Seven-Year Gut Gum and Other Tales We're Debunking Right Now

You caught a cold because you went outside with wet hair. Grandpa got arthritis from cracking his knuckles too much. George Jr. has a pimple because he ate chocolate.

We all love medical myths. They provide explanations to the puzzling world of health and human biology. But medical myths are either unproved or simply untrue. Real medicine is based on evidence from scientific study. Myths can’t be proven, which can lead us to do things that are dangerous or sometimes simply silly. (Are you still feeding that cold and starving that fever?)

It’s time for some schooling. Here are a few medical myths we’re debunking:

When you’re pregnant you’re eating for two – Doctors actually recommend increasing your amount of certain nutrients, but not adding too many extra calories. In fact, pregnancy requires only an extra 300 calories a day, which is the equivalent of a slice of whole grain bread and a tablespoon of peanut butter. Bummer.

Sugar makes kids hyperactive – Sugar can give a short-term energy boost, but that’s not hyperactivity. Most likely, children become over-excited when given sugar because it’s during a party when the rules of conduct bend a bit. That’s not to say that parents shouldn’t limit high calorie, sugary foods –just don’t think it’s going to make Lil’ Sophia any less unruly.

You’ll get the flu from the flu vaccine - The Centers for Disease Control and Prevention (CDC) recommends that everyone 6 months of age or older be vaccinated annually against influenza. If you get the flu after having a flu shot, it’s probably because the vaccine didn’t have time to give you immunity. Consider this: Maybe you ran to get your flu shot because everyone in your office was sneezing on you.

Chewing gum stays in your stomach for seven years – No, you haven’t been stockpiling Trident in your gut all that time. The truth is, we eat many things that are indigestible. But your digestive system is very efficient and anything that it doesn’t absorb gets passed along.

If you shave it, the hair will grow back coarser and darker – This has been a debate going on for almost 100 years. In fact, a clinical trial way back in 1928 compared hair growth on shaved vs. unshaved hair patches and saw no difference. Why does it seem the hair is darker? It could be the new hair hasn’t been exposed to as much sunlight and shaved hair does initially seem blunter. Or it could be you’re buying into a powerful myth.

Eat something spicy, get an ulcer – Are you regretting that double bean burrito with extra hot sauce? There’s a lot to regret in that meal, but one thing is it didn’t give you an ulcer. Ulcers are sores in the lining of the esophagus, stomach and upper intestine usually caused by the bacterium Helicobacter pylori, not the Kolhapuri chicken you had at the Indian restaurant.

Tight bras cause cancer – No need to toss those uncomfortable underwire bras (unless you want to!) because scientific evidence does not support a link between wearing an underwire bra –or any type of bra –and breast cancer risk. This myth started after a 1991 study showed women who did not wear bras had a lower risk of cancer. However, the women who didn’t wear bras were more likely slenderer, which the authors stated could account for their decreased risk of cancer, but admitted that body type wasn’t a factor in the study.

Cracking your knuckles causes arthritis – It’s a chicken-and-egg game here. Knuckle crackers are more likely to have arthritis in the first place. But that’s not a “pass” on purposely cracking your knuckles in public. It won’t endear you to those around you.

You lose most of your body heat through your head – Despite the fact that you went through your childhood wearing unfashionable pom-pom winter hats, your head is just another body part. It doesn’t lose heat any faster than anything else that’s uncovered. We’re genuinely sorry about all that “hat hair” you endured.

Chocolate and fried foods cause acne – Here’s a myth that started with baby boomers who had more access to fast foods and candy than their parents. But those foods didn’t cause all their teen-age woes. Pimples are formed when pores are blocked by dead skin and too much sebum, which is probably over-produced by teen hormones.

Now that you have the facts, class is dismissed. But be careful when walking home. You know what they say about stepping on cracks in the sidewalk.

Is there anything we left off the list? Tell us your favorite fun medical myth in the comments below.

This information is not intended as a substitute for professional medical care. Always follow your health care professional's instructions.