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12 Delectable Facts About the Science of Taste

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Now that the holiday season is over, you may be cutting back on indulgent meals because of your waistline. But your taste buds are eager for flavor year-round. A lot more than your tongue is involved in the process of tasting food. Taste is not only one of the most pleasurable of all the 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; between 2000 and 10,000 is the average range. 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 the brain to form a memory of a meal, according to a new 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 ACTIVATING AND SILENCING CLUSTERS OF 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).  Recently, 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 unfortunate, mouth-puckering 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” and thus making the water taste sweet. A compound called miraculin, found in the Indian 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 subtle 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 FLYING.

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.”

The picky eater may have a new excuse to turn down your homecooked meal: An extreme dislike of eggplant or sensitivity to the slightest hint of onion may mean you are a supertaster—one of 25 percent of people who have extra papillae in your tongue, in essence, a greater number of taste buds, thus receptors. 

10. SOME OF YOUR TASTE PREFERENCES ARE GENETIC.

While your genetics may not explain your love of peanut butter and mayonnaise sandwiches or rocky road ice cream specifically, 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 a chemist named 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 this. 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. IN FACT, YOUR GENES INFLUENCE WHETHER CILANTRO TASTES LIKE AN HERB OR LIKE SOAP.

There may be no flavor more hotly debated or deeply loathed than the humble cilantro herb (also known as coriander). Entire websites such as IHateCilantro.com exist extolling dislike for the herb’s “soapy” or “perfumy” flavor, while those who like it simply think it gives a nice kick to their salsa. Researchers at the consumer genetics firm 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 believe 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

All images courtesy of iStock 

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The Body
11 Interesting Facts About Lymph Nodes

The human body is an amazing thing. For each one of us, it's the most intimate object we know. And yet most of us don't know enough about it: its features, functions, quirks, and mysteries. Our series The Body explores human anatomy, part by part. Think of it as a mini digital encyclopedia with a dose of wow.

The lymphatic system is a crucial part of your body's ability to fight off infection and viruses. It's a key player in the immune system that functions by circulating lymphatic fluid through a series of lymph vessels all throughout your body. This fluid gathers up anything foreign, such as viruses and bacteria from your body tissues and flushes them to your lymph nodes, where immune cells attack whatever isn't helping your body. 

Mental Floss spoke to Adriana Medina, an internal medicine doctor with a specialty in hematology and oncology at the Alvin and Lois Lapidus Cancer Institute at Sinai Hospital in Baltimore, Maryland, about these important tissues. 

1. THERE ARE HUNDREDS OF NODES.

They're about size and shape of a pea, and hundreds of them are scattered all throughout the body. In order to fight many little pathogens and clear out unhelpful debris, your body needs a lot of nodes to rally to these causes, according to Medina. 

2. LYMPH NODES ARE HOME TO IMPORTANT IMMUNE CELLS.

"The lymph nodes are in charge of harboring lymphocytes," says Medina. Your body makes two main types of these immune cells, B-lymphocytes and T-lymphocytes (or B- and T-cells), which are crucial to your body's ability to fight off infections of all kinds. There are many sub-classes of the T-cells because "they are very important to attack infection," says Medina.

3. LYMPHOCYTES ESCORT FOREIGN INVADERS OUT.

When your lymph nodes receive some sort of foreign debris they recognize isn't ours, Medina says, "the B-lymphocytes are in charge of making antibodies." These antibodies "leave with the toxic substance," and signal other immune cells to come in and attack the cells.

4. WHERE DO ALL THE TOXINS GO?

Once the lymphatic fluid has grabbed up its targets, most of it returns to your blood stream, Medina explains, which is why it's so important for lymph cells to do their job: kill what aims to harm you before it gets flushed back into your system.

5. THERE ARE MANY CAUSES OF SWOLLEN LYMPH NODES.

When your immune system senses a foreign invader, be it a virus, bacteria, vaccine, or even some medications, it preps the lymph nodes to make antibodies and lymphocytes to fight off the offender. This also increases the amount of lymphatic fluid in the node, which can make it swollen and tender. Most of the time swollen lymph nodes are not a big cause for concern.

6. A HARD, RUBBERY LYMPH NODE IS A PROBLEM.

A lymph node that is harder rather than soft and persists for several weeks is worth a doctor visit. While lymph nodes can be tender or swollen and mobile when infected, "when there is a [cancerous] malignance…they're hard, rubbery, they don't move, and they don't go away. The lymph nodes are always telling us something."

7. YOU ARE THE PUMP FOR YOUR LYMPHATIC SYSTEM.

Unlike your blood, which has the heart to pump it through your body, your lymphatic fluid doesn't have a pump. Instead, it relies upon gravity and pressure, which you create when you move around, as well as light massage.

8. WHERE YOU FIND VEINS, YOU FIND LYMPHATIC VESSELS.

The lymphatic system and the circulatory system are separate systems, but connected, running in tandem like underground networks of streams. "Lymphatic vessels are distributed along the body wherever we have arteries [or] veins," says Medina.

9. YOUR LYMPH NODES AND YOUR SPLEEN WORK TOGETHER.

"The spleen is like one big lymph node," Medina says of the organ that lives between your stomach and diaphragm. "The spleen is able to produce additional blood cells in case we need it to." Additionally, she explains, many toxic substances are filtrated through the spleen. However, if something happens to your spleen and it needs to be removed, you can live without it; you just may become more prone to infection and require more vaccinations to protect you against aggressive viruses.

10. STAGES OF CANCER ARE DETERMINED BY THE NUMBER OF AFFECTED LYMPH NODES.

The easiest cancers to treat are those that remain in the tissue where they first occur. However, in metastatic cancers, cancer cells migrate to the lymph nodes, which can cause cancer to spread. "When the cancer is detected in lymph nodes, we have to try to find out how many lymph nodes are involved," Medina says. "Lymph node involvements [determines] the prognosis of the cancer." When lymph node involvement occurs, "the treatment has to be more aggressive," she says, often adding radiation to a regime of chemotherapy and other drugs.

11. RESEARCHERS ARE TURNING THE BODY'S OWN LYMPHOCYTES INTO CANCER FIGHTING TREATMENTS.

Breakthroughs in immunotherapy known as Car T-cell therapy turn the body's own immune system into a weapon against cancer by engineering patients' own immune cells to recognize and attack their tumors, according to the National Cancer Institute. "What's happening—it's just beautiful—is that [researchers] are using B-lymphocytes to fight not only breast cancer, but leukemia and lymphomas," Medina explains. "The results are so good and encouraging, changing chances of survival."

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The Body
13 Intriguing Facts About the Sciatic Nerve

The human body is an amazing thing. For each one of us, it's the most intimate object we know. And yet most of us don't know enough about it: its features, functions, quirks, and mysteries. Our series The Body explores human anatomy, part by part. Think of it as a mini digital encyclopedia with a dose of wow.

If you say someone's getting on your nerves, you could just cut to the chase and say they're getting on your sciatic nerve—this nerve is plenty big enough for both minor and major irritations. It's the largest nerve in the body, running a lengthy route from each side of your lower spine, deep into your buttock, wrapping around to the back of the thigh and into the foot. Mental Floss spoke to Loren Fishman, medical director of Manhattan Physical Medicine and Rehabilitation in NYC and associate clinical professor at Columbia Medical School. Here are 13 things we learned about this important part of the nervous system.

1. AT ITS LARGEST POINT, IT'S ABOUT AS BIG AROUND AS A MAN'S THUMB.

No wonder this nerve hurts when it gets irritated—at its biggest point, it's one heck of a large nerve, says Fishman. 

2. THE SCIATIC NERVE IS ACTUALLY MADE UP OF FIVE NERVES.

The sciatic nerve is more accurately five nerves that come together on the right and left sides of the lower spine. Technically, the fourth and fifth lumbar nerves and the first three nerves in the sacral spine come together and merge into the unified sciatic.

3. WITHOUT SCIATIC NERVES, YOUR LEGS WOULD BE WEAK NOODLES.

"The sciatic nerve gives feeling and strength to the muscles and skin of the calf and foot, supplies sensation from the joints, bones, and just about everything else below the knee," says Fishman.

4. THE SPINAL CORD'S CONNECTED TO THE THIGH BONE.

The nerve connects the spinal cord with the outside of the thigh, the hamstring muscles in the back of the thigh, and the muscles in your lower leg and feet. This is why sciatic nerve impingement often results in muscle weakness, numbness and/or tingling in the leg, ankle, foot, and toes.

5. INJURIES TO THE SCIATIC NERVE OFTEN AFFECT THE CONNECTION TO THE BRAIN RATHER THAN THE NERVE ITSELF.

After severe spinal cord injury, the nerve itself is often just fine, but the connection between it and the brain has been severed, Fishman says. Until now, there's been no way to fix such injuries, but "recent work with stem cells has begun to restore the connection in dogs and other animals."

6. BACK INJURIES ARE THE MOST COMMON CAUSE OF SCIATIC PAIN.

A variety of lower back problems can lead to pain that radiates along the sciatic nerve. Most commonly, sciatica pain is caused when a herniated disc at the L5 (lower lumbar back) irritates the S1 (sacrum) nerve root in the lower spine. The exiting nerve roots are highly sensitive, and the bits of the disc that herniate contain inflammatory proteins such as interleukin and tumor necrosis factor that can also aggravate the nerve.

7. SCIATIC PAIN CAN BE A MEDICAL EMERGENCY.

In a small number of people, a condition called cauda equina syndrome (so named because the nerve bundle at the base of the spinal cord resembles a horse's tail) can masquerade as sciatica—but it also usually causes weakness that extends to bowel or bladder incontinence and sometimes weakness or loss of sensation in the legs that gets progressively worse. In this case, immediate medical attention should be sought, and recovery may not be as quick as with common sciatica.

8. ANCIENT GREEKS AND ROMANS COULDN'T DISTINGUISH BETWEEN JOINT AND NERVE PAIN …

When the ancient Greek and Roman physicians were treating the pain we now commonly know as sciatica, they believed it stemmed from "diseases of the hip joint," according to a 2007 study in Spinal Cord. It wasn't until 1764, write the authors, "that leg pain of 'nervous' origin was distinguished from pain of 'arthritic' origin."

9. …AND HIPPOCRATES TREATED IT WITH THE BOILED MILK OF A FEMALE ASS.

Among the many treatments Hippocrates and his ilk came up with for this painful condition were: "Fumigations, fasting, and subsequently, laxatives, and ingestion of boiled milk of the female ass." In his Treatise of the Predictions, Hippocrates noted that elderly patients with "cramps and colds at the loin and the legs" would experience their pain for up to a year, whereas young people could be free of pain in about 40 days.

10. SCIATICA DERIVES ITS NAME FROM THE 15TH CENTURY.

The modern name for the disease, according to Fishman, comes from 15th-century Florence. "They called sciatica ischiatica, since they thought it came from tuberculosis that worked its way down to the ischial tuberosity (the sit-bones)," Fishman says. These medieval doctors had the cause wrong, but the name stuck.

11. SOMEWHERE BETWEEN 1900 AND 1925 PHYSICIANS CONNECTED HERNIATED DISCS TO SCIATIC PAIN.

Different researchers in different countries began to make sciatic breakthroughs when doing autopsies on corpses with fractured or herniated discs, where they noticed compression on the sciatic nerve.

12. WEIGHT HAS LITTLE INFLUENCE ON SCIATIC PAIN, BUT HEIGHT DOES.

A 1991 cross sectional study of 2946 women and 2727 men published in Spine found that neither gender nor body mass made any difference in the likelihood of developing sciatica. Body height did, however, in males between the ages of 50 and 64, with taller men being more likely to have the condition. Other studies have found a similar link [PDF]. Over 5'8"? Your risk is higher. 

13. SUFFERING FROM SCIATICA? YOU'RE NOT ALONE.

Sciatica has a surprisingly common negative impact on daily life. "Low back pain and sciatica are the second biggest reason for lost days of work—just behind the common cold," says Fishman. The condition is most commonly found in people over 50 and rarely seen in anyone under 20 years old—and then it most often has a genetic cause.

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