What is the Genetics of taste?
Why many dislike bitter: a matter of genes
BY PAOLO GASPARINI
The perception of chemicals in the external environment has always been of fundamental importance for the survival of individuals and species. Taste is the sense that allows all animals to locate food and avoid predators or the ingestion of toxic substances. Moreover, taste has a decisive influence on the degree of acceptance of a substance, which is directly proportional to the pleasantness of the taste sensation. For example, sweet substances, a source of energy for the body, usually give a pleasant sensation, while the bitter taste, typical of most poisons, causes an unpleasant sensation and rejection of the substance.
Humans can identify five main tastes: bitter, sweet, sour, salty and umami. In addition, a sixth taste has recently emerged, fat, which is responsible for the perception of fat molecules in food.
With regard to bitterness, various compounds present in food such as amino acids, peptides, esters, lactones, phenols, polyphenols, flavonoids, terpenes, methylxanthines (caffeine), sulphimides (saccharin), etc. stimulate the perception of this taste quality.
Studies on the genetics of bitter taste began by chance in 1931 when a British researcher synthesised a chemical compound belonging to the thioureas family, PTC (phenylthiocarbamide), and dispersed crystals in the air. Some of his colleagues perceived a strong bitter taste, while he perceived nothing at all. This initial observation was followed by several studies showing that the ability to perceive PTC, or a similar compound called PROP (propylthiouracil), varies from individual to individual and even from population to population.
This different perceptive capacity is a typical genetic character transmitted from parents to children.
In 2003, the gene responsible for the perception of the bitter taste of PTC or PROP, called TAS2R38, was identified.
A different ability to perceive the bitter taste of PTC or PROP was associated with differences in food preferences and choices. Testers, who are more sensitive to bitterness, do not prefer foods such as cruciferous vegetables (cabbage, broccoli, Brussels sprouts, turnips, etc.), those containing caffeine, quinine, isoumulones (beer bitterness), naringin (grapefruit). They are also more sensitive to the perception of spiciness and fat due to the greater presence of trigeminal nerve endings on the tongue and in the oral cavity. Obviously, 'non-tasters' tend to behave in a completely opposite way.