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In the great tradition of debunking stuff, here are 10 more myths involving the human body that, while refuted by science, persist in popular culture.

I will provide a short summary of each of the 10 myths below. For more information, read the original article here.

Correcting 10 Myths about Your Body

Body Hair Does Not Grow Back Thicker When You Shave It

Since 1928 and studies from then on, clinical trials show no evidence that shaving increases thickness or rate of hair growth. Because shaving removes the dead portion of the hair and not the live portion, it is implausible that growth would be affected. Hair that comes out of the follicle appears to be more coarse because it lacks the tapered ends of unshaven hair, and because it has not been lightened by the sun when it begins to grow back it looks darker. Both of these factors contribute to belief in the myth.

Think of it this way: if shaving did increase hair growth and thickness, every bald man who took the time to shave everyday would soon have a thick head of hair. Do we ever see this? [No]

More posts about hair: Hair and fur are the same thing

Calories Counting Is Not All That Matters for Weight Management and Health

Although reducing your caloric intake will reduce your weight, all foods that have equal calories are not the same. For example, you would not become a healthy person from simply restricting calories and living on lard (pure animal fat). Because a calorie is a measurement of energy and not a specific food component like protein or carbohydrates, simply counting calories is a huge oversimplification of healthy eating.

Your current weight, the weight you want to lose, the nutritional balance of your diet, the calories you burn and muscles you build through exercise, and the amount of time you’re sedentary each day are all elements that play into your health and potential for fat loss.

You Do Not Really Need Eight Hours of Sleep Per Day

Sleep is a highly variable thing that differs for different people. Some studies have shown that different genetic factors may play a role in how much sleep a person really “needs.”

The remedy is similar to that of the myth that you have to drink eight glasses of water per day: if you are tired, sleep for as long as you feel the need to. Your body is a remarkably good self-regulating machine. Tired? Take a nap. Wide awake after five hours of sleep? Get some work done.

Reading in Dim Light Does Not Ruin Your Eyes

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.

Reading in low light may cause eye strain, but no permanent damage.

Related posts: Sitting too close to the TV won’t hurt your eyes

Urinating on a Jellyfish Sting will Not Soothe the Pain

In laboratory tests, urine and its constituents cause the cells from the jelly to fire more. When urinating on a friend who has been stung, you are both gross and doing more harm than good.

Full post on this myth to come in a few days.

Your Slow Metabolism Does Not Make You Fat

Dr. Jim Levine, an obesity researcher at the Mayo Clinic, has 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.

Your weight is a complex equation and obesity can result from lack of exercise, sedentary lifestyle, and an unhealthy diet. Your metabolism is not necessarily to blame. Again, trying to oversimplify the body’s processes regularly results in misconceptions.

You Will Not Catch a Cold from Cold (and Wet) Weather Conditions

Bottom line: the common cold is caused by a virus (over 200 different viruses, in fact) and has nothing to do with the temperature outside.

Why do people seem to get more colds in winter? Some possible explanations: when it’s cold outside people spend more time indoors around other people, making the spread of viruses that much easier or it is a product of the confirmation bias, where we remember all the times that we got cold in winter and forget all the times when we do not (supporting the belief).

More Heat Does Not Escape Through Your Head

You don’t lose more heat through your head than you would through other parts of your body that are uncovered in cold weather. If certain variations of the myth were true and we lost 40% of our heat through our head, whenever we went outside without a hat on it would feel like we went outside without pants, socks, and shoes.

Related post: How much heat do you lose through your head?

You Cannot Cure a Snake Bite by Sucking Out the Poison

I don’t know where you heard this one but do not do it! Especially if the bite is recent, sucking on the wound can transfer venom from the wound directly into your body, creating a situation where the person who was supposed to help collapses.

If you want to help, wash the wound, immobilize the bitten area (or apply a tourniquet to slow blood flow from the bitten area) and keep it below the level of the heart (if possible, to make gravity fight against the flow of veonmized blood), and seek medical help.

It’s Not Dangerous to Wake a Sleepwalker

A person who is woken up from an episode of sleep walking or somnambulism will probably feel disoriented and frightened but it will certainly not kill them (and they will not go into a sleep-rage and kill you).

In fact, it is more dangerous not to wake a sleepwalker. Many injuries result from sleepwalkers losing their balance, tripping, walking into objects, or acting out their dreams (jumping out a window, trying to drive, etc.). The best idea would be to gently guide a sleepwalker back to their bed and to wake them up if necessary. It won’t hurt them and you can keep them from hurting themselves.

[Via Lifehacker, Skepchick]