Heritable differences in chemosensory ability among humans

Abstract

The combined senses of taste, smell and the common chemical sense merge to form what we call 'flavor.' People show marked differences in their ability to detect many flavors, and in this paper, we review the role of genetics underlying these differences in perception. Most of the genes identified to date encode receptors responsible for detecting tastes or odorants. We list these genes and describe their characteristics, beginning with the best-studied case, that of differences in phenylthiocarbamide (PTC) detection, encoded by variants of the bitter taste receptor gene TAS2R38. We then outline examples of genes involved in differences in sweet and umami taste, and discuss what is known about other taste qualities, including sour and salty, fat (termed pinguis), calcium, and the 'burn' of peppers. Although the repertoire of receptors involved in taste perception is relatively small, with 25 bitter and only a few sweet and umami receptors, the number of odorant receptors is much larger, with about 400 functional receptors and another 600 potential odorant receptors predicted to be non-functional. Despite this, to date, there are only a few cases of odorant receptor variants that encode differences in the perception of odors: receptors for androstenone (musky), isovaleric acid (cheesy), cis-3-hexen-1-ol (grassy), and the urinary metabolites of asparagus. A genome-wide study also implicates genes other than olfactory receptors for some individual differences in perception. Although there are only a small number of examples reported to date, there may be many more genetic variants in odor and taste genes yet to be discovered.Keywords: Flavor, Genetics, Evolution, Taste, Odor, Receptor, Polymorphism Review Why we differ in taste perceptionHumans use several kinds of information to decide what to eat, and the combination of experience and sensory evaluation helps us to choose whether to consume a particular food. If the sight, smell, and taste of the food are acceptable, and we see others enjoying it, we finish chewing and swallow it. Several senses combine to create the idea of food flavor in the brain. For example, a raw chili pepper has a crisp texture, an odor, a bitter and sour taste, and a chemesthetic 'burn.' Each of these sensory modalities is associated with a particular group of receptors: at least three subtypes of somatosensory receptors (touch, pain, and temperature), human odor receptors, which respond either singly or in combination; [1,2], at least five types of taste receptors (bitter, sour, sweet, salty, and umami (the savory experience associated with monosodium glutamate [3])), and several families of other receptors tuned to the irritating chemicals in foods, especially of herbs and spices (for example, eugenol found in cloves [4] or allicin found in garlic [5]). The information from all these receptors are transmitted to the brain, where it is processed and integrated [6]. Experience is a potent modifier of chemosensory perception, and persistent exposure to an odorant is enough to change...

Tissue dependent expression of bitter receptorTAS2R38mRNA

“…The subjects themselves were markedly different too, healthy young subjects in the first study and older patients studied here. However, the relationship between TAS2R38 genotype and PTC bitterness was clear, and consistent with many other sensory studies of T2R38 ligands [9, 39–42]. Even with these caveats, the results show clearly that deficiencies in the sensory testing, if present, were not large.…”

Do polymorphisms in chemosensory genes matter for human ingestive behavior?

“…Other specific anosmias are thought to have a genetic basis, but here we focus on several examples especially relevant to food. Data on isovaleric acid (cheesy) and urinary metabolites of asparagus are reviewed elsewhere (Newcomb, Xia, & Reed, 2012). …”

On Variability & Human Consciousness

“…Heritability estimates explained between 20 and 50 percent of the variance in most cases (see also (Mogil, 2012). Additionally, some emergent evidence suggests that variation in the experience of certain tastes and flavor profiles may also be partly heritable (Newcomb, Xia & Reed, 2012).…”