa were studied. Representatives of African populations were chosen because this continent is the place of appearance of the first modern type of man. Scientists have studied the evolution of the TAS2R16 gene, which is responsible for the work of the salicin-sensing taste receptor. Salicin is a bitter–tasting substance found in many nuts, fruits and vegetables. 

Scientists have found out that the mutation of the TAS2R16 gene, thanks to which a person began to feel bitterness better, originated in people of East African populations about 1.1 million years ago. 

According to the authors of the work, this ability has significantly helped a person to better distinguish poisonous or spoiled foods from safe food: quite often a bitter taste serves as a kind of signal that the plant is unsuitable for food.

Professor Daniel Reed said that he and his colleagues are going to continue working on the study of sweet taste and find out which genetic mechanisms are responsible for its perception. 

"In the previous decades, quite a lot of research has been conducted aimed at studying the genetic basis of the perception of bitter taste. We will try to find similarities in the DNA of those people who have a weak susceptibility to sweets," the scientist promised.

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20.07.2015