To Taste or Not to Taste

1. To Taste or Not to Taste

2. The Genetics of Taste • Taste is perceived in taste receptors on the tongue surface, commonly known as taste buds. • The ability to distinguish between different chemicals in food and drink is crucial for the survival of humans and all other animals. • Thus, individuals who perceive an unpleasant taste when attempting to ingest harmful foods are more likely to survive and reproduce.

3. Taste Perception • Not all humans have the same perception of bitterness for some substances. An example is (PTC) and propyl-thiouracil (PROP). • Such compounds are for instance found in cabbage and rapeseed. • Some people perceive no particular taste of these compounds ("non-tasters"), whereas others experience an extremely unpleasant bitter taste ("tasters"). Among tasters there is also variation, in that some tasters (so-called "super-tasters") are extra sensitive to bitterness.

4. Gene Frequency for Tasters • The frequency of tasters and non-tasters varies considerably among human populations. • The frequency of non-tasters ranges from 3% in West Africa; 6-23% in China, 40% in India and is estimated to be around 30% in people of European descent.

5. Location of the Gene • The cause of differences in the perception of PTC-like compounds among humans has been traced to genetic variants in the TAS2R38 gene on chromosome 7. • The C allele is dominant, so having one copy is enough to have the perception of a bitter taste

6. Types of Genes • On the other hand, if you have the T allele of this SNP on both copies of chromosome 7, then you have about an 80% chance of being a "non-taster" of bitterness in response to PTC-like compounds. • This means that foods that may taste bitter to others taste far less bitter to you. It is thought that about 20% of the variation in bitter taste perception of these compounds is explained by other genetic variants.

7. How Does This Work • The presence of either one of these genes changes the shape and number of the receptors on tongue so that the bitter tasting chemicals are more likely to bind and sweet chemicals have fewer receptors so the sweet taste is less intense.

8. Advantages and Disadvantages • Taste perception and the genetically determined human response to bitter-tasting foods may also have a considerable effect on nutrition and health. • Studies have for example found that the non-taster genotype is a predictor of increased alcohol consumption in adults and also associated with lower preferences for sweetness in children and may therefore reduce their likelihood of dental decay.

9. Advantages and Disadvantages • Studies have also found that "supertasters" find some foods too bitter to enjoy, for example grapefruit, coffee and tea, brussel sprouts and cabbage. • The research showed that people can be really sensitive to the bitterness of grapefruit juice, but not at all sensitive to alcohol, and vice-versa, Hayes noted. • “Bitter tastes are sensed through different pathways.

10. Opposition in Your Brain • Since bitter and sweet are in opposition in the brain • If you experience more bitterness from a food, you also perceive less sweetness. This means not all foods taste the same to all people." • They may also be more sensitive to sweetness and much less likely to tolerate hot and spicy foods.