Hit or myth: The truth behind Mom’s medical advice

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FARGO - We heard these bits of information so often that we’re now repeating them to our kids.

“Turn on the light. You’ll ruin your eyes,” Dad said. “No swimming after lunch or you’ll get a cramp,” Mom said. “Don’t cross your eyes or they’ll grow that way,” Grandma said.

But is there any truth in these medical mom-isms? Which are rooted in truth, and which are simply folklore?

To set the record straight, we talked to four medical experts: Vonda Eidenschink, certified physician’s assistant at MeritCare; Rebecca Joyce, nurse practitioner at MeritCare; Lori Schmidt, nurse practitioner at Hendrix Health Center, Minnesota State University Moorhead; and Dr. Margaret Lewin, medical director for Cinergy Health.

Here’s what we found:

Reading in dim light ruins your eyesight.

Moms have preached this for generations, but there’s no scientific evidence to support it.

Reading in low light can cause temporary eye strain, which goes away once you return to bright light.

Still, the practice of reading in poor light has been blamed for increasing rates of myopia, even though, as medical experts told Newsweek magazine in 2007, we are living in the best-lit conditions the world has ever seen.

Coffee will sober you up.

Java will stimulate you and make you feel more alert, but it will not hasten elimination of alcohol from the blood stream, Lewin says.

The only solution: Giving your liver time to metabolize the alcohol. On average, it takes your body about an hour to process one alcoholic drink, although that’s affected by factors such as gender, body weight, food most recently consumed and individual liver function.

A nip of “the hair of the dog that bit you” will ease a hangover.

False, Joyce and Eidenschink say. The only way to avoid a hangover is to drink in moderation or not at all.

Cold, wet weather will make you sick, as will going to bed at night with a wet head.

There’s no direct correlation, Schmidt says. Colds are caused by a viral infection, specifically a rhinovirus, which is transmitted by direct contact or via particles in the air, the health experts say.

It’s more likely that cold weather became blamed for sickness because we are forced to stay inside more during winter, which makes it easier to breathe in each other’s cold-causing pathogens.

Gum and fingernails will stay in your stomach (or be stored in your appendix) for seven years.

Most gums today are made using synthetic polymers, which are mostly indigestible, MeritCare experts say. Even so, the plastic part of the gum will still flow through the intestinal tract and be excreted in a few days.

Fingernails are made of keratin, a protein that’s not easily digested, Eidenschink and Joyce say. Like gum, they will pass through the GI tract in several days and be excreted.

There are very rare cases reported in medical literature in which children swallow so much gum they form a bezoar – a hard, indigestible mass of material – in the esophagus and intestinal tract, causing obstruction, Lewin says.

The flu shot can give you the flu.

The flu shot is made from a killed virus, so it cannot make you sick. Likewise, the intranasal spray is attenuated (meaning “weakened”) so it shouldn’t cause flu either, Schmidt says.

This common misconception probably stems from the body’s “exuberant immune response” to the shot or spray, which can cause achiness and low-grade fever in some people for a day or so, Lewin says.

Cracking your knuckles causes arthritis.

There’s no evidence that cracking knuckles will cause damage such as arthritis to the joints, the MeritCare health providers said.

However, knuckle-cracking is associated with injury of the ligaments surrounding the joint or dislocation of the tendons. These injuries improve with conservative treatment.

Anywhere from 40 to 90 percent of body heat escapes through your head.

Not true, Lewin says. The amount of heat loss is determined by the surface area to the cold. The head myth is based on a U.S. Armed Services experiment in the ’70s in which soldiers were exposed to extreme cold, properly bundled up except for their heads.

Since their heads were the only body parts exposed, they registered as the only part through which body heat escaped. If they’d left only their legs exposed, they’d have exposed more surface area and lost even more heat.

Eating carrots will improve your night vision.

It’s true that carrots contain vitamin A and that a vitamin-A deficiency may lead to poor vision, but consuming an excess of the vitamin will not give you Superman-caliber sight, optometrist Harvey Moscot said in an online article on common eye myths.

However, certain foods will improve overall eye health. Egg yolks and dark green vegetables, such as spinach and broccoli, contain lutein, which can protect against macular degeneration.

It’s dangerous to swim a half-hour after eating.

Yes, the digestive process diverts some circulation from the muscles, so there may be some cramping or discomfort, but there’s never been a documented case of drowning caused by swimming immediately after eating, Lewin says.

Neither the American Red Cross nor the American Academy of Pediatrics makes any recommendations for the amount of time to wait after meals.

You should drink at least eight glasses of water a day.

This myth may have originated from a 1945 article from the National Research Council that claims a “suitable allowance” of water for adults is 2.5 liters a day, according to Newsweek magazine. (The article also notes that much of that water is already found in the foods we eat.)

We also get enough fluids from our daily intake of juice, milk and even some caffeinated drinks. In fact, you can get a condition called “water intoxication” from drinking too much water.

Don’t cross your eyes or they’ll stay that way.

This belief is based more on a fear that kids will never stop teasing each other than it is on any facts. “Muscles cause eye movements and – like any other muscle – don’t suddenly give up function by being activated in any direction,” Lewin says.

Someone with a concussion should be kept awake for at least 24 hours.

No, although it’s a good idea to monitor the person closely for 24 hours and wake him up every few hours with questions like, “Do you know where you are now?” or “Do you know what month it is?”

If the injury actually caused the person to lose consciousness or lose recall of the incident, they need to see a physician, Schmidt says.

Other signs of concern include irritability, memory loss, speech or vision changes, vomiting, headache, dizziness, deep sleep, difficulty being awakened, extreme sleepiness or seizure. All these signs can indicate swelling of the brain, Schmidt says.

Coffee will stunt your growth.

False, Eidenschink and Joyce say. The thinking used to be that caffeine would reduce bone density, thus curbing growth. But studies show there is no difference in the bone density of heavy caffeine drinkers and those who consume barely any caffeine at all.

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