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.

‘Water’ in Kansas City Woman’s Ear Turned Out to Be a Venomous Brown Recluse Spider

N-sky/iStock via Getty Images
N-sky/iStock via Getty Images

Susie Torres, a resident of Kansas City, Missouri, woke up on Tuesday morning with the distinct feeling that water was lodged in her left ear. She likened it to the swooshing sensation that can often happen after swimming, WDAF-TV reports.

Instead of waiting for the problem to resolve itself, Torres went to the doctor—a decision that might have saved her from some serious pain. The medical assistant was the first to realize something was alarmingly amiss, and immediately called for backup.

“She ran out and said ‘I’m going to get a couple more people,’” Torres told 41 Action News. “She then said, ‘I think you have an insect in there.’” For many people, the thought of having any live insect stuck in an ear would be enough to cue a small- or large-scale freak-out, but Torres stayed calm.

The doctors “had a few tools and worked their magic and got it out,” Torres said. The “it” in question turned out to be a spider—and not just any harmless house spider (which you shouldn’t kill, by the way). It was a venomous brown recluse spider.

“Gross,” Torres told WDAF-TV. “Why, where, what, and how.”

Miraculously, the spider didn’t bite Torres. If it had, she would’ve ended up visiting the doctor with more than general ear discomfort: Brown recluse bites can cause pain, burning, fever, nausea, and purple or blue discoloration of the surrounding skin, according to Healthline.

Torres may have remained admirably level-headed throughout the ordeal, but that doesn’t mean she’s taking it lightly. “I went and put some cotton balls in my ears last night,” she told WDAF-TV. “I’m shaking off my clothes, and I don’t put my purse on the floor. I’m a little more cautious.”

Is this the first time an insect has posted up in the ear of an unsuspecting, innocent human? Absolutely not—here are six more horror stories, featuring a cockroach, a bed bug, and more.

[h/t WDAF-TV]

12 Fantastic Facts About the Immune System

monkeybusinessimages/iStock via Getty Images
monkeybusinessimages/iStock via Getty Images

If it weren't for our immune system, none of us would live very long. Not only does the immune system protect us from external pathogens like viruses, bacteria, and parasites, but it also battles cells that have mutated due to illnesses, like cancer, within the body. Here are 12 fascinating facts about the immune system.

1. The immune system saves lives.

The immune system is a complex network of tissues and organs that spreads throughout the entire body. In a nutshell, it works like this: A series of "sensors" within the system detects an intruding pathogen, like bacteria or a virus. Then the sensors signal other parts of the system to kill the pathogen and eliminate the infection.

"The immune system is being bombarded by all sorts of microbes all the time," Russell Vance, professor of immunology at University of California, Berkeley and an investigator for the Howard Hughes Medical Institute, tells Mental Floss. "Yet, even though we're not aware of it, it's saving our lives every day, and doing a remarkably good job of it."

2. Before scientists understood the immune system, illness was chalked up to unbalanced humors.

Long before physicians realized how invisible pathogens interacted with the body's system for fighting them off, doctors diagnosed all ills of the body and the mind according to the balance of "four humors": melancholic, phlegmatic, choleric, or sanguine. These criteria, devised by the Greek philosopher Hippocrates, were divided between the four elements, which were linked to bodily fluids (a.k.a. humors): earth (black bile), air (blood), water (phlegm) and fire (yellow bile), which also carried properties of cold, hot, moist, or dry. Through a combination of guesswork and observation, physicians would diagnose patients' humors and prescribe treatment that most likely did little to support the immune system's ability to resist infection.

3. Two men who unraveled the immune system's functions were bitter rivals.

Two scientists who discovered key functions of the immune system, Louis Pasteur and Robert Koch, should have been able to see their work as complementary, but they wound up rivals. Pasteur, a French microbiologist, was famous for his experiments demonstrating the mechanism of vaccines using weakened versions of the microbes. Koch, a German physician, established four essential conditions under which pathogenic bacteria can infect hosts, and used them to identify the Mycobacterium tuberculosis bacterium that causes tuberculosis. Though both helped establish the germ theory of disease—one of the foundations of modern medicine today—Pasteur and Koch's feud may have been aggravated by nationalism, a language barrier, criticisms of each other's work, and possibly a hint of jealousy.

4. Specialized blood cells are the immune system's greatest weapon.

The most powerful weapons in your immune system's arsenal are white blood cells, divided into two main types: lymphocytes, which create antigens for specific pathogens and kill them or escort them out of the body; and phagocytes, which ingest harmful bacteria. White blood cells not only attack foreign pathogens, but recognize these interlopers the next time they meet them and respond more quickly. Many of these immune cells are produced in your bone marrow but also in the spleen, lymph nodes, and thymus, and are stored in some of these tissues and other areas of the body. In the lymph nodes, which are located throughout your body but most noticeably in your armpits, throat, and groin, lymphatic fluid containing white blood cells flows through vein-like tubules to escort foreign invaders out.

5. The spleen helps your immune system work.

Though you can live without the spleen, an organ that lies between stomach and diaphragm, it's better to hang onto it for your immune function. According to Adriana Medina, a doctor who specializes in hematology and oncology at the Alvin and Lois Lapidus Cancer Institute at Sinai Hospital in Baltimore, your spleen is "one big lymph node" that makes new white blood cells and cleans out old blood cells from the body.

It's also a place where immune cells congregate. "Because the immune cells are spread out through the body," Vance says, "eventually they need to communicate with each other." They do so in both the spleen and lymph nodes.

6. You have immune cells in all of your tissues.

While immune cells may congregate more in lymph nodes than elsewhere, "every tissue in your body has immune cells stationed in it or circulating through it, constantly roving for signs of attack," Vance explains. These cells also circulate through the blood. The reason for their widespread presence is that there are thousands of different pathogens that might infect us, from bacteria to viruses to parasites. "To eliminate each of those different kinds of threats requires specialized detectors," he says.

7. How friendly you're feeling could be linked to your immune system.

From an evolutionary perspective, humans' high sociability may have less to do with our bigger brains, and more to do with our immune system's exposure to a greater number of bacteria and other pathogens.

Researchers at the University of Virginia School of Medicine have theorized that interferon gamma (IG), a substance that helps the immune system fight invaders, was linked to social behavior, which is one of the ways we become exposed to pathogens.

In mice, they found IG acted as a kind of brake to the brain's prefrontal cortex, essentially stopping aberrant hyperactivity that can cause negative changes in social behavior. When they blocked the IG molecule, the mice's prefrontal cortexes became hyperactive, resulting in less sociability. When they restored the function, the mice's brains returned to normal, as did their social behavior.

8. Your immune system might recruit unlikely organs, like the appendix, into service.

The appendix gets a bad rap as a vestigial organ that does nothing but occasionally go septic and create a need for immediate surgery. But the appendix may help keep your gut in good shape. According to Gabrielle Belz, professor of molecular immunology at the Walter and Eliza Hall Institute of Medical Research in Melbourne, Australia, research by Duke University's Randal Bollinger and Bill Parker suggests the appendix houses symbiotic bacteria that are important for overall gut health—especially after infections wipe out the gut's good microbes. Special immune cells known as innate lymphoid cells (ILCs) in the appendix may help to repopulate the gut with healthy bacteria and put the gut back on track to recovery.

9. Gut bacteria has been shown to boost immune systems in mice.

Researchers at the University of Chicago noticed that one group of mice in their lab had a stronger response to a cancer treatment than other mice. They eventually traced the reason to a strain of bacteria—Bifidobacterium—in the mice's guts that boosted the animals' immune system to such a degree they could compare it to anti-cancer drugs called checkpoint inhibitors, which keep the immune system from overreacting.

To test their theory, they transferred fecal matter from the robust mice to the stomachs of less immune-strengthened mice, with positive results: The treated mice mounted stronger immune responses and tumor growth slowed. When they compared the bacterial transfer effects with the effects of a checkpoint inhibitor drug, they found that the bacteria treatment was just as effective. The researchers believe that, with further study, the same effect could be seen in human cancer patients.

10. Scientists are trying to harness the immune system's "Pac-Man" cells to treat cancer.

Aggressive pediatric tumors are difficult to treat due to the toxicity of chemotherapy, but some researchers are hoping to develop effective treatments without the harmful side effects. Stanford researchers designed a study around a recently discovered molecule known as CD47, a protein expressed on the surface of all cells, and how it interacts with macrophages, white blood cells that kill abnormal cells. "Think of the macrophages as the Pac-Man of the immune system," Samuel Cheshier, lead study author and assistant professor of neurosurgery at Stanford Medicine, tells Mental Floss.

CD47 sends the immune system's macrophages a "don't eat me" signal. Cancer cells fool the immune system into not destroying them by secreting high amounts of CD47. When Cheshier and his team blocked the CD47 signals on cancer cells, the macrophages could identify the cancer cells and eat them, without toxic side effects to healthy cells. The treatment successfully shrank all five of the common pediatric tumors, without the nasty side effects of chemotherapy.

11. A new therapy for type 1 diabetes tricks the immune system.

In those with type 1 diabetes, the body attacks its own pancreatic cells, interrupting its normal ability to produce insulin in response to glucose. In a 2016 paper, researchers at MIT, in collaboration with Boston's Children's Hospital, successfully designed a new material that allows them to encapsulate and transplant healthy pancreatic "islet" cells into diabetic mice without triggering an immune response. Made from seaweed, the substance is benign enough that the body doesn't react to it, and porous enough to allow the islet cells to be placed in the abdomen of mice, where they restore the pancreatic function. Senior author Daniel Anderson, an associate professor at MIT, said in a statement that this approach "has the potential to provide [human] diabetics with a new pancreas that is protected from the immune system, which would allow them to control their blood sugar without taking drugs. That's the dream."

12. Immunotherapy is on the cutting edge of immune system research.

Over the last few years, research in the field of immunology has focused on developing cancer treatments using immunotherapy. This method engineers the patient's own normal cells to attack the cancer cells. Vance says the technique could be used for many more conditions. "I feel like that could be just the tip of the iceberg," he says. "If we can understand better what the cancer and immunotherapy is showing, maybe we can go in there and manipulate the immune responses and get good outcomes for other diseases, too."

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