Transcript To Taste or Not to Taste - University of Mississippi

To Taste or Not to Taste
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.
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.
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.
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
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.
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.
Advantages and Disadvantages
• Taste perception and the genetically
determined human response to bittertasting 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.
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.
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.