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By Adam Dachis

10 Stubborn Body Myths That Just Won't Die, Debunked by Science

Hair grows back thicker when you shave it! Reading in dim light turns you blind! Peeing on a jellyfish sting will soothe the pain! The way our bodies work is a bit of a mystery, and our desire to unlock its secrets has led to a vast amount of misinformation. Many of these false notions are more widely believed than the truth. We took our healthy skepticism and a bunch of research to find the truth behind some of the most common myths about our bodies. Here's what we learned.

Title image remixed from originals by Z-art (Shutterstock), Leremy (Shutterstock), and myVector (Shutterstock).

Note: Knowledge is power, so as we see it, misinformation makes us weak. Our myth-busting series aims to root out common myths so you can make better, more informed decisions.

Myth 1: Body Hair Grows Back Thicker When You Shave It

You might remember that episode of Seinfeld where Jerry decides to shave his chest despite warnings that it will grow back twice as thick. Although the myth proves to be true on television, it's very much false in the real world. If shaving caused hair to grow in much thicker, balding men would be shaving their heads for hair loss prevention. Children's health researcher Rachel C. Vreeman and assistant professor of pediatrics Aaron E. Carrol put this myth to rest:

Strong scientific evidence disproves these claims. As early as 1928, a clinical trial showed that shaving had no effect on hair growth. More recent studies confirm that shaving does not affect the thickness or rate of hair regrowth. In addition, shaving removes the dead portion of hair, not the living section lying below the skin's surface, so it is unlikely to affect the rate or type of growth. Shaved hair lacks the finer taper seen at the ends of unshaven hair, giving an impression of coarseness. Similarly, the new hair has not yet been lightened by the sun or other chemical exposures, resulting in an appearance that seems darker than existing hair.

Basically, shaved hair feels coarse and that leads you to believe it's thicker. In reality you're just fooling yourself and your hair remains the same.

Photo by Phil and Pam Gradwell.

Myth 2: Calories Counting Is All That Matters for Weight Management

We might like to believe that calories-in-equals-calories-out is a sufficient weight loss theory, but that means we have to accept our bodies are pretty simple. While consuming fewer calories can certainly have an impact, not all foods have the same impact once we stuff them down our throats. If you want to think about it in a very simple way, consider the difference between a candy bar and a cucumber. They taste different, they consist of different nutritional elements, and are not the same thing. It doesn't make sense that they'd be used by your body in the same way.

The problem with the idea of calories being the only necessary metric is that we think of a calorie as a physical thing. Calories are just a means of measuring heat, and they weren't initially a term used in reference to food. A calorie, according to Wikipedia, "approximates the energy needed to increase the temperature of 1 gram of water by 1 degree Celsius." Basically, calories are a measurement and not something your body uses for fuel. What your body does use is what it finds in the foods and liquids it digests. If you put crap in your body, you're not going to be better off just because of a low-calorie rating.

The way your body processes sugar is an excellent example of how different foods yield different results. While the idea that health can come from eating a magic number of calories each day, the reality is that foods and your body are more complex. Pay attention to the composition of the foods you eat and you'll wind up with much better results.

Photo by Victor Hertz.

Myth 3: You Need Eight Hours of Sleep Per Day

We're told we need to sleep eight hours each night, and while that's true for some it isn't true for all. The Hindustan Times points to a European study that showed people who possessed a gene known as ABCC9 could sleep for significantly fewer hours than the average person. Finding the same gene in fruit flies, the scientists found that by manipulating it they could also manipulate the amount of time the fruit flies spent in a restful state. When we asked you how much sleep you require, the results varied quite a bit. For some, eight hours was necessary. For others, it was too much. Your experiences match this study.

Additionally, Wired Magazine profiled a chemical called Orexin A that is believed to work as a sleep replacement. It's already present in humans in limited amounts, and when depleted causes us to feel tired. Since its discovery, Orexin A has been fashioned into a nasal spray (for testing purposes) to find out if it can be used as a treatment for narcolepsy. In a study at UCLA, a few scientists decided to make some tired monkeys snort the chemical:

The monkeys were deprived of sleep for 30 to 36 hours and then given either orexin A or a saline placebo before taking standard cognitive tests. The monkeys given orexin A in a nasal spray scored about the same as alert monkeys, while the saline-control group was severely impaired.

While information about Orexin A is still rather new, it points to the possibility that sleep may not be as relevant as we think it is. Either way, while eight hours of sleep isn't a bad recommendation it is definitely not a necessity for everyone.

Photo by Joi Ito.

Myth 4: Reading in Dim Light Ruins Your Eyes

Reading in dim light is supposed to be bad for you, which is somewhat evidenced by a surviving bedside lamp and book light industry. If not, you've certainly been told to turn on a light when reading in the near-dark. While reading without sufficient lighting can cause eye strain, according to children's health researcher Rachel C. Vreeman and assistant professor of pediatrics Aaron E. Carrol it won't cause any serious and permanent damage:

The majority consensus in ophthalmology, as outlined in a collection of educational material for patients, is that reading in dim light does not damage your eyes. Although it can cause eye strain with multiple temporary negative effects, it is unlikely to cause a permanent change on the function or structure of the eyes. Even in patients with Sjögren's syndrome (an autoimmune disease that features inflammation in certain glands of the body), decreased functional visual acuity associated with strained reading improves when they stop reading. One review article on myopia concludes that increased use of one's eyes, such as reading in dim light or holding books too close to the face, could result in impaired ocular growth and refractive error. The primary evidence cited was epidemiological evidence of the increased prevalence of myopia and the high incidence of myopia in people with more academic experience. The author notes that this hypothesis is just beginning to "gain scientific credence." In the past reading conditions involved even less light, relying on candles or lanterns, so increased rates of myopia over the past several centuries does not necessarily support that dim reading conditions are to blame. In contrast to that review, hundreds of online expert opinions conclude that reading in low light does not hurt your eyes.

For more information on the studies mentioned above, read this.

Photo by Giles Cook.

Myth 5: Urinating on a Jellyfish Sting will Sooth the Pain

The popular TV show Friends once had an episode where Monica was stung by a jellyfish and Joey remembered that urinating on the sting would soothe the pain. This was a situation for comedy—as the show was a sitcom, after all—but it still helped to propagate the myth that peeing on your friends is a good idea during the right situation. It's not. Mark Leyner and Dr. Billy Goldberg, authors of Why Do Men Have Nipples?, explain:

The following guideline can be applied to most jellyﬁsh stings: The patient should remove any visible tentacles, using gloves if possible. The area of the sting should be rinsed with household vinegar. The acetic acid of the vinegar can block discharge of the remaining nematocysts (stinging cells) on the skin and should be applied liberally. If vinegar is not available, salt water can be used to wash off the nematocysts. In laboratory tests, urine, ammonia, and alcohol can cause active stinging cells to ﬁre, which means applying them has the potential to make a minor sting worse, so urinating on a jellyﬁsh sting is both gross and painful.

So if you're going to pee on anyone, make sure it's for your mutual enjoyment. Jellyfish are not a good excuse.

Photo by Sam Howzit.

Myth 6: Your Slow Metabolism Makes You Fat

When you have a fast metabolism, your body is burning more calories. That means that fit and healthy people have faster metabolisms, right? Not necessarily. ABC News interviewed Dr. Jim Levine, an obesity researcher at the Mayo Clinic, who studied the human metabolism in both thin and heavy people. What he found was the opposite of the myth we believe. Referring to lean patient Kathy Strickland and heavier patient Dawn Campion, he said:

Dawn's numbers are actually higher because we find continuously is that people with weight problems who have obesity have a higher basal metabolism compared to people who are lean. Your basal metabolism is the calories you burn to keep your body going, so if your body is bigger of course your basal metabolism is greater. If your body is smaller your basal metabolism is less.

Dr. Levin inferred that the weight problems in his patients was due less to the speed of their metabolism and more due to their sedentary lifestyles. That is, of course, only one part of the equation. Gaining unwanted weight can stem from an unhealthy diet, lack of exercise, and a number of other problems as well. It's a complicated problem, and your metabolism isn't necessarily to blame.

Photo by Tony Alter.

Myth 7: You'll Catch a Cold from Cold (and Wet) Weather Conditions

Did your mother ever tell you to put on a jacket or you'll catch a cold? Did you ever feel like you were coming down with something nasty after taking a dip in cold water only to be exposed to freezing air? While your comfort levels may have been reduced, you can't actually catch a cold from feeling cold. It's a virus—rhinovirus, to be exact—and you need to catch it through transmission. Mark Leyner and Dr. Billy Goldberg, authors of the book Why Do Men Have Nipples?, explain:

Cold or wet weather does not cause a cold, but nobody seems to want to accept this. The is common cold is caused by a virus. These viruses are everywhere and it is difficult to avoid them. When you are exposed to someone who has a cold, you are more likely to get ill yourself, so be careful about close contact and definitely wash your hands. Not getting enough sleep or eating poorly can also reduce your resistance to infection. Remember that antibiotics won't fight your everyday cold. Antibiotics work only against bacteria. To take care of a cold, rest, eat well, and a little chicken soup couldn't hurt.

But if that's true, why do people contract a cold more often in the Winter? Doctors don't have a certain answer, but according to the New York Times there are a few working theories. Because colds are spread by transferring the virus from one person to another, you need to be in contact with other people. People spend more time indoors during the Winter, and so you often find yourselves 1) around them, and 2) in an enclosed space. If one person gets sick in a household, office, or wherever, there's a good chance that virus will spread. As you should any time of year, keep your distance from the contagious.

Photo by Faith Goble.

Myth 8: More Heat Escapes Through Your Head

Heat rises, and your head is generally warm, so it would stand to reason that walking around outside with your head uncovered isn't the best plan if you want to stay nice and toasty. While that idea seems to make sense, you're not going to lose more heat through your head than you will from pretty much any other part of your body. According to Children's health researcher Rachel C. Vreeman and assistant professor of pediatrics Aaron E. Carrol, wearing a hat will just keep your head warmer:

This myth probably originated with an old military study in which scientists put subjects in arctic survival suits (but no hats) and measured their heat loss in extremely cold temperatures. Because it was the only part of the subjects' bodies that was exposed to the cold, they lost the most heat through their heads. Experts say, however, that had this experiment been performed with subjects wearing only swimsuits, they would not have lost more than 10% of their body heat through their heads. A more recent study confirms that there is nothing special about the head and heat loss. Any uncovered part of the body loses heat and will reduce the core body temperature proportionally. So, if it is cold outside, you should protect your body. But whether you want to keep your head covered or not is up to you.

For more information on the studies mentioned, read this.

Photo by Jenny Downing.

Myth 9: High Cholesterol Causes Heart Disease

Until writing this article, I believed high cholesterol was the primary contributing factor towards heart disease. It's been a myth I've been told my entire life because I'm prone to cholesterol problems and have watched my levels very carefully since I was a child. According to Dr. Malcolm Kendrick, and many others, the data doesn't consistently link high cholesterol with heart problems. It seems the real culprit is more commonly high blood pressure, and cholesterol problems may have found themselves grouped in because the two issues often appeared together. This doesn't mean you want higher levels of cholesterol (with the exception of your HDLs), but that if you're worrying about a heart attack it's not the first sign of trouble.

Photo by Healthy Living.

Myth 10: It's Dangerous to Wake a Sleepwalker

It's actually dangerous to not wake a sleepwalker, but many have believed this myth for ages because, perhaps, a few of them have gotten smacked when they woke up their startled somnambulatory friends. Sleepwalkers are certainly prone to feeling that surprise when they don't wake up in their beds but, rather, at the outer limits of their camping grounds. (Oh wait, that was me when I was 10.) Because this is so disorienting, many woken sleepwalkers won't know who you are and become frightened. That said, letting them just walk wherever they want is far less safe than a little fear. The New York Times interviewed Dr. Ana C. Krieger, director of the Sleep Disorders Center at New York University, who suggested that the best thing to do is guide a sleepwalker back to bed. Wake them if you have to, but better to just help them get to where they should be in the first place.

Photo by Peter Hess.