Could a genetic test tell you your likely food preferences? Are supertasters made or born? When you try to convince your friend to try guacamole are you fighting their bias or their DNA? These are just some of the questions being asked and answered by biologists studying the complex and often surprising science of taste.
Today’s biotechnologies allow scientists to study the genetics of taste and even identify the specific genes behind our food likes and dislikes. Here we highlight four tantalizing taste genes. But first a quick background on the biology of taste.
Taste Genetics 101
Our varied and often impassioned food preferences are shaped by three major interacting factors: environment, prior experience, and genetics. The environment includes everything from a person’s cultural heritage to the weather during a particular meal. It even includes the microbiome in your mouth! (Turns out those bacteria secrete enzymes that strongly influence taste signals on our tongues.) Prior experiences include all an individual’s positive and negative encounters with food. This influence skews negative. Evolution has equipped us to naturally avoid things that make us sick even if it means a lifetime of disliking cotton candy after a single dizzying carnival ride! Finally, there’s genetics. Food preferences are believed to have a heritability factor that ranges from 20% (for desserts) to 44% (for fruit and veggies) to 70% (for some proteins).
If asked most people would respond that their food preferences boil down to taste. Taste comes from a combination of signals from the mouth and nose. In the mouth, humans have about 35 receptors (proteins that receive and transduce signals for cells) that detect one of five tastes – sweet, sour, salty, bitter, and umami. In the nose around 400 highly specific receptors work together to detect and distinguish aromas. Both sets of receptors bind to molecules in the external environment and then generate a nerve impulse that travels to a part of the brain called the gustatory cortex. The GC then combines all the signals it’s receiving into what we interpret as taste. In some cases, taste is also influenced by physical data such as the coolness of ice cream or the burn of a certain spice.
Every receptor protein is coded for by DNA. Scientists have found that many nose and mouth receptor genes are mutational hot spots. When a mutation occurs in these areas it changes the shape of the receptor protein which in turn alters how a person perceives a certain flavor and aroma. A 2013 study found that around 30% of odor receptor alleles differed between individuals. This high variability means that each of us uniquely interprets the foods we all eat. Hence, while the basic genetic and taste system of humans is the same, our tastes are not.
Genes that Influence Taste
There are many taste genes currently being studied and more are discovered every year. Can’t start a pint of ice cream without finishing it? It might be due in part to a mutation in the FGF21 gene. This gene codes for a protein that influences the neural feedback loop associated with wanting more and more sugar once you taste something sweet. Enjoy your coffee strong and dark? This might be partly due to a specific nucleotide sequence in your TAS2R43 gene. This gene codes for a protein that helps you detect certain bitter flavors.
Four of the most famous (and well-studied) flavor genes are TAS1R2, TAS1R3, TAS2R38, and OR6A2.
TAS1R2 and TAS1R3: One of our species’ strongest and most universal likes is for sweet-tasting things. Both evolutionary biologists and nutritionists have long been interested in the molecular biology behind this desire. At the cellular level, our sweet detecting ability is largely controlled by a single receptor protein called TAS1R2/3 that’s found in cells at the tip of our tongues. Unlike many receptor proteins, TAS1R2/3 is versatile and able to detect a wide range of sweet-tasting compounds including sucrose, fructose, saccharin, dulcin, guanidino acetic acid, aspartame, and glucose. This protein is coded for by a pair of genes found on human chromosome 1 named TAS1R2 and TAS1R3. These two genes have also been found in many other animals suggesting that they are unique and essential nucleotide sequences. At the same time, scientists have discovered important variations in these genes in humans. For example, a 2017 study showed that children who were homozygous for an SNP change in the TAS1R2 gene consumed fewer calories from sugar. In another study, variations in the TAS1R3 gene were linked to differing abilities to detect sugar in adults.
TAS2R38: Scientists have also discovered genes link to our differing abilities to detect the opposite – bitter tastes. Supertasters are a subset of the population who are particularly sensitive to certain bitter tastes. Rough estimates suggest that around 25% of the population qualifies as a supertaster while another 25% can be classified as a non-taster who find foods less bitter but also less favorable. This wide range is partly due to differences in the density of taste buds on people’s tongues. However, it’s also been linked to a mutation in the gene TAS2R38 that seems to increase sensitivity to the bitter-tasting chemical 6-n—propylthiouracil (PROP). This chemical is found in many foods but particularly broccoli, spinach, Brussel sprouts, turnips, coffee, beer, and chocolate. Because of their sensitivity to this compound, supertasters often avoid these foods or mask the bitter taste with salt, sugar, or fat.
OR6A2: Few flavors seem as divisive as cilantro also known as coriander. Cilantro haters (who even have their own online forum at www.IHateCilantro.com) report that this herb has a rotten smell and strong soapy taste that can completely ruin any dish it’s added to. Scientists think that a single nucleotide mutation in the olfactory receptor gene 6A2 (OR6A2) may be partly responsible. In a 2012 study, they discovered that individuals with this mutation were highly sensitive to several aldehydes found in coriander. (Aldehydes are organic compounds with a soapy taste and smell). However, other genes may also be involved including TRPA1 which codes for an ion channel in cells that senses pain and cold, GNAT3 which codes for a guanine nucleotide protein found in several taste receptors, and TASSR50 which codes for a protein that mediates the perception of bitterness.
Interested in finding out more? This 2019 review article is a great place to start with several tables highlighting key genetic studies focused on bitter, sweet, fat, umami, salty, and sour tastes. Even better explore the genetics of taste in the lab! Check out our hands-on laboratory experience Exploring the Genetics of Taste: SNP Analysis of the PTC Gene Using PCR. Find out more about this popular experiment here.