Monday, May 30, 2011

List of common misconceptions Part V Health

The senses

An incorrectmap of the tongueshowing zones which taste bitter(1), sour (2), salty(3) and sweet (4). In reality, all zones can sense all tastes.
  • Different tastes can be detected on all parts of the tongue by taste buds,[118] with slightly increased sensitivities in different locations depending on the person, contrary to the popular belief that specific tastes only correspond to specific mapped sites on the tongue.[119] The original tongue map was based on a mistranslation of a 1901 German thesis[120] by Edwin Boring. In addition, there are not 4 but 5 primary tastes. In addition to bitter, sour, salty, and sweet, humans have taste receptors for umami, which is a savory or meaty taste.[121][122][123]
  • Humans have more than five senses. Although definitions vary, the actual number ranges from 9 to more than 20. In addition to sight, smell, taste, touch, andhearing, which were the senses identified by Aristotle, humans can sense balance and acceleration (equilibrioception), pain (nociception), body and limb position (proprioception or kinesthetic sense), and relative temperature (thermoception).[124] Other senses sometimes identified are the sense of time, itching, pressure, hunger, thirst, fullness of the stomach, need to urinate, need to defecate, and blood carbon dioxide levels.[125][126]

Skin and hair

  • Shaving does not cause terminal hair to grow back thicker or coarser or darker. This belief is because hair that has never been cut has a tapered end, whereas, after cutting, there is no taper. Thus, it appears thicker, and feels coarser due to the sharper, unworn edges. The fact that shorter hairs are "harder" (less flexible) than longer hairs also contributes to this effect.[127][128][129][130]
  • Hair and fingernails do not continue to grow after a person dies. Rather, the skin dries and shrinks away from the bases of hairs and nails, giving the appearance of growth.[131]
  • Hair care products cannot as such "repair" split ends and damaged hair. They can, however, prevent damage from occurring in the first place, smooth down the cuticle in a glue-like fashion so that it appears repaired, and generally make hair appear in better condition.[132][133][134][135][136]

Nutrition, food, and drink

  • Eight glasses of water a day are not necessary to maintain health.[137][138] Consuming things that contain water such as juice, tea, milk, fruits and vegetables also keeps a person hydrated.[138]
  • Sugar does not cause hyperactivity in children.[139][140] Double-blind trials have shown no difference in behavior between children given sugar-full or sugar-free diets, even in studies specifically looking at children with attention-deficit/hyperactivity disorder or those considered sensitive to sugar.[141]
  • Alcohol does not make one warmer.[142][143][144] The reason that alcoholic drinks create the sensation of warmth is that they cause blood vessels to dilate and stimulate nerve endings near the surface of the skin with an influx of warm blood. This can actually result in making the core body temperature lower, as it allows for easier heat exchange with a cold external environment.[145]
  • Alcohol does not kill brain cells.[146][147] Early temperance writers promoted the idea that drinking causes brain cells to die (as well as the assertion that the alcohol in the blood stream could cause people to catch fire and burn alive).[148] According to Queensland Brain Institute director Professor Perry Bartlett, there is no evidence that drinking alcohol leads directly to the death of brain cells.[146] New brain cells are generated on a daily basis.[146] Alcohol can however lead indirectly to the death of brain cells in two ways: (1) In chronic, heavy alcohol users whose brains have adapted to the effects of alcohol, abrupt cessation following heavy use can cause excitotoxicity leading to cellular death in multiple areas of the brain.[149] (2) In alcoholics who get most of their daily calories from alcohol, a deficiency of thiamine can produce Korsakoff's syndrome, which is associated with serious brain damage.[150]
  • A vegetarian or vegan diet can provide enough protein.[151][152][153] In fact, typical protein intakes of ovo-lacto vegetarians and of vegans meet and exceed requirements.[154] However, a strict vegan diet does require supplementation of Vitamin B-12 for optimal health.[151]

Human sexuality

  • A popular myth regarding human sexuality is that men think about sex every seven seconds. In reality, this has not been measured, and as far as researchers can tell, this statistic greatly exaggerates the frequency of sexual thoughts.[155][156][157]
  • Another popular myth is that having sex in the days leading up to a sporting event or contest is detrimental to performance. Numerous studies have shown that there is no physiological basis to this myth.[158] Additionally, it has been demonstrated that sex during the 24 hours prior to sports activity can elevate the levels of testosterone in males, which potentially could enhance their performance.[159]

The brain

Golgi-stained neurons in human hippocampal tissue. It is commonly believed that humans will not grow new brain cells, but research has shown that some neurons can reform in humans.


  • Those suffering from flu or cold congestion do not need to avoid dairy because it does not increase mucus production. Drinking milk and/or consuming other dairy products does not increase mucus production.[176][177]
  • Warts on human skin are caused by viruses that are unique to humans (human papillomavirus). Humans cannot catch warts from toads or other animals; the bumps on a toad are not warts.[178]
  • Frequently cracking ones knuckles or exercise in the absence of injury does not cause osteoarthritis.[179][180]


  • Waking sleepwalkers does not harm them. While it is true that a person may be confused or disoriented for a short time after awakening, this does not cause them further harm. In contrast, sleepwalkers may injure themselves if they trip over objects or lose their balance while sleepwalking. Such injuries are common among sleepwalkers.[181][182]
  • In South Korea, it is commonly believed that sleeping in a closed room with an electric fan running can be fatal. According to the Korean government, "In some cases, a fan turned on too long can cause death from suffocation, hypothermia, or fire from overheating." The Korea Consumer Protection Board issued a consumer safety alert recommending that electric fans be set on timers, direction changed and doors left open. Belief in fan death is common even among knowledgeable medical professionals in Korea. According to Yeon Dong-su, dean of Kwandong University's medical school, "If it is completely sealed, then in the current of an electric fan, the temperature can drop low enough to cause a person to die of hypothermia."[183][184][185][186] Although an air conditioner transfers heat from the air and cools it, a fan moves air to increase the evaporation of sweat. Due to energy losses andviscous dissipation, a fan will slowly heat a room.
  • Although it is commonly believed that most body heat is lost through a person's head, heat loss through the head is not more significant than other parts of the body when naked.[187][188] This may be a generalization of situations in which it is true, such as when the head is the only uncovered part of the body. For example, it has been shown that hats effectively prevent hypothermia in infants.[189]
  • Eating less than an hour before swimming does not increase the risk of experiencing muscle cramps or drowning. One study shows a correlation between alcohol consumption and drowning, but there is no evidence cited regarding stomach cramps or the consumption of food.[190]
  • Drowning is often thought to be a violent struggle, where the victim waves and calls for help.[191] In truth, drowning is often inconspicuous to onlookers. Raising the arms and vocalising are even usually impossible due to the instinctive drowning response.[191] Waving and yelling (known as "aquatic distress") is a sign of trouble, but not a dependable one: most victims demonstrating the instinctive drowning response do not show prior evidence of distress.[192]

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