8 Old Wives' Tales and the Science Behind Them

 by Vivian Manning-Schaffel

Did your mom ever warn you against venturing outside into the cold with wet hair? Or has your grandma scolded you for jumping into a swimming pool less than 30 minutes after eating? When it comes to health, old wives tales abound. But are there kernels of truth to be found in them?


Did your mom ever warn you against venturing outside into the cold with wet hair? Or has your grandma scolded you for jumping into a swimming pool less than 30 minutes after eating? When it comes to health, old wives' tales abound. But are there kernels of truth to be found in them? And where do these seemingly far-fetched tales come from? Here are eight common health-related old wives' tales you might have heard growing up (or even into your adulthood) and the science behind them.

1. “Don’t Crack Your Knuckles -- You’ll Get Arthritis.”

Knuckle-cracking is a nervous habit we could probably all do without. Caused by the collapse of gas bubbles in the fluid that cushions our joints, it's highly addictive. According to 2011 study published in the Journal of the American Board of Family Medicine, between 25 and 54 percent of people have done it at one time or another. The good news: It won't cause arthritis. Several studies report no link between arthritis and knuckle-cracking, including one testimony from a Nobel Prize-winning doctor who cracked the knuckles twice daily every day on one hand for 50 years to disprove his own mother. After 50 years, he reported no difference in his hands. However, cracking knuckles has been found to cause a few other problems, like swelling, weakened grip, the dislocation of tendons and ligament damage around the joint. So even if it doesn't cause arthritis, it might be a good idea to give your knuckles a break.

Related: 9 Moves You Can Do Every Day for Better Joint Mobility

2. “You Should Stay Out of the Pool for at Least 30 Minutes After Eating.”

There are few things more excruciating to a kid than snacking by a pool and then having to wait half an hour to jump back in. Yet moms everywhere made the wait a requirement. Turns out, there's some truth to this old wives' tale, but it's not exclusive to swimming and depends on how much you've eaten. Any form of strenuous exercise shortly after eating a big meal can cause a "stitch," or a cramp in your stomach shortly thereafter. "Exercising shortly after a big meal isn't ideal because blood is drawn to your gut for digestion, which takes away from the working muscles," says Darren Morton, senior lecturer at Avondale College of Higher Education in Australia and the world's foremost researcher on "the stitch." "The body is cleverly designed to help us remember this by giving a feeling of discomfort or pain when we eat too much and then attempt to perform exercise. In short, it is probably safe enough to go swimming after a meal, but it probably won't be that enjoyable."

Related: Bulletproof's Dave Asprey on How to Biohack Your Best Self

3. “Feed a Cold, Starve a Fever.”

Generally, neither colds (nor fevers) tend to promote hunger by nature -- either you're too congested to taste anything or too lethargic to care much about food. A recent article in Scientific American claims the old "feed a cold, starve a fever" adage dates all the way back to the late 1500s, when a dictionary entry by John Withals claimed fasting was a "great remedy" for fever, because food was thought to generate heat in the body. Loosely corroborating this theory, one study, dating back to 1997, claims food restriction is one way organisms fight pathogenic invasion (aka germs). Another 2002 study from Holland actually supports the adage, having found that eating helps combat the kind of virus cells consistent with colds, while not eating helps your body to fend off bacteria and fever. Unless it's the flu. Then you should eat. Basically, you should do what you feel up to doing, including eating, but the most crucial part to kicking a cold or fever is constant rehydration to drain mucus and replenish fluids.

Related: 12 Not-So-Common Tips to Fend Off Cold and Flu

4. “Coffee Will Stunt Your Growth.”

File this old wives' tale under total malarkey. There doesn't seem to be a single study to prove there's even a kernel of truth in this old wives' tale -- with respect to children, anyhow. However, the USDA discourages serious caffeine consumption for children for other reasons. But coffee can provide many positive benefits for grown folks when consumed in moderation, such as protecting against Type 2 diabetes, easing Parkinson's disease symptoms and promoting heart health. So unless you've been medically advised otherwise, go ahead and pour yourself a cup.

Related: Coffee and 17 Other Foods With a "Bad" Rap That Are Actually Good for You

5. “Put on a Jacket or You’ll Catch Your Death.”

This old wives' tale is particularly popular and persistent -- possibly because it was recently established there may be some truth to it. In 2014, Yale researchers published a study in the Proceedings of the National Academy of Sciences of the United States of America revealing how rhinovirus, otherwise known as the common cold, grows more effectively at cooler temperatures in the nasal cavity than at warmer lung temperatures by diminishing antiviral immune response. By examining the immune response of mice incubated at 37 degrees Celsius versus 33 degrees Celsius when exposed to rhinovirus, researchers determined the immune response was, indeed, impaired in the mice in the lower temperature. So as temperatures drop, it might be worth your while to bundle up. However, it's not true that failing to put on a jacket will automatically result in you catching a cold. But if it makes mom feel better, isn't it worth it?

Related: 7 Surprising Foods to Combat Winter Colds

6. “The Flu Shot Gives You the Flu.”

A longstanding myth that makes the rounds each and every year, the idea that the flu shot gives you the flu is just that -- a myth. Medical experts almost unanimously endorse the flu shot, claiming it's the best line of defense against the potentially dangerous virus. Although the flu vaccine can have adverse side effects that mimic flu symptoms (like low-grade fever, headache and a sore throat) the Centers for Disease Control and Prevention says flu shots made with the flu viruses aren't infectious because the virus is inactivated or the vaccine is made with no virus at all (which is the case for recombinant influenza vaccine). It takes about two weeks from exposure to come down with symptoms, so the earlier in the season you get your flu shot, the better armed you'll be against the virus.

Related: How Vaccines Have Become Victims of Their Own Success

7. “Chicken Soup Will Cure Your Cold.”

Chicken soup has historically been a sick-day fave -- it was even endorsed by Maimonides, a medieval Sephardic Jewish philosopher and astronomer, as a cold remedy as far back as the 13th century. In this century, scientists have learned it's for good reason. It turns out chicken soup might really contain healing properties, though they're not sure which ingredient is specifically responsible for this effect. During a 2000 study published in CHEST (the journal of the American College of Chest Physicians), scientists learned the combination of ingredients in chicken soup (the one in the study contained chicken, onions, sweet potatoes, parsnips, turnips, carrots, celery, parsley, salt and pepper) have a mild anti-inflammatory effect on the body that reduces swelling in the upper respiratory system. Another 2012 study from the American Journal of Therapeutics tried to pinpoint the ingredient responsible by linking the compound carnosine, which is found in chicken, and a decreased inflammatory response associated with viral infections. But other studies have suggested it might be the garlic, onion or ginger that's responsible. And there's certainly something to be said for the steam helping to clear out your nasal passages. So next time you're under the weather, tell mom to keep the chicken soup coming.

Related: 8 Foods That Boost Your Immune System

8. “Eat Fish -- It’s Brain Food.”

In 2014, a group of scientists from UCLA published a study in the American Journal of Preventative Medicine, proving a weekly portion of baked or broiled fish was "positively associated" with grey matter in sections of the brain having to do with cognition and memory in the elderly -- even without factoring in the already established brain enhancement contributed by omega-3 fatty acids found in fish. In an interview in The Atlantic, lead scientist Cyrus Raji, M.D., said eating fish (doesn't matter what kind) even once weekly can make your hippocampus (the part of the brain responsible for memory and learning) larger by as much as 14 percent, an amazing finding, considering the population of those suffering from dementia is expected to double every 20 years -- numbers that make the fish entree on any menu that much more appealing.

Related: 13 Types of Fish to AVOID

What Do YOU Think?

Have you ever heard any odd health-related old wives' tales you'd like debunked? What are they, and where did you first hear them? Have you ever heard any of these on the list? Did you realize where they'd come from or the science behind them? Leave your thoughts, questions and suggestions in the comments section below!

Related: The Truth Behind 20 Diet and Exercise Myths


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