Wednesday, July 23, 2014

6 Common Science Myths Debunked

My sister and I recently saw a preview for the new Scarlett Johansson movie, about a woman who becomes superhuman when she is able to access the 90% of her brain that is unused in all other humans.  I scoffed at that old myth, but my sister wasn't convinced that it is a myth.  This gave me the idea to look at some pervasive myths in science and medicine, and try to debunk them.  Here are the top 6 (started out as 5, but the cell phone one was too hard to resist) science myths many people have accepted as fact.

1. We humans only use 10% of our brains
Scarlett Johansson is lying to you (or at least Luc Besson is).  The idea that being able to access 100% of your brain would make you superhuman is completely untrue - because we already do access 100% of our brains.  Different regions of the brain are used for different functions, like moving your muscles, controlling your heartbeat, hearing, seeing, etc.  Much of what the brain does is outside of conscious thought, and so it is possible that that's why people think we only use 10% of our brains.  But if the 10% myth were true, strokes and brain injuries would not have such drastic effects.  It just doesn't make evolutionary sense to not be using 90% of our giant brains.  Think about it, the evolution of such a large brain came at a high cost.  It made live birth far more dangerous for our female ancestors, because anyone with a pelvic bone that was too small risked the infant being stuck and both dying.  On top of that, recent work with guppies has found an increase in brain size is met with a decrease in reproductive rate and the size of internal organs.  Why would we put up with such potentially devastating trade-offs if we were not using our giant brains to their full extent?

2. Deodorant causes breast cancer
This one is pretty old; I remember hearing about it in elementary school (along with underwire bras causing cancer).  The idea is that potentially carcinogenic chemicals were absorbed in the skin through razor nicks, and accumulated in lymph nodes.  The body couldn't get rid of the toxins because the antiperspirant keeps you from sweating in that area, and this caused cells to mutate, leading to breast cancer.  This was supported by a fairly badly designed study that found that women who were diagnosed with breast cancer earlier also started shaving their underarms and wearing antiperspirant earlier - though they did not include a control group of women without breast cancer.  There is no evidence that deodorant causes breast cancer.  First of all, lymph nodes wouldn't secrete any absorbed toxins because they aren't connected to sweat glands at all.  Second, the whole point of the lymphatic system is to sequester and filter potential infections and toxins, and then transporting these to the liver and kidneys to be cleaned up and/or disposed of.  Third, the lymphatic system is part of the circulatory system, so anything absorbed in the lymph nodes around your underarms would actually transported to other parts of your body - that means that if your underarm lymph nodes did, in fact, absorb "toxins" from your antiperspirant, they could be "secreted" elsewhere on your body.  And most importantly, a large epidemiological study published in 2002 looked at the possible link between deodorant use and breast cancer, and found no evidence that antiperspirant use leads to cancer.  Aluminum is the main ingredient in antiperspirants, it blocks the sweat glands to keep you from sweating from your underarms.  Breast cancer tissue does not contain more aluminum and normal breast tissue.  Some people assume that not sweating from your underarms is really awful because it keeps you from being able to sweat out other toxins or from cooling yourself.  But remember, humans have sweat glands all over our bodies, not just in our underarms.

3. Microwaves alter food chemistry, which could kill you
electromagnetic spectrumThe first time I heard of this idea, I was apoplectic.  This is one of the most ridiculous things I've ever heard in my life, and I'm sorry if you believe it and I've insulted you, but COME ON!  Microwaves are invisible, low energy waves that are composed of photons (the same way visible light is).  But in microwaves, the energy of these photons is so low that they can't cause chemical changes in the molecules they encounter.  Microwaves have a slightly smaller wavelength than radio waves, but longer than the waves of visible light.  The reason why radiation from UV, X, and gamma rays is bad for you is because those wavelengths are small enough to mess with your DNA.  But the wavelength of microwaves is too big to cause any kind of damage, to your DNA if you stand in front of it and to the chemical composition of your food.  The molecules in the food will absorb the energy from the microwaves, which is what heats up the food; obviously, heating food to a very high heat can cause carbohydrates and proteins to hydrolyze, and it can degrade certain vitamins.  But these things also happen when heating up food in an oven - it's the HEAT caused by the energy in the microwaves that are having the effect, not the waves themselves.  (source)

4. Taking vitamin C will keep you from getting sick
When I was in my last year of high school, I went on a school trip that people typically came back from sick as dogs.  My friends and I had an idea - one of us would take vitamin C, one would take cold meds, and I would drink V8 - and we would see who got better faster.  Of course, I had sinusitis and bronchitis, but still... What does the real science say?  Vitamin C doesn't really do much in terms of preventing or treating colds.  Even when taken regularly prior to sickness, it doesn't do much.  Taking vitamin C can boost your immune system, but it doesn't do anything to specifically help your immune system fight off infection from the viruses that cause colds.  The common cold is caused by a virus, which is why it's so difficult to cure. 
Can we get a wut wut for chemophobia?

5. Fluoride in drinking water will kill you
Fluoride is naturally found in soil, water, and some foods, naturally.  Municipal water supplies are often fortified with fluoride to promote dental health, and basically to mimic what nature does in places where nature may not be doing it enough.  Tooth enamel is made of hydroxyapatite, which can be dissolved in acidic conditions.  Water fluoridation uses a compound called fluorapatite, which is hydroxyapatite with fluoride ions instead of hydroxyl ions.  Fluorapatite is stronger and more resistant to acidic conditions than hydroxyapatite, and so it greatly reduces the rate of cavity formation.  When fluoride is added to drinking water, it's usually at a safe and low concentration (0.7 to 0.8 ppm).  Those (developed) countries that do not fluoridate their water instead provide fluoride tablets or fluoride-fortified milk to their citizens.  Systematic reviews have found no adverse negative effects from normal levels of fluoridation.  Fluorosis is what people are afraid of when they think of fluoridated water.  But fluorosis is the result of extensive exposure to fluoride (10-20 mg per day for 20 years) - levels that are not present in drinking water (you might get 1 mg of fluoride per litre of water, so most people will be getting 2-3 mg per day).  There has been no scientifically proven link between water fluoridation and cancer, Down Syndrome, lowered IQ (only happens when exposed to HIGH levels of fluoride, not the low levels in our drinking water), or any other health problem.  Water fluoridation is a public health win, reducing oral disease and tooth decay by up to 40%.

6. Your cell phone is trying to kill you
Everyone has seen that video of a bunch of teenagers popping corn kernels using their cell phones, right?  The assumption was that cell phones produce microwaves that fry your brain or can cause infertility (from carrying them in your pocket).  Here's the thing though: if your cell phone was emitting microwaves high enough to fry your brain, it would also heat up the water particles on and in your skin, so just holding your cell phone would hurt like hell.  But, physicists have weight in and have said that this is actually physically impossible.  The phones are receiving a signal, not transmitting them, so any popping would not actually be caused by the cell phone itself.  And while it is possible to heat up an object using sound waves, the sound waves emitted by your phone are so low, that you have as much of a chance of getting popcorn to pop by yelling at it than by using your cell phone.  The more likely culprit?  Physics professor and author Louis Bloomfield says it's more likely a hot plate under the table.  While this was addressed when it first came up in 2008, I thought it still warranted a spot on my list.

No comments:

Post a Comment