Does the rhythm method work? Do microwaves destroy nutrients in food? Does sitting close to a TV ruin your eyes? Should you pee on a bluebottle sting?
Last week, I began a series aimed at debunking common household myths. Since I’ve collected dozens of them, it seems more efficient to do them 10 at a time than one by one.
Let’s dive right in.
- Urine treats bluebottle stings
The bluebottle, also known as the Portguese Man o’ War, is a common sight on South Africa’s beaches.
Related to jellyfish, their biology is weird, but what they have in common with jellyfish is that their tentacles contain barbs or stingers that can be ejected to deliver a potent venom to prey.
If you’ve ever come into contact with them, you’ll know all about it. It is surprisingly painful and the pain can last surprisingly long. It is rarely dangerous, and then only in extreme circumstances, such as being covered in tentacles, or if the victim exhibits an allergic reaction.
(If you were stung by a box jellyfish instead of the far more common bluebottle, seek immediate medical attention. You’ll need antivenom and supportive treatment in hospital.)
A common home remedy to relieve the burning pain of a bluebottle sting is to urinate on it. The same is sometimes said for bee stings and wasp stings. Allegedly, something in the urine neutralises the venom and relieves the pain and inflammation.
The origin of this belief comes from the fact that vinegar, or acetic acid, sometimes offers relief. Urine contains uric acid, which is believed to be equally effective.
Writes Lisa-ann Gershwin, a researcher at Australia’s Commonwealth Scientific and Industrial Research Organisation: “Vinegar works well to inhibit stinging cell discharge in box jellies and Irukandjis, and in some bluebottles, but in others it actually stimulates discharge. For this reason it is not recommended for confirmed bluebottle stings.”
So, what about urine?
“To make things more complicated, urine can be either acidic or alkaline,” she writes. “For species neutralised by vinegar, urine is only about 25% as effective if acidic, and it may stimulate discharge if alkaline.”
So it’s 50/50 whether acid works, it’s 50/50 whether urine is acidic, and even then, it’s only marginally effective.
The Mayo Clinic says not to do any of the following: scraping out stingers; rinsing with human urine; rinsing with cold, fresh water; applying meat tenderiser (which is usually based on vinegar); applying alcohol, ethanol or ammonia; rubbing with a towel; or applying pressure bandages.
What you should do is carefully pluck off visible tentacles with fine tweezers, soak the skin in hot (but not scalding) water, and keep the affected skin immersed or in a hot shower until the pain eases. Afterwards, apply 0.5% to 1% hydrocortisone cream or ointment twice a day to the affected skin.
In serious cases, treatment might include oral antihistamines or corticosteroids, and pain killers.
Unless you have any of those in your urine, don’t drop your rods and ride to the rescue in flagrante delicto.
2. The rhythm method
In 1930, Pope Pius XI declared contraception anathema in a Christian marriage. Subsequent papal encyclicals reconfirmed the prohibition on the use of any and all interference with natural conception, from condoms up to and including surgical sterilisation, in-vitro fertilisation and abortion.
Some conservative Protestant churches likewise preach what they call “natural family planning”, while a few veer madly into “quiverfull” territory, encouraging married women to have as many children as possible.
Other religions are generally more liberal about contraception.
“Natural family planning” relies on the “rhythm method”, which recognises that women ovulate in the middle of their menstrual cycle. By meticulously keeping track of the onset of menstruation, they can determine their time of ovulation. The egg typically remains viable for only about a day, but since sperm can remain alive in the uterus for as many as five days, the rhythm method involves abstaining from intercourse for five or six days before until three days after ovulation.
Practising the rhythm method correctly “requires careful record keeping and persistence”.
In an ideal world, the rhythm method can work well, but in practice, as many as 15% of women who practice natural family planning still become pregnant in the first year. (Although this source says it’s 24%, and this one says it’s 25%.)
To be fair, male condoms aren’t great at preventing pregnancy either. With correct use, they have a failure rate of only 2%, but in practice, 13% of couples using them unintentionally get pregnant. Female condoms perform worse.
Oral contraceptives for women are better, but suffer from a similar problem. With correct use, they reduce the risk of pregnancy to 0.3%, but as actually used in the real world, they fail 7% of the time.
Injectable contraception roughly halves both the correct use and real-world failure rate of oral hormonal contraceptives.
Hormonal implants, intra-uterine devices and male or female sterilisation are the only contraceptive methods that can reliably reduce the risk of pregnancy to well below 1%. In the absence of these methods, the best advice is to combine at least two prophylactic methods, such as the pill and a condom.
The rhythm method is one of the worst ways to avoid pregnancy, and like the pull-out method, does nothing against sexually transmitted infections, either.
3. Cracking your knuckles causes arthritis
If you’re a habitual knuckle-cracker, you’ve probably been told to cut it out because it will cause arthritis.
The popping sound you hear when knuckles are bent backwards is caused by bubbles that form and collapse in the synovial fluid, which lubricates joints. While it has been compared to cavitation, which can erode steel ship propellers, there is no evidence that it can cause any permanent injury to the tissues in your joints.
You can, of course, injure yourself if you bend your knuckles too far, and excessive wear and tear can cause osteoarthritis, which is the degradation of cartilage in the joint, but neither of these is related to the popping you hear when cracking your knuckles.
The real reason you should cut it out is that it’s annoying your parents.
4. Microwaving food is bad for you
We all know someone who calls microwaves “cancer boxes”. This is mostly because they lack the physics education to distinguish between electromagnetic radiation and ionising (nuclear) radiation. Microwaves aren’t gamma rays.
(Even gamma rays don’t make food radioactive. Irradiating food as a hygiene measure is beneficial and entirely harmless.)
Another factor that influences this sort of belief is simple technophobia. Many people have an instinctive feeling that traditional practices are somehow better or more authentic than new-fangled methods. They’re wrong. How good or bad a practice is has nothing to do with how modern or traditional it is.
Microwaves work by affecting molecules that have a polarity. The water molecule is the most common of these electrically asymmetrical molecules, but many acids, ethanol and sucrose will also respond to microwaves by vibrating and building up heat energy.
But doesn’t it destroy nutrients? Sure it does, but so does conventional cooking.
Let’s defer to the scientists: “The cooking method that best retains nutrients is one that cooks quickly, heats food for the shortest amount of time, and uses as little liquid as possible. Microwaving meets those criteria. Using the microwave with a small amount of water essentially steams food from the inside out. That keeps in more vitamins and minerals than almost any other cooking method and shows microwave food can indeed be healthy.”
There certainly are reasons why some foods cook better, or taste better, when cooked in an oven or a pan, but many foods – like potatoes, vegetables and soups – can be cooked more efficiently, more quickly, more cheaply, and more nutritiously in a microwave oven.
5. Swallowed chewing gum stays in your body for seven years
I recall being told that I should never swallow chewing gum, because it would get stuck in my tummy and stay there for seven years, blocking up the works.
In reality, chewing gum will do nothing bad to you. “[G]um is pretty immune to the digestive process,” pediatric gastroenterologist David Milov of the Nemours Children’s Clinic in Orlando, Florida, told Yale Scientific. “It probably passes through slower than most foodstuffs, but eventually the normal housekeeping waves in the digestive tract will sort of push it through, and it will come out pretty unmolested.”
That said, there are rare cases where excessive ingestion of chewing gum has caused intestinal or oesophageal obstructions in children, so it’s probably wise to recommend against it. And that said, if you’re giving your children so much chewing gum that their swallowing it can cause obstructions, you should probably revisit your parenting strategy.
6. Coffee stunts your growth
It is a common belief that coffee stunts growth in children, because coffee causes osteoporosis.
According to the Harvard Medical School, that coffee can cause osteoporosis was a speculative belief in the medical literature many years ago, based on the observation that caffeine can increase the body’s elimination of calcium, and lack of calcium can contribute to osteoporosis.
However, the calcium excretion effect is small, and further analysis showed that the apparent link with osteoporosis had more to do with the fact that coffee drinkers tend to drink less milk. Coffee has nothing to do with it.
Coffee is one of the most researched substances on Earth, and in moderate quantities (up to five cups per day) has not been linked to any significant ill effects. On the contrary, it has been linked with reduced risks for Type 2 diabetes, abnormal heart rhythms, stroke, Parkinson’s disease, Alzheimer’s disease, liver disease, certain cancers (especially liver cancer), and gout.
Of course, those links also may have nothing to do with coffee per se. For example, people who don’t drink alcohol are likely to drink coffee instead, and therefore the lower alcohol intake will benefit the liver.
There is no evidence that coffee stunts growth in children, and conversely, no evidence that abstaining from coffee will make you grow taller.
Coffee is generally disrecommended for children, due to its caffeine content, but even this isn’t a hard and fast rule. According to Johns Hopkins University, Canada has set guidelines for daily caffeine consumption for children that recommend no more than half a cup for kids between four and six, and one cup for those between 10 and 12 (with pro rata doses for other ages).
It should be noted that this goes for caffeine, not coffee alone, so tea, soft drinks, energy drinks, and even chocolate candy and hot chocolate, should be counted.
7. Fresh vegetables are better than frozen vegetables
The correct answer to whether fresh or frozen vegetables are more nutritious is: it depends.
If your fresh vegetables are truly fresh, because you grew them yourself or you bought them at a local farmer’s market, they’ll be great.
A lot of “fresh” vegetables are far older than a day or so, however, and as they get older, nutrients tend to break down. By the time you find them on your supermarket shelves, they might have spent a week in transit.
Frozen vegetables are frozen very soon after harvesting, and often in peak season, too. That means that nutrients are sealed in until you defrost and cook them. There may be textural reasons to prefer non-frozen foods, but they’re not worse than fresh food from a nutrition standpoint.
A similar argument can be made for some canned produce, although they often contain added salt, or even sugar.
In some cases, the canned produce is even better than the fresh equivalent, according to Beth Czerwony, a registered dietician (remember, that’s the protected title, as opposed to “nutritionist”, which anyone can use).
“Canned tomatoes have been heated, and that increases the amount of lycopene in them that the body can absorb, which is good for eye health,” she wrote.
8. Shaving hair makes it thicker
People often recommend against shaving hair because it supposedly grows back thicker.
This is false. A shaved hair feels thicker when it grows back because it has a blunt tip. If you let it grow, the tip will wear thinner, and the hair will feel softer. The hair, as it grows from the base, has exactly the same diameter as before it was shaved, and no amount of shaving will make that diameter thicker.
9. Sitting too close to a TV or other screen ruins your eyes
We were all brought up with the admonition not to sit too close to the television, because it would ruin our eyes. Back in the day of cathode ray tubes, the belief that electromagnetic radiation close to the screen could cause harm reinforced this belief.
The latter concern is likely false, but is in any case moot nowadays.
The former concern is also false, however, as might be suggested by the fact that we nowadays sit only a foot or two away from computer screens all day.
Paradoxically, the causality may in fact go the other way. Children who sit close to the television may be doing so because they are developing near-sightedness. It isn’t the television that’s bad for the eyes, it’s bad eyes that cause the preference for proximity.
Optometrist Dr. Jason E. Compton writes (with citations to the medical literature): “Digital eye strain, characterized by symptoms like dry eyes, itching, and headaches, is a condition that can arise from prolonged use of digital screens, including televisions. However, it’s crucial to note that these symptoms are temporary and do not lead to permanent eye damage.”
The eye strain comes from several facts. Prolonged focus at the same distance can strain the eye muscles, and when we watch screens, we often blink less, leading to dry eyes and that gritty, red feeling you get at the end of a long day.
There are several precautions you can take to reduce eye-strain associated with screen use, but sitting further away from the screen is not one of them.
10. Eating at night causes weight gain
Eh, sorry. I was wrong about this one.
“Eat breakfast like a king, lunch like a prince and dinner like a pauper,” wrote Adelle Davis, perhaps the most famous nutritionist of her age, in 1942.
That advice was also long dismissed by experts, on the basis that weight gain is largely a function of eating more calories than you burn.
“In fact, studies in humans indicate that it’s not necessarily the time you eat, but how much you eat that matters,” says Healthline, citing papers that suggest it is more about calorie intake than timing.
They found that in children, eating after 8pm wasn’t associated with increased caloric intake, and nor was it associated with weight gain. In adults, however, they found that food eating after 8pm did increase total caloric intake, therefore explaining the observation of weight gain in people who eat late at night.
However, recent research in humans suggests that time of day does matter. The research was limited to 16 participants who were already obese, but found that eating later, without varying total caloric intake, affects how the body stores fat and regulates appetite hormones.
So, it appears shifting your dietary intake a few hours earlier in the day might, in fact, prevent or reduce weight gain. It looks like Davis might have been right after all.
“The science”
That last one raises an important point. There’s no such thing as “the science”. Science isn’t a monolithic entity, or an unvarying authority. Science is a method. It’s a process.
Even the best scientific knowledge of today can be improved, or even invalidated, tomorrow. A surprising amount of scientific knowledge is, frankly, not very good.
Reams have been written, for example, about the replication crisis in science: many experimental findings that have been published and peer reviewed are hard or impossible to reproduce, casting grave doubt upon their validity.
This is especially true in the behavioural, cognitive, and social sciences, but also in complex (and highly competitive) natural science fields such as medicine and diet. Cancer research is one of the worst-affected areas.
Whenever you’re unsure about something, it is always worth checking the latest scientific literature. However, don’t take a solitary result as the be-all and end-all.
That’s how newspapers generate the sensational headlines that give birth to all their stories that this or that “has been linked to” cancer, or that a cure for some or other cancer is now just a matter of time and money.
That’s how the media generates half of these household myths.
Only by reading widely, and understanding a little about what makes good science, can one avoid the ever-present myths and legends that constitute “folk wisdom”.
[Image: The bluebottle, also known as the Portuguese Man of War, often washes up on South African beaches. Photo by Flickr user Roger Allison-Jones, 2006. Used under CC BY-NC-SA 2.0 licence]
The views of the writer are not necessarily the views of the Daily Friend or the IRR.
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