The Tantalizing Tale of Taste
Written by Krithi Iyer and Aparna Iyer
Most great scientific discoveries and inventions often started as a mistake. This was no different in the strange mystery of genetics and taste. It all started with a curious, yet unsuspecting chemist. Arthur Fox. Fox was working in his lab with phenylthiocarbamide, or PTC. Several of his colleagues were also busy at work. Fox accidentally blew the PTC into the air, and some of his colleagues complained about the taste of it. The other colleagues and himself were perplexed by their complaints. They couldn’t taste anything. This accidental lab experiment started a chain of research into the genetics behind taste.
Our specific food preferences are based off three different factors: the environment, prior experience with the food, and genes. Our genes change our ability to perceive food, as in, how strongly we smell and taste certain flavors. Receptors in our tongue and nose detect certain taste and scents. However, each receptor can only detect one flavor or scent. When something sour is eaten, or smelt, only the “sour receptors” can detect this aroma or flavor. The other receptors, like sweet or bitter, will be unable to taste or smell the sour molecules. Both our nose and our tongue play a key role in tasting. Our brain also plays a key role in combining both the smell and taste to form a unique flavor.
In total, we have 35 different receptors to detect sour, salty, sweet, bitter and umami flavors. However, we have a large sum of 400 different receptors to detect smell. All of these different receptors are created by our genes. Interestingly enough, these receptors are located in mutational hotspots. Meaning, they have a higher likelihood of getting a mutation. This causes genetic variation in these receptors across humans, so we all perceive different flavors. In each individual, there is at least a 30–40% difference in these receptors.
The Genetics Behind the Main Tastes
Some of us are chocolate and ice cream lovers, while others wonder how one can eat so much sweet. Our ability to taste sweetness, and also bitterness, is controlled by our genes. We have two different gene receptors for sweetness: TAS1R2 and TAS1R3. Within these two genes, there are high variations in both sweet and bitter receptors. Meaning, this gene varies in its ability to perceive the intensity of these flavors. Those who find ice cream too sugary, might have a more intense perception of sweetness. Our genes are one third of the factors that influence whether or not we like sweetness.
Bitter on the other hand, tends to be a more common enemy. We generally all tend to dislike bitter flavors as an acquired evolutionary tool. Most poisonous berries or fruits had a more bitter flavor. Those that didn’t have a problem with bitter, ate the berries and died. The others’ distaste for its flavor prevented us from eating them. We have a certain gene to thank for this. The gene receptor for bitterness is TAS2R38. It also controls our ability to detect PROP or propylthiouracil and the more commonly known PTC, or phenylthiocarbamide. Both PROP and PTC are chemical compounds. They are both commonly found in greens such as brussels sprouts and broccoli. The allele for being able to taste PTC and PROP is dominant, so people with the gene are called Tasters. Whether or not we can taste PTC groups us into two common categories, among five others: Tasters, and Non-Tasters. Tasters have a tendency to dislike more bitter foods, which comes from being able to taste the bitter flavor that PTC and PROP give off, particularly greens such as Brussel sprouts, while the Non-Tasters don’t mind these flavors as much.
Exactly like bitter and sweet flavors, the sour taste also depends on our genes. Researchers at the Monell Chemical Senses Center determined this by a simple method. Twins. The scientists gathered together 74 pairs of identical twins and 35 pairs of fraternal twins. They then determined the lowest concentration of sour these twins could taste. Since identical twins share all their DNA, and fraternal twins only share about 50%, the results of the test conveyed a very interesting result. The pairs of identical twins had a higher number of similar answers to one another than the fraternal twins. Since they share all their genes, it was concluded that the perception of sour was also genetic. However, possibly the most interesting outcome of this test was the variability in sour perception. While our genes constitute about 33% of our sweet perception, our genes constitute a full 53% in our perception of sour. However, the catch is, the genetics do not change our taste bud’s ability to perceive salty and sour tastes. Rather, our genetics varies the number of taste buds we have, which in turn changes our responsiveness to both sour and salty flavors.
While our liking for salt is also based off genetics, a research study conducted, came out with surprising findings. 87 people, 45 men, and 42 women were tested with several different salty foods over a course of multiple weeks. Supertasters, people, who taste flavors stronger, generally tend to like more salt. This is what confused the researchers. Wouldn’t someone who felt flavors more intensely be repulsed from large quantities of salt? The answer actually had to do with the bitter flavor. Bitter tends to be a very disliked flavor. This is no different for supertasters. Since they can taste the bitter flavor more intensely, adding more salt to their food covers up the strong bitter taste. Surprisingly enough, the opposite of supertasters also preferred adding more salt. Non-tasters, those who aren’t able to taste subtle flavors very well, also add more salt. The reason for this, of course, is unsurprising. Since non-tasters aren’t able to taste salt as well, they add more, just to be able to taste it.
A common misconception that many people have is that spice (from chilies and such) is a taste. It is not. Spice is in fact a combination of feelings in your mouth that are caused by capsaicin, a substance found in most chili peppers. Our taste buds have many nerves in them, and there are some called nociceptors and thermoreceptors. Nociceptors are receptors for pain while thermoreceptors detect changes in temperature. When you eat a chili, or something with chili in it, the capsaicin is absorbed by the tongue and it enters the taste bud. It irritates the nociceptors which causes the burning feeling in our mouths. Capsaicin also stimulates the thermoreceptors, which creates the hot feeling you get when eating something spicy. How much your tongue burns is based on how much damage or irritation is being caused to the nociceptors and the number of taste buds you have. If you have a greater number of taste buds, more of the nociceptors will be damaged, which is one of the reasons that supertasters are much more affected by spice. Umami, the “savory” flavor, is controlled by two genes. One of which, also controls the sweet receptor. Both TAS1R1 and TAS1R3 control our umami receptors. How our umami flavors differ is very similar to the sweet and bitter receptors.
The OR6A2 Gene
Cilantro is one of the most well-known herbs in the world, but it is definitely not one of the most well-liked. In fact, a lot of people actually think that cilantro tastes like soap, but this is actually due to a genetic variation in their bodies. People have a gene called OR6A2 in their bodies, that encodes for a receptor. This receptor helps people pick up on the scent of aldehydes, which are several different compounds found in things like flowers, cinnamon and perfumes. They are also found in soap and cilantro. So, the mutation in the OR6A2 gene makes some people think that cilantro and soap taste and smell the same.
The Different Types of Tasters
As discussed earlier, the ability to be able to taste PROP is a dominant trait. If you have it, you are considered a taster. Being a non-taster means you are unable to taste PROP, and it is a recessive trait. The alleles for being a taster are PAV/AVI and the alleles for being a non-taster are AVI/AVI. However, there is also an allele of PAV/PAV. These people are known as supertasters, and they are extremely sensitive to flavors. The confusing thing about this, is there are two separate groups. There are just tasters and non-tasters for being able to taste PROP. However, there are supertasters, tasters, and non-tasters in general. Supertasters are much more sensitive to flavors, and non-tasters are the exact opposite. However, all supertasters can also taste PROP. Surprisingly, the ratio of tasters and non-tasters varies vastly across the world. In Chinese, West African, and Japanese regions, the number of non-tasters is lower than 3 percent. 30% of people in North America are non-tasters, and about 32.8% of people in India are non-tasters.
The average number of taste buds on the human tongue ranges from 2,000 to 8,000. But this number can vary for many people. Non-tasters typically have less than the average number of taste buds, or a low number in the average range of taste buds, on their tongues. They struggle with being able to taste anything in their food. This causes them to need a lot of spice and salt in their food to be able to detect any flavor at all. Tasters have a stronger response to flavors in food which comes from the increased amount of taste buds they have on their tongues. Supertasters on the other hand have more than the average number of taste buds or a number in the average range of taste buds, on their tongue. This causes them to be very sensitive to food and makes it much more difficult to eat foods with strong flavors due to how intense it tastes.
How Depression Affects Taste
In our bodies, we have many neurotransmitters. There are two called serotonin and noradrenaline. Neurotransmitters are chemicals that allow for messages to be sent to and from the brain. Serotonin helps with regulating pain and moods, while noradrenaline helps with regulating sleep. When people face things such as depression, extreme stress or anxiety, their levels of both these chemicals drop. In a study conducted at the University of Bristol, researchers had a group of people, none of them being depressed, taste solutions with the flavors of bitter, sweet, sour and salty. All of them were easily able to identify these tastes. After this, the taste tests were administered once more after the patients had taken Roboxetine and Paxil. Both Roboxetine and Paxil are anti-depressants. Paxil increases the levels of serotonin while Roboxetine increases the levels of noradrenaline. The results of the tests showed that after taking Paxil, the patients were able to detect bitter and sweet flavors at a much lower concentration than before. After taking Roboxetine, the patients were able to detect sour and bitter flavors at a much lower concentration. This gave some backing towards the idea that conditions such as depression and anxiety could affect how people taste things. Furthermore, this research helped show that there is a possibility that taste tests on people with depression could help determine the right anti-depressant for them, based on what neurotransmitter is having more influence over them.
Our genes impact how and what we eat much more than we realize. Taking a bite of food seems so simple, but in reality, it’s really much more complicated than that. Our genes make up who we are, and also, what we taste. We are all unique, our taste buds included. Like how we can never truly see from someone else’s perspective, we can also never taste like someone else. Our genes combine together to create a unique tasting experience for us all. But, knowing this, we can use it to our benefit. Being able to identify that you prefer salty foods, or sweet foods, can allow for you to choose a diet that suits you, and helps you remain healthy. Changing your tasting needs so you don’t require as much salt, or sugar, to satisfy your taste buds, can result in an overall healthier population.
Sources:
Bachmanov, Alexander A, et al. “Genetics of Taste Receptors.” Current Pharmaceutical Design, U.S. National Library of Medicine, 2014, www.ncbi.nlm.nih.gov/pmc/articles/PMC4764331/.
Barclay, Eliza. “Are Women Better Tasters Than Men?” NPR, NPR, 31 Aug. 2015, www.npr.org/sections/thesalt/2015/08/31/427735692/are-women-better-tasters-than-men.
Bramen, Lisa. “The Genetics of Taste.” Smithsonian.com, Smithsonian Institution, 21 May 2010, www.smithsonianmag.com/arts-culture/the-genetics-of-taste-88797110/.
Buckingham, Cheyenne. “How Your Genetics Influence Your Taste Buds.” Eat This Not That, Eat This Not That, 21 Feb. 2020, www.eatthis.com/genetics-and-taste-buds/.
Cheriyedath, Susha. “Genetics of Taste.” News, 25 June 2019, www.news-medical.net/health/Genetics-of-Taste.aspx.
D. Zohary, M. Hopf, et al. “A Genetic Variant near Olfactory Receptor Genes Influences Cilantro Preference.” Flavour, BioMed Central, 1 Jan. 1970, flavourjournal.biomedcentral.com/articles/10.1186/2044–7248–1–22.
DNAFit. “Can Genes Affect Your Taste?” DNAFit, DNAFit, 10 Jan. 2019, www.dnafit.com/advice/nutrition/can-genes-affect-your-taste.asp.
The Editors of Encyclopaedia Britannica. “Phenylthiocarbamide Tasting.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 13 May 2008, www.britannica.com/science/phenylthiocarbamide-tasting.
Fushan, Alexey A., et al. “Allelic Polymorphism within the TAS1R3 Promoter Is Associated with Human Taste Sensitivity to Sucrose.” Current Biology, Cell Press, 25 June 2009, www.sciencedirect.com/science/article/pii/S0960982209012548.
Fushan, Alexey A., et al. “Association between Common Variation in Genes Encoding Sweet Taste Signaling Components and Human Sucrose Perception.” OUP Academic, Oxford University Press, 21 July 2010, academic.oup.com/chemse/article/35/7/579/337259.
Gardner, Amanda. “Love Salt? You Might Be a ‘Supertaster’.” CNN, Cable News Network, 16 June 2010, www.cnn.com/2010/HEALTH/06/16/salt.taste/index.html.
Hwang, Liang-Dar, et al. “A Common Genetic Influence on Human Intensity Ratings of Sugars and High-Potency Sweeteners: Twin Research and Human Genetics.” Cambridge Core, Cambridge University Press, 17 July 2015, www.cambridge.org/core/journals/twin-research-and-human-genetics/article/common-genetic-influence-on-human-intensity-ratings-of-sugars-and-highpotency-sweeteners/371FA1FE567F3ECA1745B5946D3D9126.
Ishti. “Did You Know That ‘Spicy’ Is Not a Taste?” Owlcation, Owlcation, 13 June 2016, owlcation.com/stem/Did-you-know-that-spicy-is-not-a-taste.
Kim, Un-kyung, et al. “Positional Cloning of the Human Quantitative Trait Locus Underlying Taste Sensitivity to Phenylthiocarbamide.” Science, American Association for the Advancement of Science, 21 Feb. 2003, science.sciencemag.org/content/299/5610/1221.long.
Mainland, Joel D, et al. “The Missense of Smell: Functional Variability in the Human Odorant Receptor Repertoire.” Nature News, Nature Publishing Group, 8 Dec. 2013, www.nature.com/articles/nn.3598.
Nicholas Archer Research Scientist. “Blame It on Mum and Dad: How Genes Influence What We Eat.” The Conversation, 5 Nov. 2019, theconversation.com/blame-it-on-mum-and-dad-how-genes-influence-what-we-eat-45244#:~:text=A%20recent%20twin%20study%20found,in%20the%20detection%20of%20bitterness.
P. Rozin, TA. Vollmecke, et al. “Genetic Predisposition and Taste Preference: Impact on Food Intake and Risk of Chronic Disease.” Current Nutrition Reports, Current Science Inc., 1 Jan. 1986, link.springer.com/article/10.1007/s13668–012–0021–3.
Partner, Carolina Teaching. “Genetic Differences Affecting Taste and Smell.” Carolina Knowledge Center, www.carolina.com/knowledge/life-science/genetic-differences-affecting-taste-and-smell.
Pirastu, Nicola, et al. “Association Analysis of Bitter Receptor Genes in Five Isolated Populations Identifies a Significant Correlation between TAS2R43 Variants and Coffee Liking.” PLOS ONE, Public Library of Science, journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0092065.
Pirastu, Nicola, et al. “Genetics of Food Preferences: A First View from Silk Road Populations.” Wiley Online Library, John Wiley & Sons, Ltd, 13 Aug. 2012, onlinelibrary.wiley.com/doi/abs/10.1111/j.1750–3841.2012.02852.x.
Sandell, Mari A., and Paul A.S. Breslin. “Variability in a Taste-Receptor Gene Determines Whether We Taste Toxins in Food.” Current Biology, Cell Press, 18 Sept. 2006, www.sciencedirect.com/science/article/pii/S0960982206020616.
“Sour Taste Make You Pucker? It May Be In Your Genes.” ScienceDaily, ScienceDaily, 13 July 2007, www.sciencedaily.com/releases/2007/07/070712135115.htm#:~:text=Scientists%20report%20that%20genes%20play,for%20sweet%20and%20bitter%20taste.
“TAS2R38 Gene — Genetics Home Reference — NIH.” U.S. National Library of Medicine, National Institutes of Health, ghr.nlm.nih.gov/gene/TAS2R38#resources.
Tepper, Beverly J., et al. “NYAS Publications.” The New York Academy of Sciences, John Wiley & Sons, Ltd, 4 Aug. 2009, nyaspubs.onlinelibrary.wiley.com/doi/abs/10.1111/j.1749–6632.2009.03916.x.
“Why Some People Tolerate Spicy Foods Better than Others.” Office for Science and Society, 31 Oct. 2019, www.mcgill.ca/oss/article/did-you-know/why-do-some-people-spicy-foods-not-others#:~:text=Spicy%20foods%20contain%20a%20chemical,tongue%20called%20a%20TRPV1%20receptor.&text=This%20variance%20may%20be%20one,spice%2C%20and%20others%20love%20it.\
