Can’t Stand IPAs? The Answer May Lie in Your Genetic Sensitivity

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The India Pale Ale is one of the most popular beer styles worldwide, but if, despite everything, you are one of those people who cannot stand hop-heavy beers, this could be due to a genetic variation in your perception of bitter taste.

It has been shown that some people have a taste receptor gene that makes them more sensitive to bitter flavors, but a study published in 2010 by Duffy, Hayes, and their team sheds new light on the relationship of this gene with our perceptions more generally.

Researcher John Hayes, a food scientist at Penn State University, sums it up this way.

What we have observed is that people differ in the way they perceive the intensity of bitterness.

The TAS2R38 gene

In 2003, a team of geneticists identified the TAS2R38 gene as responsible for much of the variation in how people perceive PTC, a bitter laboratory compound (Kim and colleagues, 2003). John Hayes and researcher Valerie Duffy, from the University of Connecticut, later studied how those differences influence what we eat.

Valerie Duffy believes she herself may lack the more sensitive version of this gene, and she explains it this way.

The idea of how you perceive bitter taste is linked to how strongly these compounds bind to the receptor, so when I eat bitter vegetables or Brussels sprouts, for example, they are naturally sweet to me.

Duffy’s hunch was that this could lead people to also avoid eating other types of vegetables. So she decided to put the theory to the test.

We recruited a group of volunteers and brought them to the lab to do taste tests with them and evaluate their sensitivities.

Specific tests were also conducted for the TAS2R38 gene, and participants were asked to record what they ate over several days and to complete a food frequency questionnaire.

Sensitivity to bitter taste

The results, published in 2010 in Chemosensory Perception with 59 participants, showed that people who are less sensitive to these bitter compounds reported eating more vegetables of all kinds than those who were sensitive.

While previous studies had already identified this association, the surprising aspect of these new findings is that it was shown that people who were highly sensitive to bitterness ate fewer vegetables in general, not just bitter ones.

Valerie Duffy puts it this way.

What we believe is that if a person feels that some vegetables are too bitter, they will tend to generalize this to all other vegetables, mainly green ones.

Duffy further suggests that there are multiple factors, both biological and environmental, that influence our choice of foods and beverages, including our own upbringing.

This variation in vegetable consumption has its molecular basis in the haplotypes of the TAS2R38 gene. PAV (Proline-Alanine-Valine) is the functional variant of the receptor for compounds containing the N-C=S chemical group, such as PTC and PROP (Bufe and colleagues, 2005), while AVI (Alanine-Valine-Isoleucine) encodes a less functional receptor.

Each person inherits two copies of the gene, so the most common combinations are PAV/PAV, PAV/AVI, and AVI/AVI. Their frequency varies by population, as two recent studies in Japan and Thailand show.

In Japan, moreover, the Yamaki study found no differences between genotypes in cruciferous vegetable intake, unlike earlier studies with participants from the United States and Europe.

None of these combinations amounts to being a supertaster. Hayes and colleagues showed in 2008 that the greater overall taste intensity that characterizes supertasters is not due to TAS2R38 variants.

The table below shows the frequency of TAS2R38 genotypes in those two populations.

Sensitivity vs. aversion

It is essential to distinguish between the biological ability to detect bitterness and the hedonic response (liking or disliking) toward it. Variants in bitter taste genes influence the intensity with which some compounds are perceived, and they do not automatically dictate preference. Hayes and colleagues found in 2011 that variants of the TAS2R16 and TAS2R38 genes did not explain either the sensory response to a Scotch whisky or how much people liked it.

A person can be genetically sensitive to bitterness and yet enjoy it if they have had prior positive exposures or if they associate that taste with pleasant experiences. Therefore, genetics loads the gun, but environmental and psychological factors pull the trigger of aversion.

Consumer adaptation

In conclusion, despite the current popularity of IPAs, the truth is that a couple of decades ago very few people drank them.

Beers that at that time were considered extremely hoppy, such as Sierra Nevada Pale Ale, are now considered quite “normal” for the taste of today’s consumer, who has become increasingly adapted to bitter taste.

Not all bitterness activates the gene in the same way

It is relevant for IPA drinkers that TAS2R38 is not the receptor that picks up hop bitterness. Intelmann and colleagues tested all 25 human bitter taste receptors in 2009 against 15 hop compounds, including alpha acids and iso-alpha acids.

All of them activated combinations of just three receptors, TAS2R1, TAS2R14, and TAS2R40. That is why the TAS2R38 version each person inherits serves as an indicator of their sensitivity to certain bitter compounds and does not, on its own, predict how much bitterness they will notice in an IPA.

Frequently Asked Questions (FAQs)

1. Can sensitivity to bitter taste be modified?

Repeated exposure to bitter flavors can increase tolerance and, in some cases, even make some people begin to enjoy them. This is known as sensory adaptation or taste learning.

2. What foods do people with bitterness sensitivity reject?

People who are more sensitive to certain bitter compounds tend to reject cruciferous vegetables, such as Brussels sprouts, and some bitter greens like arugula more often. The bitterness of coffee or grapefruit also varies with other bitter taste genes, according to a 2013 review by Hayes and colleagues.

3. Is there a genetic test to confirm this?

There are commercial genetic tests that include analysis of the TAS2R38 gene, which is related to bitterness perception. Specific taste tests can also be conducted in clinical or university settings. Knowing the genotype is not enough to tell whether someone is a supertaster, because that trait depends on more than TAS2R38.

4. How does culture influence taste acceptance?

Bitterness perception is also shaped by culture and upbringing. In some cultures where consumption of bitter foods is common from childhood (such as bitter herbal infusions or certain vegetables), people develop greater tolerance and liking for these flavors.

Bibliography

• Bufe, B., Breslin, P. A., Kuhn, C., Reed, D. R., Tharp, C. D., Slack, J. P., Kim, U. K., Drayna, D., & Meyerhof, W. (2005). The molecular basis of individual differences in phenylthiocarbamide and propylthiouracil bitterness perception. Current Biology, 15(4), 322-327. https://doi.org/10.1016/j.cub.2005.01.047
• Duffy, V. B., Hayes, J. E., Davidson, A. C., Kidd, J. R., Kidd, K. K., & Bartoshuk, L. M. (2010). Vegetable intake in college-aged adults is explained by oral sensory phenotypes and TAS2R38 genotype. Chemosensory Perception, 3(3-4), 137-148. https://doi.org/10.1007/s12078-010-9079-8
• Hayes, J. E., Bartoshuk, L. M., Kidd, J. R., & Duffy, V. B. (2008). Supertasting and PROP bitterness depends on more than the TAS2R38 gene. Chemical Senses, 33(3), 255-265. https://doi.org/10.1093/chemse/bjm084
• Hayes, J. E., Wallace, M. R., Knopik, V. S., Herbstman, D. M., Bartoshuk, L. M., & Duffy, V. B. (2011). Allelic variation in TAS2R bitter receptor genes associates with variation in sensations from and ingestive behaviors toward common bitter beverages in adults. Chemical Senses, 36(3), 311-319. https://doi.org/10.1093/chemse/bjq132
• Hayes, J. E., Feeney, E. L., & Allen, A. L. (2013). Do polymorphisms in chemosensory genes matter for human ingestive behavior? Food Quality and Preference, 30(2), 202-216. https://doi.org/10.1016/j.foodqual.2013.05.013
• Intelmann, D., Batram, C., Kuhn, C., Haseleu, G., Meyerhof, W., & Hofmann, T. (2009). Three TAS2R bitter taste receptors mediate the psychophysical responses to bitter compounds of hops (Humulus lupulus L.) and beer. Chemosensory Perception, 2(3), 118-132. https://doi.org/10.1007/s12078-009-9049-1
• Khimsuksri, S., Paphangkorakit, J., Pitiphat, W., & Coldwell, S. E. (2022). TAS2R38 polymorphisms and oral diseases in Thais: a cross-sectional study. BMC Oral Health, 22, 21. https://doi.org/10.1186/s12903-022-02043-2
• Kim, U. K., Jorgenson, E., Coon, H., Leppert, M., Risch, N., & Drayna, D. (2003). Positional cloning of the human quantitative trait locus underlying taste sensitivity to phenylthiocarbamide. Science, 299(5610), 1221-1225. https://doi.org/10.1126/science.1080190
• Yamaki, M., Saito, H., Mimori, T., Suzuki, Y., Nagasaki, M., Suzuki, K., Satoh-Kuriwada, S., Shoji, N., et al. (2023). Analysis of genetic polymorphism of bitter taste receptor TAS2R38 and TAS2R46, and its relationship with eating and drinking behavior in Japanese. Journal of Nutritional Science and Vitaminology, 69(5), 347-356. https://doi.org/10.3177/jnsv.69.347

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