12 Health Mysteries Explained
What Is Brain Freeze?
It’s a pain in your head that occurs when the nerves on the roof of your mouth are hyperstimulated by cold foods, like ice cream and frozen drinks. The nerves are in your mouth, but the nerve center is in your brain, “so that’s where you feel the pain,” says Seymour Diamond, M.D., a headache specialist in Chicago and the executive chairperson of the National Headache Foundation. “This is known as referred pain.” Why do humans experience pain in one place when the stimulus is elsewhere? No one knows for sure. “We do know that migraine sufferers are more prone to ice cream headaches,” Diamond says. “We also know that eating slowly and sipping slowly seem to reduce the effects of the cold. Once the headache sets in, the fastest way to make it go away is to drink something lukewarm.”
Why Do You Have Earwax?
To keep foreign matter from invading ear canals. Earwax, or cerumen, is produced by glands in the outer ear to protect the inner ear from infection. The sticky substance prevents dust, dirt, and bugs from getting in. “Just leave it alone,” says Andrew Cheng, M.D., an ear, nose, and throat specialist at the Manhattan Eye, Ear and Throat Hospital. Ears are self-cleaning: The wax slowly moves up and out of the ears on its own, dries up, and flakes off or washes away when you shampoo your hair. If you’re a Q-tip addict, clean just the outside of your ears. “Ear canals are like dead-end streets,” Cheng says. “Q-tips just push wax further in.” You could also accidentally scratch your ear canal or even puncture the eardrum.
Why Do You Get Goose Bumps?
Because you’re cold or frightened. When you feel chilled, the muscles around your hair follicles contract, causing the hairs to stand up to create a layer of insulation, explains Richard Potts, Ph.D., an anthropologist and the director of the Human Origins Program at the Smithsonian Institution’s National Museum of Natural History, in Washington, D.C. All mammals share this hair-raising trait. But "humans don’t have enough body hair for the response to make a difference; it’s a vestigial reflex left over from when we had furry coats,"Potts says. The goose bumps people get when they’re scared may be another vestigial reflex. Potts and others theorize that aeons ago, when the plentiful hair on our ancestors’ bodies stood on end, they appeared more menacing, and, he says, “predators would move on to look for less imposing prey.”
Are Carrots Really Good For the Eyes?
"Yes, they are, along with all other foods rich in vitamin A," says Michael F. Marmor, a professor of ophthalmology at the Stanford University School of Medicine. The body uses vitamin A to support nerve cells in the retinas that help maintain normal vision. People who are deficient in A are susceptible to a host of vision problems, such as night blindness. Many red, yellow, orange, and leafy green vegetables―including sweet potatoes, kale, mangoes, and papayas―contain vitamin A, as do eggs and liver.
Why Do Lips Thin as You Age?
The older you get, the less collagen you produce. And collagen, a protein that supports the body’s soft tissue, is what gives lips their pleasing plumpness, says D’Anne Kleinsmith, M.D., a dermatologist in Bloomfield Hills, Michigan. The sun’s ultraviolet rays can also cause collagen to break down and lips to thin. “One way to help preserve the fullness of your lips,” Kleinsmith says, “is to protect them from the sun by wearing a lipstick or lip balm with sunscreen.”
Why Do Teens Sleep Late?
They’re not lazy; they can’t help it. During childhood, melatonin, the hormone that regulates the wake-sleep cycle, is secreted by the pineal gland early in the evening. When puberty hits, from around ages 10 to 14, melatonin is released later, around 9 p.m. or 10 p.m. “This shift often makes many teenagers incapable of falling asleep before 11 at night,” says teen sleep expert Mary A. Carskadon, Ph.D., a professor at Brown Medical School and the director of the Bradley Hospital Sleep and Chronobiology Research Laboratory, in Providence. “Since teens still need about nine or more hours of sleep, they try to make up for the time they’ve lost at night by sleeping in.”
What Causes Hiccups?
Excessive eating, alcohol, excitement, or stress can overstimulate the phrenic nerves, which control the diaphragm. The diaphragm then contracts involuntarily. At the same time, the glottis, the part of the larynx where the vocal cords are located, closes up, says Patricia Raymond, M.D., a gastroenterologist in Chesapeake, Virginia. The result is the spasms and the odd hic sound that repeat every few seconds. A typical case of the hiccups lasts only a few minutes, but some can last much longer. While there’s no proven cure, Raymond suggests trying an action that resets the phrenic nerves (akin to rebooting your computer when it’s frozen), such as holding your breath or breathing into a paper bag.
Why Do So Many Women Have Cold Hands and Feet?
Blame it on circulation. “The nerves that control blood flow to the hands and feet are more sensitive in women than in men,” says Mark Eskandari, M.D., a vascular surgeon at Northwestern Memorial Hospital, in Chicago. “So when the temperature drops, their vessels constrict more, warming blood flow slows, and their extremities feel cold.” Women also have lower blood pressure than men. “When they’re cold or stressed and their blood pressure drops, blood is redirected to the heart and away from the hands and feet,” he says. "Some experts believe that women tend to hold heat in the core, where the heart and uterus are, so they can protect developing fetuses," notes James Applegate, a family doctor in Grand Rapids, Michigan. But this is just a theory.
Why Do Joints Crack?
When you stretch a joint by, say, pressing down on your knuckles or twisting your spine, you cause small air bubbles that form between the sacs in the joints to pop. These sacs, called bursas, help cushion the spaces between the bones and keep them lubricated. As creepy as the sound can be, cracking is usually harmless and has no effect on the bursas. “Despite what your mom may have told you, cracking your knuckles or ankles or knees or any other joint doesn’t cause arthritis,” Applegate says. But it doesn’t do your joints any good, either. “Any feel-good benefit people claim from joint cracking,” he says, “is psychological.”
Why Do Some People Have Whiter Teeth Than Others?
Just like the color of your eyes and hair, the natural tint of your teeth is hereditary. “Some people have very white enamel―the thin coating on the surface of teeth―while other people’s enamel has a more yellow hue,” says Richard Price, a dentist in Newton, Massachusetts, and a spokesperson for the American Dental Association. Environmental factors play a role, too. “Teeth are kind of like the rings on a tree,” Price says. “They tell a lot about a person’s health and history.” Taking the antibiotics tetracycline or amoxicillin as a child can affect the calcification process, causing discoloration. Certain foods can also darken teeth. “If a substance will stain a carpet,” Price says, “it will stain your teeth.” Coffee, tea, cola, and red wine are common culprits. Frequent cleanings can help, but severe food stains may require a whitening product or procedure.
Why Do People Get Sick More Often in the Winter?
“Lots of hypotheses, not one perfect answer,” says William Schaffner, M.D., chairman of the department of preventive medicine at the Vanderbilt University School of Medicine, in Nashville. A leading theory is that confinement breeds infection. “In winter,” Schaffner says, “we spend more time indoors, in rooms that may not get a lot of circulation, giving us more opportunities to be exposed to respiratory viruses.” The winter air, inside and outside, also tends to be less humid, drying nasal passages and making them more vulnerable to viral invasion. Still, Schaffner adds, the cold environment itself has not been proven to make people get sick in the winter.
Why Is Yawning Contagious?
No one knows for sure, but a study published in a recent issue of the journal Cognitive Brain Research theorizes that yawning in response to someone else’s yawn may be an empathetic response, similar to laughter. “A yawn can be triggered not only by seeing a person yawn but also by hearing, reading about, or even just thinking about yawns,” says Steven Platek, Ph.D., a professor of psychology at Drexel University, in Philadelphia, who directed the research. Platek and his colleagues believe that contagious yawning may be a primitive way of modeling our feelings after other people’s.