The Science Behind How We Taste

Everyone has a preference on taste, but why? Throw in a pinch of nature, a dash of nurture, and the senses of smell, sight, and sound, and that's the science behind taste.

From the WebMD Archives

Why does one person love blue cheese and another cringe at the thought? How can someone eat Brussels sprouts by the bunch and someone else prefer only peas? Taste, a sense that adds flavor to the world, is a complicated but oh-so-important part of life.

"The sense of taste is a sensory system like the eye," says Ilene Bernstein, PhD, a professor of psychology at the University of Washington. "The tongue is sensitive to different tastes -- sweet, sour, bitter, or salty. Taste as a sense is the perception of a combination of these chemical signals on the tongue."

While it sounds simple, taste involves so much more than these four simple categories that we learned about in grade school. From genes, to environment, to a fifth taste referred to as umami, experts explain to WebMD the science behind taste.

Nature and Nurture

Taste is a product of more than just buds on your tongue. It's a combination of how a food smells, looks, and sounds. When we eat celery, it has to crunch. When we drink coffee, we expect a certain aroma. And of course, how a person perceives taste also has to do with nature and nurture.

"Taste is a product of our genes and our environment," says Leslie J. Stein, PhD, from the Monell Chemical Senses Center in Philadelphia. "Our food preferences are determined by multiple factors, including genes, experience, and age."

Genes play a part by giving a person a predetermined taste preference, and our environment is a factor in learning new tastes.

"Recent research has demonstrated that our genes help to determine how we detect the basic tastes by influencing the configuration of taste receptors," says Stein. "Part of why you might like broccoli while your best friend finds it bitter is because you have different genes, which code for different bitter receptors."

Likewise, "Experience is also an important determinant of food preferences," says Stein. "For example, infants and young children need to learn what foods are safe to eat. Even before birth, information about specific flavors of mothers' diets passes to infants through amniotic fluid."

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Sweet or Salty?

Genetics and upbringing aside, it's not surprising that everyone has at least a little bit of a sweet tooth.

"I would say that as a species, almost everyone has some degree of a sweet preference," says Bernstein. "We are born having automatic positive responses to sweetness."

When it comes to salt preference, an unlikely factor plays a role.

"Salt has a lot of variability in terms of preference, and I don't think we know too much about it," says Bernstein. "But we did do this amazing study some years ago that found one factor that contributes to salt preference is whether or not a person's mother experienced severe to moderate morning sickness."

Bernstein, who co-authored the study, which was published in Appetite, says researchers found that the loss of electrolytes and sodium during morning sickness has an impact on the offspring's salt preference.

Training Your Taste

Training yourself to like something you despise seems odd, but whether it's lower salt intake or more fruit and vegetables, sometimes a person needs to eat foods that they may not be fond of. Unfortunately, it's not that easy.

"We can't change our genes, so some food likes or dislikes may be difficult to alter drastically," says Stein. "Repeated exposure can increase relative liking for a food but may not be able to change a disliked food into one that is liked. In other words, exposure may make a disliked food less disliked."

While repeat exposure to a food can decrease dislike, it can also increase liking. For instance, research done at the Monell Chemical Senses Center showed that people who stick to a lower-sodium diet over time eventually prefer lower levels of saltiness in their food, explains Stein.

And of course, there are acquired tastes, such as caviar.

"If you really hate something, having it over and over again may not change it," says Bernstein. "But we know people develop tastes for something -- in social settings you have to eat things you may not like but eventually, you acquire a taste for it."

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The 5th Taste

Sweet, salty, sour, bitter, and ... umami?

"Umami is the taste of glutamate, an amino acid found throughout the human body and in protein-containing foods," Stein tells WebMD. "Glutamate elicits a sensation, which is often described as brothy, full-bodied, meaty, and savory. This savory sensation has been termed umami in Japanese, which roughly translates into 'wonderful taste.'"

As a part of Japanese cuisine for more than 100 years, explains Stein, umami is now considered a component of taste around the world.

"To imagine savory taste, think of chicken broth, a ripe beefsteak tomato, or Parmesan cheese," says Stein. "Recent biochemical studies have revealed a separate taste receptor that can detect this amino acid, increasing the likelihood that umami is a separate and distinct taste sensation, which perhaps evolved to ensure adequate consumption of protein."

Flavor vs. Taste

Flavor and taste seem like the same thing, but hold your nose when you're eating and you'll quickly draw a distinction.

"Most people think that flavor is the same as taste, but that's not true," says Stein. "The distinctive flavor of most foods and drinks comes more from smell than it does from taste."

While sugar has a sweet taste, strawberry is a flavor. While coffee may be bitter, it's aroma is also all about flavor.

"An airway between the nose and mouth lets people combine aroma with the five basic tastes to enjoy thousands of flavors," says Stein.

Still not sure of the difference? Stein recommends the jellybean test.

"Take two red jellybeans of differing flavors, such as cherry and strawberry," Stein tells WebMD. "While holding your nose tightly closed, pop one of the jellybeans into your mouth and chew. Try to identify the flavor. You'll know that it's sweet but won't be able to determine whether it's cherry or strawberry until you let go of your nose and let the olfactory information whoosh up into your nose."

Flavor also includes texture, temperature, and irritation - such as with chile peppers.

"The spiciness of food is conveyed through a third sensory system known as chemical irritation," says Stein. "This system involves the trigeminal nerve, which has thousands of nerve endings located in the nose, mouth, throat, and eyes. The nerve endings sense and respond to the sting of ammonia, the coolness of menthol, and the burn of chili peppers or ginger."

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Taste Over Time

As we get older, our bodies slow down. So, too, do our taste buds.

"Our tastes buds have a very short life, and they turn over every few days," says Mary Ellen Camire, PhD, a professor in the department of Food Science & Human Nutrition at the University of Maine. "But that rate slows as you grow older, so your taste sharpness declines."

So if a person prefers a certain amount of salt on food, over time, he'll have to use more and more salt to get the desired taste as his taste buds slow in their regeneration process.

"Smell tends to decline with age, too," Camire tells WebMD. "Since smell is a very important part of food, as that declines so does the overall sense of taste."

The Supertaster

The sense of taste is powerful enough, but throw in supertasters, and you're at a whole new level of sensory perception.

"A supertaster is someone who has an enhanced genetic ability to detect bitterness," says Camire, who is also a food science communicator with the Institute of Food Technologists in Chicago. "People who have these genes pick up bitterness in addition to everything else. There's a lot of research going on around the role genetics play in taste; it's a contentious subject."

Who knew taste could be such a meaty subject?

WebMD Feature Reviewed by Brunilda Nazario, MD on May 16, 2005

Sources

SOURCES: Ilene Bernstein, PhD, professor of psychology, University of Washington. Bernstein, I. Appetite, 1998; vol 30: pp 297-307. Mary Ellen Camire, PhD, department of food science & human nutrition, University of Maine, Orono; food science communicator, Institute of Food Technologists, Chicago. Leslie J. Stein, PhD, Science Communications, Monell Chemical Senses Center, Philadelphia.

© 2005 WebMD, Inc. All rights reserved.

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