12 Facts About the Sense of Taste

iStock/m-imagephotography
iStock/m-imagephotography

A lot more than your tongue is involved in the process of tasting food. Taste is not only one of the most pleasurable of the five senses, but a surprisingly complex sense that science is beginning to understand—and manipulate. Here are 12 fascinating facts about your ability to taste.

1. Everyone has a different number of taste buds.

We all have several thousand taste buds in our mouths, but the number varies from person to person. The average range is between 2000 and 10,000. And taste buds are not limited to your tongue; They can be found in the roof and walls of your mouth, throat, and esophagus. As you age, your taste buds become less sensitive, which experts believe may be why foods that you don’t like as a child become palatable to you as an adult.

2. You taste with your brain.

The moment you bite into a slice of pie, your mouth seems full of flavor. But most of that taste sensation is happening in your brain. More accurately, cranial nerves and taste bud receptors in your mouth send molecules of your food to olfactory nerve endings in the roof of your nose. The molecules bind to these nerve endings, which then signal the olfactory bulb to send smell messages directly to two important cranial nerves, the facial nerve and the glossopharyngeal nerve, which communicate with a part of the brain known as the gustatory cortex.

As taste and nerve messages move further through the brain, they join up with smell messages to give the sensation of flavor, which feels as if it comes from the mouth.

3. You can’t taste well if you can’t smell.

When you smell something through your nostrils, the brain registers these sensations as coming from the nose, while smells perceived through the back of the throat activate parts of the brain associated with signals from the mouth. Since much of taste is odor traveling to olfactory receptors in your brain, it makes sense that you won’t taste much at all if you can’t smell. If you are unable to smell for reasons that include head colds, smoking cigarettes, side effects of medications, or a broken nose, olfactory receptors may either be too damaged, blocked, or inflamed to send their signals on up to your brain.

4. Eating sweet foods helps form a memory of a meal.

Eating sweet foods causes your brain to remember the meal, according to a 2015 study in the journal Hippocampus, and researchers believe it can actually help you control eating behavior. Neurons in the dorsal hippocampus, the part of the brain central to episodic memory, are activated when you eat sweets. Episodic memory is that kind that helps you recall what you experienced at a particular time and place. "We think that episodic memory can be used to control eating behavior," said study co-author Marise Parent, of the Neuroscience Institute at Georgia State. "We make decisions like 'I probably won't eat now. I had a big breakfast.' We make decisions based on our memory of what and when we ate."

5. Scientists can turn tastes on and off by manipulating brain cells.

Dedicated taste receptors in the brain have been found for each of the five basic tastes: sweet, sour, salty, bitter, and umami (savory). In 2015, scientists outlined in the journal Nature how they were able to turn specific tastes on or off in mice, without introducing food, by stimulating and silencing neurons in the brains. For instance, when they stimulated neurons associated with “bitter,” mice made puckering expressions, and could still taste sweet, and vice versa.

6. You can tweak your taste buds.

Most of us have had the experience of drinking perfectly good orange juice after brushing our teeth, only to have it taste more like unsweetened lemon juice. Taste buds, it turns out, are sensitive enough that certain compounds in foods and medicines can alter our ability to perceive one of the five common tastes. The foaming agent sodium lauryl/laureth sulfate in most toothpaste seems to temporarily suppress sweetness receptors. This isn't so unusual. A compound called cynarin in artichokes temporarily blocks your sweet receptors. Then, when you drink water, the cynarin is washed away, making your sweet receptors “wake up” so the water tastes sweet. A compound called miraculin, found in the herb Gymnema sylvestre, toys with your sweet receptors in a similar way.

7. The smell of ham can make your food “taste” saltier.

There’s an entire industry that concocts the tastes of the food you buy at the grocery store. Working with phenomena known as phantom aromas or aroma-taste interactions, scientists found that people associate “ham” with salt. So simply adding a subtle ham-like scent or flavor to a food can make your brain perceive it as saltier than it actually is. The same concept applies to the scent of vanilla, which people perceive as sweet.

8. Your taste buds prefer savory when you fly.

A study by Cornell University food scientists found that loud, noisy environments, such as when you’re traveling on an airplane, compromise your sense of taste. The study found that people traveling on airplanes had suppressed sweet receptors and enhanced umami receptors. The German airline Lufthansa confirmed that on flights, passengers ordered nearly as much tomato juice as beer. The study opens the door to new questions about how taste is influenced by more than our own internal circuitry, including our interactions with our environments.

9. Picky eaters may be “supertasters.”

If you’re a picky eater, you may have a new excuse for your extreme dislike of eggplant or sensitivity to the slightest hint of onion. You might be a supertaster—one of 25 percent of people who have extra papillae in your tongue. That means you have a greater number of taste buds, and thus more specific taste receptors.

10. Some of your taste preferences are genetic.

While genetics may not fully explain your love of the KFC Double Down or lobster ice cream, there may be code written into your DNA that accounts for your preference for sweet foods or your aversion to certain flavors. The first discovery of a genetic underpinning to taste came in 1931, when chemist Arthur Fox was working with powdered PTC (phenylthiocarbamide), and some of the compound blew into the air. One colleague found it to have a bitter taste, while Fox did not perceive that. They conducted an experiment among friends and family and found wide variation in how (and whether) people perceived the flavor of the PTC to be bitter or tasteless. Geneticists later discovered that the perception of PTC flavor (similar to naturally occurring compounds) is based in a single gene, TAS2R38, that codes for a taste receptor on the tongue. In a 2005 study, researchers at the Monell Chemical Senses Center found that the version of this gene also predicted a child's preference for sweet foods.

11. Your genes influence whether you think cilantro tastes like soap.

There may be no flavor more hotly debated or deeply loathed than the herb cilantro (also known as coriander). Entire websites, like IHateCilantro.com, complain about its “soapy” or “perfumy” flavor, while those who like it simply think it gives a nice kick to their salsa. Researchers at the consumer genetics company 23andMe identified two common genetic variants linked to people's “soap” perceptions. A follow-up study in a separate subset of customers confirmed the associations. The most compelling variant can be found within a cluster of olfactory receptor genes, which influence our sense of smell. One of those genes, OR6A2, encodes a receptor that is highly sensitive to aldehyde chemicals, which cilantro contains.

12. Sugar cravings have a biological basis.

Your urge for more hot fudge may have little to do with a lack of self-control. Scientists think that our yearning for sweets is a biological preference that may have been designed to ensure our survival. The liking for sweet tastes in our ancient evolution may have ensured the acceptance of sweet-tasting foods, such as breast milk and vitamin-rich fruits. Moreover, recent research suggests that we crave sweets for their pain-reducing properties.

7 Facts About Blood

Moussa81/iStock via Getty Images
Moussa81/iStock via Getty Images

Everyone knows that when you get cut, you bleed—a result of the constant movement of blood through our bodies. But do you know all of the functions the circulatory system actually performs? Here are some surprising facts about human blood—and a few cringe-worthy theories that preceded the modern scientific understanding of this vital fluid.

1. Doctors still use bloodletting and leeches to treat diseases.

Ancient peoples knew the circulatory system was important to overall health. That may be one reason for bloodletting, the practice of cutting people to “cure” everything from cancer to infections to mental illness. For the better part of two millennia, it persisted as one of the most common medical procedures.

Hippocrates believed that illness was caused by an imbalance of four “humors”—blood, phlegm, black bile, and yellow bile. For centuries, doctors believed balance could be restored by removing excess blood, often by bloodletting or leeches. It didn’t always go so well. George Washington, for example, died soon after his physician treated a sore throat with bloodletting and a series of other agonizing procedures.

By the mid-19th century, bloodletting was on its way out, but it hasn’t completely disappeared. Bloodletting is an effective treatment for some rare conditions like hemochromatosis, a hereditary condition causing your body to absorb too much iron.

Leeches have also made a comeback in medicine. We now know that leech saliva contains substances with anti-inflammatory, antibiotic, and anesthetic properties. It also contains hirudin, an enzyme that prevents clotting. It lets more oxygenated blood into the wound, reducing swelling and helping to rebuild tiny blood vessels so that it can heal faster. That’s why leeches are still sometimes used in treating certain circulatory diseases, arthritis, and skin grafting, and helps reattach fingers and toes. (Contrary to popular belief, even the blood-sucking variety of leech is not all that interested in human blood.)

2. Scientists didn't understand how blood circulation worked until the 17th century.

William Harvey, an English physician, is generally credited with discovering and demonstrating the mechanics of circulation, though his work developed out of the cumulative body of research on the subject over centuries.

The prevailing theory in Harvey’s time was that the lungs, not the heart, moved blood through the body. In part by dissecting living animals and studying their still-beating hearts, Harvey was able to describe how the heart pumped blood through the body and how blood returned to the heart. He also showed how valves in veins helped control the flow of blood through the body. Harvey was ridiculed by many of his contemporaries, but his theories were ultimately vindicated.

3. Blood types were discovered in the early 20th century.

Austrian physician Karl Landsteiner discovered different blood groups in 1901, after he noticed that blood mixed from people with different types would clot. His subsequent research classified types A, B and O. (Later research identified an additional type, AB). Blood types are differentiated by the kinds of antigens—molecules that provoke an immune system reaction—that attach to red blood cells.

People with Type A blood have only A antigens attached to their red cells but have B antigens in their plasma. In those with Type B blood, the location of the antigens is reversed. Type O blood has neither A nor B antigens on red cells, but both are present in the plasma. And finally, Type AB has both A and B antigens on red cells but neither in plasma. But wait, there’s more! When a third antigen, called the Rh factor, is present, the blood type is classified as positive. When Rh factor is absent, the blood type is negative.

Scientists still don’t understand why humans have different blood types, but knowing yours is important: Some people have life-threatening reactions if they receive a blood type during a transfusion that doesn’t “mix” with their own. Before researchers developed reliable ways to detect blood types, that tended to turn out badly for people receiving an incompatible human (or animal!) blood transfusion.

4. Blood makes up about 8 percent of our total body weight.

Adult bodies contain about 5 liters (5.3 quarts) of blood. An exception is pregnant women, whose bodies can produce about 50 percent more blood to nourish a fetus.)

Plasma, the liquid portion of blood, accounts for about 3 liters. It carries red and white blood cells and platelets, which deliver oxygen to our cells, fight disease, and repair damaged vessels. These cells are joined by electrolytes, antibodies, vitamins, proteins, and other nutrients required to maintain all the other cells in the body.

5. A healthy red blood cell lasts for roughly 120 days.

Red blood cells contain an important protein called hemoglobin that delivers oxygen to all the other cells in our bodies. It also carries carbon dioxide from those cells back to the lungs.

Red blood cells are produced in bone marrow, but not everyone produces healthy ones. People with sickle cell anemia, a hereditary condition, develop malformed red blood cells that get stuck in blood vessels. These blood cells last about 10 to 20 days, which leads to a chronic shortage of red blood cells, often causing to pain, infection, and organ damage.

6. Blood might play a role in treating Alzheimer's disease.

In 2014, research led by Stanford University scientists found that injecting the plasma of young mice into older mice improved memory and learning. Their findings follow years of experiments in which scientists surgically joined the circulatory systems of old and young mice to test whether young blood could reverse signs of aging. Those results showed rejuvenating effects of a particular blood protein on the organs of older mice.

The Stanford team’s findings that young blood had positive effects on mouse memory and learning sparked intense interest in whether it could eventually lead to new treatments for Alzheimer’s disease and other age-related conditions.

7. The sight of blood can make people faint.

For 3 to 4 percent of people, squeamishness associated with blood, injury, or invasive medical procedures like injections rises to the level of a true phobia called blood injury injection phobia (BII). And most sufferers share a common reaction: fainting.

Most phobias cause an increase in heart rate and blood pressure, and often muscle tension, shakes, and sweating: part of the body’s sympathetic nervous system’s “fight or flight” response. But sufferers of BII experience an added symptom. After initially increasing, their blood pressure and heart rate will abruptly drop.

This reaction is caused by the vagus nerve, which works to keep a steady heart rate, among other things. But the vagus nerve sometimes overdoes it, pushing blood pressure and heart rate too low. (You may have experienced this phenomenon if you’ve ever felt faint while hungry, dehydrated, startled, or standing up too fast.) For people with BII, the vasovagal response can happen at the mere sight or suggestion of blood, needles, or bodily injury, making even a routine medical or dental checkup cause for dread and embarrassment.

What Purpose Does the Belly Button Serve?

misuma/iStock via Getty Images
misuma/iStock via Getty Images

While your eyelashes are protecting your eyes, your lungs are letting you breathe, and virtually every other part of your body—inside and out—is performing its own relatively well-known task, your belly button is just sitting there collecting lint. And while it’s true that your navel served its most important purpose before you were born, it’s not totally useless now.

According to ZME Science, back when you were a fetus, your belly button was more of a belly portal: Your umbilical cord extended from it and connected you to the placenta on your mother’s uterine wall. That way, the placenta could channel nutrients and oxygen to you through the cord, and you could send back waste.

Your umbilical cord was cut when you were born, creating a tiny bulge that left behind some scar tissue after it healed. That scar tissue is your belly button, navel, or umbilicus. Though you may have heard that the shape of your belly button is a direct result of the scissor skills of the doctor who delivered you, that’s not true. Dr. Dan Polk, a neonatologist in the Chicago area, told the Chicago Tribune that a belly button's shape “has to do with how much baby skin leads onto the umbilical cord from the baby’s body. Less skin makes an innie; more skin makes an outie.” About 90 percent of people have innies.

Regardless of how your belly button looks, you probably don’t use it on a daily basis. However, if you’ve studied anatomy, medicine, or a related field, you might recognize it as the central point by which the abdomen is divided into the following quadrants: right upper, left upper, right lower, and left lower. Another way of classifying that area is into nine regions—including the hypochondriac, lumbar, iliac, epigastric, and hypogastric regions—with the umbilical region at the very center.

Abdominopelvic regions diagram
Blausen Medical, Wikimedia Commons // CC BY 3.0

Your belly button can also serve as the opening for laparoscopic surgery, which can save you from having a scar elsewhere on your abdomen.

The navel is a great central landmark outside of medicine, too. If you’ve taken yoga or Pilates classes, you may have heard it referred to as the center of balance or center of gravity. Because it sits right on top of your abdominal muscles, your belly button is an easy marker for your instructor to mention when they want you to access your core, which helps you balance.

And, of course, belly buttons are notorious for storing quite a bit of lint, which always seems to be blue (you can learn more about that here).

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