Medical Myths

Cracking Your Knuckles Causes Arthritis
The knuckles are the joints between the fingers and hand, and these joints contain a lubricant called synovial fluid. When you crack your knuckles, you are pulling apart two bones at the joint, which means the synovial fluid has to fill more space. This decreases the pressure of the fluid, and dissolved gases that are present, such as nitrogen, float out of the area in tiny bubbles. The bursting of these bubbles is the familiar sound we hear when someone "cracks" his or her knuckles. This bubble-bursting is not the same as arthritis, which is when the body's immune system attacks joints. However, constant knuckle-cracking can injure joints and weaken fingers.

People should drink at least eight glasses of water a day
The advice to drink at least eight glasses of water a day can be found throughout the popular press.One origin may be a 1945 recommendation that stated: A suitable allowance of water for adults is 2.5 litres daily in most instances. An ordinary standard for diverse persons is 1 millilitre for each calorie of food. Most of this quantity is contained in prepared foods.w5 If the last, crucial sentence is ignored, the statement could be interpreted as instruction to drink eight glasses of water a day.
Another endorsement may have come from a prominent nutritionist, Frederick Stare, who once recommended, without references, the consumption “around 6 to 8 glasses per 24 hours,” which could be “in the form of coffee, tea, milk, soft drinks, beer, etc.”The complete lack of evidence supporting the recommendation to drink six to eight glasses of water a day is exhaustively catalogued in an invited review by Heinz Valtin in the American Journal of Physiology. Furthermore, existing studies suggest that adequate fluid intake is usually met through typical daily consumption of juice, milk, and even caffeinated drinks. In contrast, drinking excess amounts of water can be dangerous, resulting in water intoxication, hyponatraemia, and even death.

We use only 10% of our brains
The belief that we use only 10% of our brains has persisted for over a century, despite dramatic advances in neuroscience. In another extensive expert literature review, Barry Beyerstein provides a detailed account of the origins of this myth and the evidence disputing it. Some sources attribute this claim to Albert Einstein, but no such reference or statement by Einstein has ever been recorded. This myth arose as early as 1907, propagated by multiple sources advocating the power of self improvement and tapping into each person’s unrealised latent abilities.
Evidence from studies of brain damage, brain imaging, localisation of function, microstructural analysis, and metabolic studies show that people use much more than 10% of their brains. Studies of patients with brain injury suggest that damage to almost any area of the brain has specific and lasting effects on mental, vegetative, and behavioural capabilities.Numerous types of brain imaging studies show that no area of the brain is completely silent or inactive. The many functions of the brain are highly localised, with different tasks allocated to different anatomical regions.Detailed probing of the brain has failed to identify the “non-functioning” 90%.Even micro-level localisation, isolating the response of single neurones, reveals no gaps or inactive areas. Metabolic studies, tracking differential rates of cellular metabolism within the brain, reveal no dormant areas.

Hair and fingernails continue to grow after death
Morbid information about the body captures the imagination and reinforces medical mythology. In All Quiet on the Western Front, the author describes a friend’s fingernails growing in corkscrews after the burial.Johnny Carson even perpetuated this myth with his joke, “For three days after death hair and fingernails continue to grow, but phone calls taper off.” To quote the expert opinion of forensic anthropologist William Maples, “It is a powerful, disturbing image, but it is pure moonshine. No such thing occurs.”
This myth does have a basis in a biological phenomenon that can occur after death. As Maples and numerous dermatologists explain, dehydration of the body after death and drying or desiccation may lead to retraction of the skin around the hair or nails. The skin’s retraction can create an appearance of increased length or of greater prominence because of the optical illusion created by contrasting the shrunken soft tissues with the nails or hair. The actual growth of hair and nails, however, requires a complex hormonal regulation not sustained after death.

Shaving hair causes it to grow back faster, darker, or coarser
Another common belief is that shaving hair off will cause it to grow back in a darker or coarser form or to grow back faster. It is often reinforced by popular media sources and perhaps by people contemplating the quick appearance of stubble on their own body.
Strong scientific evidence disproves these claims. As early as 1928, a clinical trial showed that shaving had no effect on hair growth. More recent studies confirm that shaving does not affect the thickness or rate of hair regrowth. In addition, shaving removes the dead portion of hair, not the living section lying below the skin’s surface, so it is unlikely to affect the rate or type of growth. Shaved hair lacks the finer taper seen at the ends of unshaven hair, giving an impression of coarseness. Similarly, the new hair has not yet been lightened by the sun or other chemical exposures, resulting in an appearance that seems darker than existing hair.

Reading in dim light ruins your eyesight
The fearful idea that reading in dim light could ruin one’s eyesight probably has its origins in the physiological experience of eye strain. Suboptimal lighting can create a sensation of having difficulty in focusing. It also decreases the rate of blinking and leads to discomfort from drying, particularly in conditions of voluntary squinting. The important counterpoint is that these effects do not persist.
The majority consensus in ophthalmology, as outlined in a collection of educational material for patients, is that reading in dim light does not damage your eyes. Although it can cause eye strain with multiple temporary negative effects, it is unlikely to cause a permanent change on the function or structure of the eyes.Even in patients with Sjögren’s syndrome (an autoimmune disease that features inflammation in certain glands of the body), decreased functional visual acuity associated with strained reading improves when they stop reading.
One review article on myopia concludes that increased use of one’s eyes, such as reading in dim light or holding books too close to the face, could result in impaired ocular growth and refractive error.w36 The primary evidence cited was epidemiological evidence of the increased prevalence of myopia and the high incidence of myopia in people with more academic experience.The author notes that this hypothesis is just beginning to “gain scientific credence.” In the past reading conditions involved even less light, relying on candles or lanterns, so increased rates of myopia over the past several centuries does not necessarily support that dim reading conditions are to blame. In contrast to that review, hundreds of online expert opinions conclude that reading in low light does not hurt your eyes.

Chocolate and Fried Foods Give You Acne
Some speculate that this myth dates back to the baby-boom generation, who had worse acne than their parents and also more access to chocolate and fried foods. Wherever this idea came from, it's wrong. Pimples form when oil glands under the skin produce too much of a waxy oil called sebum, which the body uses to keep skin lubricated. But when excess sebum and dead skin cells block pores, that area of the skin gets irritated, swollen, and turns red -- the telltale signs of a pimple. It is unknown why sebaceous glands produce excess sebum, but hormones are the prime suspects, which explains why teenagers are affected more than others. Stress and heredity may also be factors, but chocolate bars and onion rings are off the hook.

Coffee Will Sober You Up
Some speculate that this myth dates back to the baby-boom generation, who had worse acne than their parents and also more access to chocolate and fried foods. Wherever this idea came from, it's wrong. Pimples form when oil glands under the skin produce too much of a waxy oil called sebum, which the body uses to keep skin lubricated. But when excess sebum and dead skin cells block pores, that area of the skin gets irritated, swollen, and turns red -- the telltale signs of a pimple. It is unknown why sebaceous glands produce excess sebum, but hormones are the prime suspects, which explains why teenagers are affected more than others. Stress and heredity may also be factors, but chocolate bars and onion rings are off the hook.
If you've had too much to drink, no amount of coffee, soda, water or anything else is going to sober you up. The only thing that will do the trick is time. The liver can metabolize only about one standard drink (12 ounces of beer, 6 ounces of wine, or 1.5 ounces of hard liquor) per hour, so if you're drinking more than that every 60 minutes, you'll have alcohol in your system for some time. The idea of coffee's sobering effect may have started because caffeine acts as a stimulant, counteracting the sedative effect of alcohol to a small degree. However, it has no effect on the amount of alcohol in the blood. So if you've been drinking, spend your money on a cab rather than a cappuccino.

Too Much Sugar Makes Kids Hyperactive
Many parents limit sugary foods, thinking they cause hyperactivity. It's right to restrict these treats, but the reasoning is wrong. These high-calorie foods offer little nutrition and can lead to obesity and other problems, but no scientific evidence says sugar causes hyperactivity. Sugar can provide a short-term energy boost, but that isn't the same as hyperactivity. The children at a birthday party acting like little tornadoes probably has more to do with the excitement of being around other kids, rather than the cake. And that unruly child in the grocery store throwing a fit with a sucker in his mouth and candy clutched in each fist? His parents probably haven't set appropriate behavior limits, and they most likely give him what he wants -- which is more candy.

You lose most of your body heat through your head
A military study many years ago tested the loss of temperature in soldiers when exposed to very cold temperatures. They found rapid heat loss in the head – and so the idea that we lose heat through our heads was born. But what they didn’t tell you was that the soldiers were fully clothed except for their heads. This obviously skews the statistics considerably. The fact is, completely naked, you lose approximately 10% of your body heat through the head – the other 90% is lost via the other parts of your body.

Teething causes a fever
Scientific studies have been done in the area of teething which show no correlation at all between fever and teething. If your baby is suffering from a new tooth and they also have a fever, it is advisable to check for other causes of the fever. The same is true of diarrhea which is also often blamed on teething in infants. It is always better to be safe than sorry when dealing with the health of children.

Back pain should be treated with bed rest
The opposite is actually true in this case. Bed rest can prevent the lower back from fully recovering – or at the very least, delay the recovery significantly. Patients who continue to engage in ordinary activities recover faster and usually have fewer problems with recurring pain and other back troubles. Interestingly, many studies have shown that this is not just true of back problems, but also many other medical problems. Thirty-nine independent studies found bed rest to be more harmful than good in a broad range of illnesses.

Eating at night makes you fat
Secret snackers rejoice! This is a complete myth. It doesn’t matter what time of day you eat, as long as you eat only the total calories that you burn each day, you will not gain weight. If you eat fewer calories than you burn, you will lose weight, and if you eat more calories, you will gain. It is as simple as that. Having said that, the routine of three meals a day at the same time each day can have other benefits in life (routine is good and it helps humans work more effectively), but snacks at night are no worse than snacks in the morning or afternoon.


It is harder to lose weight than to gain weight
Actually – once you get your head around a new eating pattern, math and science are working in your favor. It is mathematically easier to lose than to gain. For example, if you eat 3,500 calories more than you burn, you will gain 0.3 pounds (0.14 kg), but if you burn 3,500 calories more than you eat, you will lose 1 pound (0.45 kg). Also, if you want to lose weight, you can expose yourself to significant changes in temperature which speeds up your metabolism. Finally, the above information is based on a pure fat diet – variations to the math occur when you introduce other types of food.