10 Old Wives' Tales About Your Health

Cats have been seen alternately as divine (the Egyptian goddess Bastet took a feline form) or evil (we all know black cats bring bad luck, right?). If the myth that cats steal sleeping babies' breath were true, it would definitely fit in with that darker image.

However, no scientific study or verifiable accounts back up such stories. Cats do crave softness and warmth. It's an instinct that keeps them close to the safety of their mothers as kittens. And some people suggest that the smell of milk on a baby's breath might further draw a cat toward the infant's mouth, resulting in accidental suffocation. However, many cats are indifferent to milk after they're weaned. Most adult cats, in fact, are lactose intolerant -- which won't stop all cats from accepting dairy treats, but should give you second thoughts about offering them.

Cats' supposedly murderous ways have also been blamed on feline feelings of sibling rivalry: Kitty resents all the attention lavished on a new baby. It's true that cats can be disturbed by major disruptions to their lives, but they usually act out by urine marking -- spraying or urinating outside the litter box -- or becoming more vocal, not by plotting revenge.

How did this myth start? It's possible that cats have inadvertently contributed to Sudden Infant Death Syndrome, or SIDS, in which an infant dies while sleeping for no known reason. Infants with respiratory conditions or an underdeveloped wake-response reflex are known to be at greater risk of SIDS. If such a child rolled toward a cat in his sleep, or if a cat stretched a paw on the baby's face, it might impair breathing enough to cause death. Then again, the cat's presence may have been pure coincidence.

Masturbation has long been condemned on moral grounds in Western society, going back to Biblical times. The Talmud forbids it as a waste of the gift of fertility. The influential eighteenth-century philosopher Immanuel Kant wrote that in masturbating, "a man ... degrades himself below the level of animals."

Given that reputation, it's no surprise that masturbation should be blamed for physical decay as well. In fact, if all of the dire consequences threatened were true, there would be a lot of blind, insane, sterile people with hairy palms and acne walking around.

We can't speak to the spiritual or metaphysical effects. However, we can say that masturbation has been as thoroughly researched as any topic in sexuality (and that's saying a lot), and no connection to the physiological effects has been proven. The truth is that masturbation is a normal part of sexual development. It's how children learn about their own sexuality, and how adults learn about arousal and pleasure, both alone or with a partner. Some evidence even suggests that in older men, at least, masturbation reduces the risk of prostate cancer.

The snap, crackle and pop of cracking knuckles really annoys some people. But is there a danger besides making a person unpopular among friends and coworkers?

Let's compare the knuckle-cracking process to the condition of arthritis. Joints are surrounded by a lubricating, nourishing soup called synovial fluid. This fluid contains fats, nutrients to maintain bone health and dissolved gases. Cracking the knuckles stretches the capsule that surrounds the fluid, and stretching the capsule increases its volume, which lessens the pressure inside. The gases expand under this lower pressure, forming bubbles that eventually pop. Fortunately for knuckle-cracking haters, it takes a while for the gases to reenter the solution, during which time the characteristic noises can't be made.

Arthritis -- specifically osteoarthritis -- is the degeneration of cartilage, which is the spongy cushion between bones in a joint. The exact cause isn't known, but injury, repetitive motion, genetics and increased stress on the joints from excessive weight are contributing factors. In theory, straining or breaking a knuckle while cracking it might put you at risk for arthritis, but no study has ever linked cracking knuckles directly with the disease.

Knuckles and other joints may also crack spontaneously due to natural changes in the ligament path over the bones. Cracking accompanied by pain, however, can signify other inflammatory conditions, including tendinitis and bursitis.

Chocolate lovers, rejoice: No studies have shown a direct link between the "food of the gods" (the original Greek meaning behind chocolate's scientific name, Theobroma cacao) and acne. But before diving into that pan of chocolate-fudge brownies, you should know the whole story.

Acne is caused by a strain of bacteria, scientifically known as acne vulgaris. The bacteria can breed in skin pores and hair follicles that become clogged with dirt, excess oils and dead skin cells. A buildup of acne vulgaris can irritate the skin, resulting in whiteheads, blackheads and pimples -- not-so-scientifically known as zits.

But the plot thickens. Acne can be aggravated by many factors that vary from person to person. Common triggers include hormonal surges, environmental pollutants, cosmetics and stress. Some foods also worsen outbreaks in some people, including dairy products and high-glycemic foods (those that make blood sugar levels spike). Some very popular types of chocolate fit both categories.

The problem with trying to pinpoint chocolate, or any factor, as the cause of any one case of acne is that other factors may also be contributors. Suppose you feel stressed about having acne. You eat chocolate to cheer yourself and suffer a flare-up. Was it the stress? The chocolate? Both, or neither one?

To be on the safe side, if you have acne and love chocolate, choose dark chocolate. Made with up to 80 percent cacao, it has more pure chocolate bliss and less sugar and dairy than milk chocolate or semi-sweet chocolate have.

You can trace this partial truth to experiments conducted in the Arctic by the United States military in the 1950s. Volunteers were adequately dressed from the shoulders down, but left bareheaded. Not surprisingly, that's where most of their body heat escaped -- up to 80 of percent of the body heat they lost, according to the earliest reports. The warning that you can lose 40 to 45 percent of your body heat from an exposed head became standard in the "U.S. Army Survival Manual." The reasons given are the lack of insulating fat and the proximity of the blood vessels to the surface.

Subsequent research conducted in Army labs qualify that claim. In a body at rest, 7 to 10 percent of heat loss occurs through the head. Engaging in work or exercise increases the body's core temperature and the flow of blood to the brain. So initially, you do lose more heat through the head -- up to 50 percent, similar to what the Survival Manual says. As the activity continues, however, the blood vessels near the skin in the rest of the body dilate, allowing more blood to flow throughout the body and reducing the flow to the brain. Meanwhile, the proximity of the vessels to the skin cools the blood to keep you from overheating. Heat loss through the head returns to about 7 percent.

It's still a good idea to cover the head in cold weather, of course, just like every other part of your body.

This old tale may be partly based on the medieval theory of humours. The idea was that good mental and physical health depended on the balance of four body fluids, called humours: black bile, yellow bile, blood and phlegm. A fever indicated an excess of blood, and the treatment included bleeding the patient -- which, in retrospect, was not such good advice. Fasting may have also been prescribed as a way to slow down what seemed to be an overcharged metabolism.

Likewise, every mucous mouthful a cold sufferer coughed up indicated an excess of phlegm. Phlegm was a wintry humour, associated with depressed spirits and depressed metabolism. The logical remedy was to stoke the bodily furnace with food, which would also lift the spirits. (This thinking may also underlie another myth: that you can "sweat out" a cold by bundling up, thus overheating the body.)

When you're sick with a cold or the flu, your body needs the nutrients of a balanced diet and energy from adequate calories to fight off the infection, especially in the early stages of illness. There's no medical advantage to undereating or overeating in either case. Staying well nourished and well hydrated is the best advice.

To the relief of eyeglass makers and their stockholders everywhere, eating carrots does not correct defective vision -- unless the vision problem is caused by a vitamin A deficiency. Vitamin A is essential to eye health. It's incorporated into the eye's photoreceptor cells, which capture light and allow you to see.

The human body can't produce Vitamin A. It must come from our diet, where it's available ready-made in meats, fish and especially liver. Although carrots don't supply vitamin A, they do contain a do-it-yourself version called beta-carotene. Beta-carotene is a chemical compound that gives a variety of vegetables their colorful hues, including leafy greens, orange squashes and red and yellow peppers. It's also a provitamin, from which the body synthesizes vitamin A.

With beta-carotene abundant in so many foods, how did carrots come to be named the miracle worker? In World War II, the British military wanted to explain their fighter pilots' remarkable success in shooting down German aircraft on nighttime raids. Coincidentally, the country had a bumper crop of carrots, which patriotic citizens planted in home gardens to increase domestic food supplies. Thus carrots became the Royal Air Force's secret weapon against German bombers. Wartime posters claimed that carrots "help you see in the blackout," referring to air raids, when cities went dark to avoid giving away strategic targets. Whether the propagandists knew it or not, German medical lore held the same belief.

The real reason for the Air Force's success? The military had developed an advanced system of airborne radar to detect enemy planes in the dark.

Like some other myths on our list, this one has enough semblance of truth to sound legitimate. Simple sugars are pure calories (i.e., energy). They're quickly digested and sent to the bloodstream. So a rush of energy in the blood should cause a rush of activity in the body. The evidence often cited is the typical scenario of kids at a party. They binge on cake, cookies and sugary drinks, and then play games and generally wreak (mostly harmless) havoc. Ergo, sugar causes their behavior.

The science of sugar metabolism tells a different story, however. When sugars enter the bloodstream, they're first sent to the muscles and internal organs for immediate use. Excess sugars are not "worked off." They're stored in the liver and muscles as glycogen for later use. Anything over storage capacity winds up as fat. At the party, it's excitement that inspires the kids' rambunctiousness; sugar just fuels it. A bored child may snack on donuts or sugar-laden cereal and then watch TV or play video games quietly.

Sugary snacks and sodas are rightly blamed for their role in obesity and tooth decay. But hyper behavior is one rap you can't pin on them -- unless, of course, they're caffeinated products like cola or chocolate. More about caffeine up next.

No studies have shown a direct cause-and-effect relationship between caffeine intake and stunted growth. However, the claim might not be totally unfounded. A supporting argument might go like this: Human growth hormone (HGH), which promotes proper development, is secreted mostly during sleep. Caffeine is a stimulant, which excites the nervous system and can interfere with sleep. Thus, consuming caffeine indirectly hinders the production of HGH and limits growth.

To repeat: This argument, while logical, lacks scientific backing. And when you consider the other factors that affect growth, including heredity and nutrition, you can see how simplistic the explanation sounds.

On the other hand, here's some food (or drink) for thought: Caffeinated beverages have increased in popularity. According to reports from the beverage industry, coffee sales rose 9 percent in 2010-2011, topping $4 billion worldwide, and sales of caffeine-laced energy drinks grew 136 percent between 2005 and 2009, mostly due to increased consumption by regular drinkers.

Yet people are, if anything, growing taller. Reports from the CDC indicate that the height of the average American guy rose about 1.5 inches between 1960 and 2002, and the typical female added 1 inch to her stature. And the average Australian has shown a similarly slow but steady growth. Again, many factors affected this trend. But if it should reverse and the average height drops following this boom in caffeine consumption, then this old wives' tale might warrant a closer look.

This "old" tale goes back only to 1970 and a book, "Vitamin C and the Common Cold," by Linus Pauling. Pauling was a brilliant chemist, a two-time Nobel Prize winner. In his book, he claimed that megadoses of vitamin C cured the common cold. This was a promising theory that Pauling had been investigating for several years. But he had no solid research to support it. The medical establishment loudly denounced him. The controversy proved to be great publicity, and many people bought into Pauling's claim -- and still do, despite the continued lack of evidence.

Don't write off the theory completely, however. In 2007, a sweeping review of 60 years of studies found that taking 200 milligrams of vitamin C every day (two to three times the recommended amount, but still a safe dose) reduced the time spent sick from a cold from about 12 to 11 days per year. It also seemed to cut the incidence of colds in people who were under extreme stress by 50 percent.

Marginal benefits, we agree. Yet in many ways, Pauling was ahead of his time. He believed that good health consisted of supplying the body with the proper balance of molecules needed for vital biochemical reactions. He named this approach orthomolecular medicine. Today researchers are excited about vitamin C because it's an antioxidant, a substance that repairs cells by rebuilding molecules that are damaged during everyday activities. The similarities between old wisdom and new research are enough to give us pause on this one.