If the thought of sipping a beer is gag-inducing, you're not alone. But even if you're in good company, it begs the question: Why do some people hate the taste of beer?
The answer comes down to genetics, which influences how our brains process bitter-tasting and cold beverages.
What's more, it turns out that beer's bitter taste triggers evolutionary wiring designed to keep us away from potentially dangerous food and drink, and this trigger is stronger in some people than it is in others. [Is Booze Tasty or Bitter? Your Genes Decide]
But first, let's start with beer's bitter taste. As you may remember from science class, there are five types of taste cells within our taste buds that help us perceive salty, sweet, sour, umami (savory) and bitter flavors. Once the taste buds identify specific flavors, taste receptors send this data via nerves to the brain stem.
"If you think of a receptor as a lock, then whatever it binds to is a specific key," Dr. Virginia Utermohlen Lovelace, an associate professor emeritus of nutritional sciences at Cornell University in Ithaca, New York, told Live Science. "The cell to which that receptor is attached sends a message to the brain to say, 'Oooh this is bitter!'"
There are a whopping 25 different types of taste receptors for bitterness in the human body. In comparison, there are only two different kinds of salt receptors. Meanwhile, beer's bitterness largely comes from hops. The alpha and beta acids found in hops, as well as the low concentrations of ethanol in beer, bind to three of these 25 bitter receptors, signaling a strong bitter taste to the brain when you take a sip of lager, Lovelace said.
But what makes bitter flavors hard to swallow? The next time your friends delight in introducing you to a new craft IPA, you can tell them that their singular tastes are in direct opposition to evolutionary instinct. Humans actually evolved bitter taste receptors for our own safety — to identify poisonous foods that could be harmful.
"Bitter taste is considered a warning system for poisoning," researchers in a 2009 study published in the journal Chemosensory Perception concluded. "Many toxic compounds appear to taste bitter; yet, toxicity seems not to be directly correlated with the taste threshold concentrations of bitter compounds," the researchers said.
In other words, just because something tastes bitter and makes you wince, that doesn't automatically mean that beer (or any other bitter food or beverage) is out to kill you.
This brings us to the science behind genetic functional polymorphisms, also known as genetic variations. Since there are so many taste receptors for bitterness, it's safe to say that bitter flavors — how we perceive them and how much we can tolerate them — have a plethora of inheritable genetic possibilities.
According to a 2017 study published in the journal Scientific Reports, TAS2R16 alone (which is one of the 25 bitter receptors in the human body) has 17 polymorphisms, including a variant that is associated with alcohol dependence.
Lovelace explained that one of the easiest indicators of bitter sensitivity is the number of taste buds you have in your mouth. The more taste buds you have, the more likely you are to detest hoppy beers.
Bitter receptors, however, are not the only variants at play. The carbonation in beer turns on our "cold" receptors (the same temperature receptors that make minty gum taste cold and cinnamon taste hot). Cold receptors have genetic variations too, so while you may not be sensitive to the bitterness of beer, the receptors that signal coldness might also make beer seem unappealing, Lovelace said.
If you're sensitive to the bitterness in beer or other alcohol, there are countermeasures to help "drown out" the strength of the bitter receptors, she noted.
"Sweet and salty foods can help turn off the effects of the bitter receptors, which is why we have beer nuts and why we drink tequila with salt!" Lovelace said. "When you cut away the bitter, you're more likely to receive the specifics of the flavors underneath."
Original article on Live Science.