Happy New Year, everyone! Welcome to 2008! I hope everyone had a good holiday.
I'm going to start the year off by telling you about 7 common medical myths out there. Aaron Carroll, a pediatrician at the Regenstrief Institute in Indianapolis, and Rachel Vreeman, a pediatrician at the Indiana University School of Medicine, recently published a letter in the British Medical Journal. In this letter, they outlined 7 myths that many people, including many doctors and other health professionals, believe. So let's take a look at these myths and debunk them, shall we?
1. People should drink at least 8 glasses of water a day
Nobody knows for certain where this common recommendation came from. However, it's not based on any hard scientific evidence.
We used to preach this recommendation in 20/20, but after reviewing the scientific evidence, we changed our recommendation to 6-8 glasses per day. Where did we come up with this recommendation? Well, the standard recommendation is 1 milliliter of water for every calorie of energy you expend each day. We estimated that the men in 20/20 are expending, on average, about 2,750 calories per day, and the women are expending about 2,450 calories per day. Thus, the water recommendation for men is 2,750 milliters per day, and it's 2,450 milliters for women. If we estimated that you get about 1,000 milliters of water from the food you eat, this leaves 1,750 milliters (about 7 glasses) for the men and 1,450 milliters (about 6 glasses) for women. There are also epidemiological studies that suggest that 6-8 cups are associated with a lower risk of bladder cancer and kidney stones. So, we set our recommendation at 6-8 cups. There is no need to exceed 8 cups, with the exception of frequent exercise in extremely hot and humid environments, where greater water intakes may sometimes be necessary.
2. We only use 10% of our brains
Here we have a case of communal reinforcement. People have been spouting this "fact" since 1907, and nobody has bothered to question it. Yet, numerous brain imaging studies show that no area of the brain is completely silent or inactive.
3. Hair and fingernails continue to grow after death
Sounds creepy, but it's not true. After death, your skin dries out and retracts, which gives the appearance that your fingernails and hair are growing. But they aren't. Hair and fingernail growth require complex hormonal regulation that stops after death.
4. Shaving hair causes it to grow back faster, darker, or coarser
Clinical studies have shown that shaving hair does not make it grow back faster, darker, or coarser. Like myth #3, it's all an illusion. Shaved hair lacks the finer taper seen at the ends of unshaven hair, giving the impression of coarseness. Also, the new hair has not been lightened by exposure to sun or other chemicals, giving it a darker appearance.
5. Reading in dim light ruins your eyesight
Every time I'm reading, my grandmother is alwasy telling me, "You need more light. You're going to ruin your eyes!" But there is no scientific evidence that this is true. While it can cause temporary eyestrain, there is no evidence that there is permanent change in the structure or function of the eyes.
6. Eating turkey makes people especially drowsy
People say this because turkey contains tryptophan, an amino acid that is involved in sleep and mood control, and can cause drowsiness. However, turkey does not contain an exceptional amount of tryptophan. In fact, it has no more tryptophan than other types of meat. Pork and cheese has more tryptophan than turkey! Also, the presence of other food at a holiday meal will slow the absorption of tryptophan. Finally, the presence of other amino acids in the meat will compete with tryptophan for crossing the blood-brain barrier.
The reason you become sleepy after a holiday meal is because large meals decrease blood flow and oxygenation to the brain. That glass of wine that you had with dinner may also have something to do with your drowsiness.
7. Mobile phones create dangerous electromagnetic interference in hospitals
This one is more controversial, but there is not one reported case of a death caused by the use of a cell phone in a hospital. There have been occasional reports of things like incorrect readings on cardiac monitors or false alarms. In a study out of the Mayo Clinic in 2005, researchers did 510 tests with 16 medical devices and 6 cell phones. They found the incidence of clinically important interference was only 1.2%. Other studies have had similar results, showing minimal interference that only occurs when cell phones are used in less than 1 meter from equipment. Other studies have found no interference when cell phones were used in a "normal way". So, while there is some evidence that cell phones can create some weak interference in some instances, there's no evidence they are dangerous when used in a normal way in a hosptial setting. Despite this myth, many hospitals have banned the use of cell phones.
So there you have it. So the next time someone tells you that you only use 10% of your brain, ask them where the other 90% went :)