Unlocking the mystery of taste

Why do we like or dislike certain foods? Is it cultural, psychological, or learned? Does our physical makeup have an effect? Or is it some combination thereof? Whatever the reason, one thing is certain: Taste preference is subjective—and highly personal.

The mechanics of flavor

Taste begins with our perception of five basic types: sweet, salty, bitter, sour, and savory (“umami”). Humans have anywhere from 2,000 to 4,000 taste buds, found in those little bumps (papillae) on our tongue, plus in other areas of our mouth, throat, and nose. Each taste bud has 10 to 50 taste-receptor cells connected to nerve fibers that transmit taste signals to our brain1,2. Contrary to what we’ve been taught, there aren’t specific areas of the tongue that are responsible for certain tastes. In fact, all areas of the tongue can detect all taste types—although the sides and back are more sensitive.
To decipher flavors, which are far more complex, our brain combines the information from our taste buds with our sense of smell. Temperature, texture, and even color add further dimension to how something tastes and whether or not we enjoy it. To begin to understand the various possible flavor combinations, scientists have created a taste-intensity scale of 1 to 10 for each of the five basic tastes. When also factoring in temperature, mouthfeel, and smell, it makes for tens of thousands of possible flavor experiences.
Taste-receptor cells die and are replaced about once every 10 days3. As we age, the number of taste buds we have decreases, and those that remain tend to shrink and become less effective at their job. This likely explains why certain foods taste more intense to children and why we can tolerate stronger (and stranger) flavors as we get older.

Survival tastes good

Smell and taste are chemical-detecting senses that are connected to our autonomic nervous system, which is responsible for regulating the functions of our internal organs. This is why good tastes and smells can make our mouths water, and why bad tastes and smells can make us nauseous. The former response is our digestive system firing up, and the latter is our body’s way of saying “Avoid!”
Umami, identified in 1908 by a Japanese researcher, refers to that savory flavor found in meat-based protein, mushrooms, tomatoes, and rich broths. Umami taste receptors detect glutamate, an amino acid that makes food taste more delicious2. Interestingly, umami may be one of the earlier tastes experienced by infants due to high levels of glutamate in breast milk4. It’s not surprising we’ve evolved to appreciate rich-tasting foods.
Being able to detect bitterness is also a survival mechanism—because toxins in poisonous plants usually taste bitter. Humans have about 30 genes that code for bitter taste receptors, making us better equipped to avoid ingesting harmful substances5. The backs of our tongues have a higher concentration of bitter taste receptors specifically to help make sure we spit out something poisonous instead of swallowing it1. As a counterpoint, animals that are strictly herbivores have fewer bitter taste receptor genes, otherwise their food supply would be too restricted. Instead, they have larger livers capable of breaking down toxic compounds.
Still, some people like bitter-tasting foods, while others have a strongly negative reaction to them. Is there something else going on?

DNA plays a part

There are easily dozens, maybe hundreds, of genes that affect how well we detect certain flavors and consume foods5. For example, to some people, cilantro tastes like soap (or worse). This is, in part, because of a variant of the olfactory-receptor gene OR6A26, which is coded to detect aldehydes—found in cilantro, soap, and stinkbugs. Another example is a variant of SLC2A2, a glucose-sensing gene that has been linked to some people having a sweet tooth. Normally, our brains send out a signal that we’re satiated when appropriate glucose levels have been met. People with the SLC2A variant are less capable of regulating what they eat based on the amount of glucose they’ve consumed, and they tend to eat more sweets7.
Discovered in 2003, TAS2R38 is a gene that codes for a taste receptor capable of sensing the bitter compound phenylthiocarbamide (PTC)8. In this case, it’s all about the shape of the physical taste receptor and how well PTC can (or can’t) bind to it. People with at least one copy of a certain variant for this gene have the ability to taste PTC to some degree, and those with two copies of a different variant can’t taste PTC at all. People who can’t taste PTC are more likely to enjoy foods like broccoli and cabbage, while those who can may perceive these vegetables as too bitter and shy away from them.

It’s personal

Ultimately, DNA doesn’t have the final say in what foods we like or dislike. Our genes might have us wired to experience tastes a certain way, but when it comes to preference, there’s evidence that culture can play a role. A perfect example of this is vanilla: In the West, we typically use vanilla in sweet foods, and so when we taste vanilla, it enhances our perception of sweetness. This is not so in parts of Asia, where they use vanilla in savory foods.
Food preferences can also be learned. Babies in the womb can actually taste what their mothers eat, and even learn to prefer those particular flavors early on9,10. We can also train ourselves to like certain things—like coffee without sugar, for example. And of course, many of us have had a bad experience that made us dislike (sometimes irrevocably) a food or drink we used to enjoy. Ultimately, we like what we like, but our tastes change with time.

1“How does our sense of taste work?” Pubmed Health.Institute for Quality and Efficiency in Health Care. Aug. 16, 2016. Web. 19 Oct. 2017.
2Roper, Stephen D., and Nirupa Chaudhari. “Taste buds: cells, signals and synapses.” Nature Reviews Neuroscience, vol. 18, no. 8, 2017, pp. 485–497., doi:10.1038/nrn.2017.68. Web. 19 Oct. 2017.
3Hamamichi, R., et al. “Taste bud contains both short-Lived and long-Lived cell populations.” Neuroscience, vol. 141, no. 4, 2006, pp. 2129–2138., doi:10.1016/j.neuroscience.2006.05.061
4Mennella, Julie A et al. “Early Milk Feeding Influences Taste Acceptance and Liking during Infancy.” The American Journal of Clinical Nutrition 90.3 (2009): 780S–788S. PMC. Web. 19 Oct. 2017.
5Bachmanov, Alexander A. et al. “Genetics of Taste Receptors.” Current pharmaceutical design 20.16 (2014): 2669–2683. Print.
6Eriksson, Nicholas, et al. “A genetic variant near olfactory receptor genes influences cilantro preference.” Flavour, vol. 1, no. 1, 14 Aug. 2012, p. 22., doi:10.1186/2044-7248-1-22.
7Julliard, A-Karyn et al. “Nutrient Sensing: Another Chemosensitivity of the Olfactory System.” Frontiers in Physiology 8 (2017): 468. PMC. Web. 19 Oct. 2017.
8Risso, Davide S. et al. “Global Diversity in the TAS2R38 Bitter Taste Receptor: Revisiting a Classic Evolutionary PROPosal.” Scientific Reports 6 (2016): 25506. PMC. Web. 19 Oct. 2017.
9Mennella, Julie A., Coren P. Jagnow, and Gary K. Beauchamp. “Prenatal and Postnatal Flavor Learning by Human Infants.” Pediatrics 107.6 (2001): E88. Print. Web. 19 Oct. 2017.
10Beauchamp, Gary K., and Julie A. Mennella. “Flavor Perception in Human Infants: Development and Functional Significance.” Digestion 83.Suppl 1 (2011): 1–6. PMC. Web. 19 Oct. 2017.