A Matter of Taste

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GENETICS, culture, personal experience and sometimes nutritional needs can affect strong taste preferences—for cilantro and beer; vanilla, licorice and cinnamon; turnips and watercress; sugar and salt. But sufficient motivation can change intense dislike, which also generally diminishes with age.

“Every new experience causes the brain to update and enlarge its set of patterns, and this can lead to a shift in how we perceive a food,” according to Northwestern University neuroscientist Jay Gottfried, who studies how the brain perceives smells.

Taste buds containing receptors for the five basic tastes—sweet, sour, salty, bitter and umami (from glutamate, in broth, etc.)—are distributed in small bumps called papillae throughout the tongue, roof of the mouth, and throat. They number around 10,000 at birth and start to decrease after age 50.

Ethnic Europeans have fewer taste buds, while in some parts of Asia, South America and Africa, 85% of native populations are “highly sensitive” or “supertasters.”

Unborn and breastfed babies “taste what their mothers eat…and have been shown to develop early affinities to certain flavours in their mothers’ diets,” according to The Guardian.  Learning plays a role in taste. Vanilla in the West is associated with sweet foods and is used to enhance the perception of sweetness (adding vanilla is a low-calorie way to sweeten plain yogurt).  But in East Asia where vanilla is used in savory dishes, it doesn’t taste sweet.

While European cuisine combines similar flavors, Asian cooking does the opposite. And Europeans generally dislike cinnamon, turning up their noses at carrot cake and fleeing from the aroma in U.S. coffee shops. For licorice, the search is still on for why it’s widely disliked, although this seems to be something people are born with. Meanwhile, too much black licorice can cause high blood pressure and heart disease.

Senses of smell and taste evolved to evoke strong emotions because they were critical to finding food and mates and avoiding predators…so when “a flavor fits into a pattern that involves chemical cleaning agents and dirt or crawly insects,” we avoid it, Gottfried explains.  For some, cilantro’s odor suggests soap and/or stink bugs.

Bitterness is the taste linked to the greatest number of genes and thus to the greatest variation in preferences. Although only two genes affect how we perceive sweetness and two affect umami, at least 25 and maybe 40 affect bitterness, explains Nicole Garneau, director of the Genetics of Taste Lab at the Denver Museum of Nature and Science.

For the 25% of the population who can’t taste bitterness, genes change the shape of bitterness taste receptors to prevent binding with bitter food molecules. Among the 75% who can detect bitterness, different combinations of genes lead some to like grapefruit but not kale, quinine but not coffee, or “hoppy beer” ( bitterness comes from hops).

“Flavor consequence” and “conditioned taste aversion” refer to the effects of experience on taste and help explain how bitter beer, including especially bitter IPAs, have become popular.  “Hardly anyone likes bitter beer the first time they try it,” says John Hayes, director of the Sensory Evaluation Center at Penn State. But if they get “positive post-ingestion consequences like having a good time with friends,” they might keep trying it and like it more with every pint.

The discovery of a genetic link to bitter perception began in the 1930s with a chemical compound known as PTC. That led to subsequent research on individual reactions to similar compounds in foods—for example, turnips and watercress, which are more appealing to genetically insensitive people than to people who find them bitter.

Bitterness also plays a role in the taste of cilantro—the most famously disliked herb—which has an especially vocal group and its own website “I Hate Cilantro.” This distaste was first traced to a group of olfactory-receptor genes that pick up on the smell of aldehyde chemicals that are found in cilantro, as well as in soap and stink bugs.

In twin studies, identical twins are more similar in their reaction to bitterness than fraternal twins.  Questioning 527 sets of twins about cilantro, scientists at the Monnell Chemical Senses Center in Philadelphia found three more genes that play a role: two for tasting bitter foods, and one that detects pungent compounds like those in wasabi.

Cilantro preference, however, has “only a small underlying genetic component,” according to California-based geneticist Nicholas Eriksson. To build an appreciation for the herb, the common suggestion is to start with cilantro pesto, because crushing the leaves releases enzymes that convert the soapy compounds into more mild aromas.

Gottfried, a “former cilantrophobe,” found that after eating “all kinds of things” and experiencing pleasure from sharing with friends: “It can still remind me of soap but that association fades into the background.”

Liking sugar can also be linked to the bitterness gene: those with one or two copies of the gene were more likely to favor foods and beverages with high sugar content. Conversely, those who don’t care much for sweets could be supertasters, who have inherited a greater number of taste buds and thus taste all flavors more intensely.“These people tend to shun strong-flavored foods including rich deserts…and may explain why supertasters are more likely to be slim,” according to Smithsonian magazine.

Craving sugar and fat can also be linked to mood.  Carbohydrate consumption increases the release of the neurotransmitter serotonin, which plays a role in mood control: depression can increase a craving for carbohydrates in an effort to feel better.  On the other hand, eating protein can help stabilize blood sugar levels to offset sugar cravings.

Salt craving may be influenced by dehydration or related to the “stress hormone” cortisol. Because stress prompts lower levels of cortisol in people with higher sodium levels, craving salt could be a way the body copes with stress.  Cortisol depletion with Addison’s disease is another cause of salt craving.

Some physical disorders can also cause bad tastes. For example, in phantom taste perception, sufferers experience a lingering unpleasant taste after swallowing food. In the case of dysgeusia, bad tastes —foul, salty, rancid or metallic—persist in the mouth, often accompanied by “burning mouth syndrome.”  Most often linked to a diminished ability to smell, hypogeusia is a reduced ability to taste. Ageusia is the inability to detect taste, although true taste loss is rare.

Beer is the most common target of personal efforts to change taste perception, which requires motivation—especially for IPAs.   For cilantro, however, “Julia Child, an avowed cilantro hater, said she would just pick it out and throw it on the floor.”

—Mary Carpenter

Every Tuesday in this space, well-being editor Mary Carpenter reports on health news that affects our daily lives.