Here’s another installment on this series, which are among the popular posts in this blog.

1. Eat carrots, for it will improve your eyesight.

I am sure many of you have heard this from your parents and your grandparents. They even said that it is especially true for improving night vision. Or maybe you’re advising your kids this too, telling them this will prevent them from needing eyeglasses. The scientific proof? Have you ever seen a rabbit wearing glasses?

Although this sounds like just another way for parents to get their children to eat vegetables, there’s actually some truth to this advice. Whether or not eating carrots will stop the need for ever wearing glasses is not accurate though.

Carrots contain a massive amount of beta-carotene, a precursor of vitamin A. Sweet potatoes, squash, and green leafy vegetables are also good sources of beta-carotene. Vitamin A is needed to form the protein rhodopsin, a light-sensitive pigment found in the retina of our eyes.

Vitamin A is not only key for good vision, it is also essential in healthy immune system and cell growth. Though poor nutrition may be one cause, there are many other reasons that can results to eyesight impairment that may need correctional glasses.

The tale for eating carrots was propagated during World War II,  when the British claims that their pilot’s success in gunning down German aircrafts even at night is due to their carrot-enrich night vision, and thus encourage civilians to eat locally grown vegetables. They made up this propaganda to cover-up their recently adopted radar technology, and kept this invention a secret.

2. Wound from a rusty nail will cause tetanus.

Folks say that stepping on a rusty nail or any rusty object, can cause rust to enter the body, and lead to tetanus. This could include eating food cooked in a pot that has some rust on it. These are half-truths. Though I would not recommend using rusty pots nor stepping on rusty nails.

I remember our old car in the Philippines with some rust on it, that some friends jokingly told me that they might get tetanus from scraping into our car.

Tetanus is an infection cause by the bacteria Clostridium tetani. These bacteria or its spores are usually found in the soil or dirt. This bacteria can enter the body through breaks in the skin like cuts or puncture wounds, but it’s not the rust itself is the problem, but from whatever dirt with the bacteria or spores that may be hanging on to the rusty item.

Once tetanus infection sets in, this results in severe uncontrollable muscle spasms, like lock jaw or whole body stiffening. The bacteria produce a toxin that affects the nerve synapses that cause muscles to continuously contract or go into spasm. The disease unless treated can be deadly.

Vaccine against tetanus is universally recommended and is widely available. It’s part of the childhood immunization in the DPT (Diptheria, Pertussis, Tetanus) vaccine.

So you can still develop tetanus from stepping on a non-rusty stainless nail, if contaminated with dirt. Unless you’re adequately vaccinated against tetanus.

Muscular spasms in a patient with tetanus. Painting by Sir Charles Bell, 1809

3. Don’t sit too close to the TV, it can damage your eyes, or harm you.

I was told this by my parents when I was little. I just thought that we were not supposed to sit too close from the television as something might come out suddenly from the TV screen.

I know my parents meant well. However this warning is kind of outdated now. It’s not really an old wives’ tale, but rather as an old technology’s tale.

The old television set before the 1950-60’s emitted levels of radiation, that after repeated and prolonged exposure to them, can cause some harm. But with later models of television that were built with proper shielding, the levels of radiation exposure is negligible.

Now that the TV sets that use cathode ray tubes (those bulky sets we have those days) are obsolete, we really don’t have to worry about emitted radiation from TV anymore. LCD and plasma TV don’t emit x-radiation at all.

Too much TV watching can still cause eyestrain though. Plus for young kids, there’s more fun things to do than watch TV.

4. Don’t crack or pop your knuckles, for this will cause arthritis.

According to one report, 20-50% of people, crack their knuckles. Many do it as a nervous habit. If you’re one of them, you probably have heard somebody warned you to stop, or else you will develop arthritis.

However there is no medical truth to this. And it’s not that it has not been studied. In one study, researchers look into more than 200 people, 20% of whom cracked their knuckles regularly. Of those knuckle crackers, 18.1% of them developed arthritis in their hands, compared to 21.5% of the study participants who did not crack their knuckles. So this study showed that development of arthritis is about the same, whether you crack your joints or not.

By the way, are you wondering what cause the popping sound?

When a finger or joint is extended like in an act of cracking your knuckles, the pressure inside the joint is lowered and the gases that are present in the synovial fluid, such as carbon dioxide, are released in the form of a bubble. This rapid implosion, collapse, or bursting of the gas bubbles creates an audible popping sound.

Even though knuckle-cracking has not been proven to cause arthritis, studies have shown that it’s not good either. In at least one study, chronic joint popping was shown to cause inflammation and weakened grip in the hands.

5. Don’t swallow chewing gum, for it can stick the insides of your intestines.

You probably heard this warning when you’re a child, or you told your kids this warning as well. Folklore suggests that it takes seven years for the gum to pass through the digestive system. However, there is no truth to this.

Certainly I have swallowed a few gum before, mostly not intentional but accidental. And obviously, nothing bad happened to me.

Though it’s true that the gum is indigestible, it’s not true that it will stick your insides, for it will pass through, with your stools within days, not years.

However there are rare reported cases of large amount of swallowed gum, combined with constipation, that caused blocked intestines in children. So I would still not advise to swallow your chewing gum. But if you accidentally swallow one, don’t sweat, it’s not that harmful.

Don’t scare your kids either that if they swallowed a watermelon seed, it will grow into a watermelon inside their stomach. Though if they are too young to understand how pregnancy happens, they might believe you that that’s from swallowing watermelon seed.