Today's set of myths comes courtesy of my teenage daughter, and her friends Emma, Grace and Hannah. When her friends discover I'm a doctor, the questions come fast and furious. Sometimes I field medical questions, such as "Why does my knee hurt?" More often, the questions involve folklore and rumor.
My daughter and her friends came up with five questions for my consideration. They are good examples of the nature of medical myths because they:
- Are not easy to disprove
- Involve some "risky" activity (such as sneezing or chewing gum) that nearly everyone does relatively often
- Play on fear, such as the risk of developing cancer or dementia
- Have some component of believability; in fact, many medical myths are at least partly true.
Lily: Is it normal for a 6th grader — referring to one of the friend's little sisters — to weigh 15 times her birth weight?
I had to look up the answer to this one. I went to the growth charts, which provide a measure of average height and weight among healthy children. The average baby girl born in the United States is about 7¾ pounds. The average weight of a 12 year old is about 90 lbs. So, the "average" 6th grade girl weighs about 12 times her birth weight. Considering the significant variability in normal height and weight during development, there are many healthy 12 year olds who indeed weigh 15 times their birth weight.
Back to top
Emma: Can you get an ulcer from chewing gum?
I couldn't find any studies specifically addressing whether chewing gum could cause stomach ulcers. But there's no reason to believe it's true. Nearly all ulcers are now thought to be due to a bacterial infection (called H. Pylori) or medications (especially non-steroidal anti-inflammatory drugs, or NSAIDs, such as ibuprofen). Chewing gum has no connection to either of these. Well, almost no connection. There are aspirin-containing gums (such as Aspergum) that can cause ulcers just as aspirin tablets, ibuprofen and other NSAIDs can — and there's even a gum that may prevent ulcers. The leaves of Pistacia lentiscus (or Mastic tree), a native of the Mediterranean region, contain a resin which can kill H. pylori. Chewing mastic gum may be helpful in reducing the risk of ulcers. However, for the average teenager chewing "regular" gum, there's no clear increased risk of stomach ulcers. The bigger risk is probably getting in trouble for chewing gum at school.
Grace: Will you die if you sneeze with your eyes open?
Sneezing is actually a complicated reflex in which a trigger (such as pepper or dust) starts a chain reaction of events leading to the violent expulsion of the triggering substance. This reflex includes the muscles of the face and eyelids which briefly close the eyes. So, while it may take great concentration and may be difficult, keeping your eyes open during a sneeze is possible. But, it's certainly not fatal. Prove it yourself (if you dare).
Hannah: Do you lose brain cells just from tapping your forehead?
Many myths involve brain function and loss of brain cells. It's not possible to count brain cells until a person dies. So, claims about activities leading to the immediate loss of brain cells are largely unfounded. In fact, some studies have found no loss of brain cells with age, a surprising fact that was long considered impossible. Of course, there are other ways that brains may function poorly without losing brain cells. For example, brain injury or aging may disrupt connections between brain cells or alter the chemical messengers that allow the brain to function normally. This causes significant problems, even if the number of brain cells remains the same.
The idea that simply tapping the forehead may cause loss of brain cells is an illogical extension of something true. Severe or significant repetitive brain injury can lead to brain damage. A good example is a disease called dementia pugilistica that can affect boxers. Muhammad Ali has a form of this disease, called Pugilistic Parkinson's syndrome. That's why athletes are discouraged from high impact activities if they've suffered one or more concussions. But, it's highly unlikely (and no evidence support it) that tapping the forehead causes loss of brain cells.
Molly: Does deodorant cause breast cancer?
The rumor that deodorants or antiperspirants might cause breast cancer has been around for years. And it might seem logical. Perhaps chemicals in these products get into breast tissue through nicks or cuts from underarm shaving.
There's actually some good scientific evidence on this topic. Large studies comparing women with and without breast cancer suggest no definite connection between the disease and antiperspirant, deodorant use or underarm shaving. A smaller study did find a younger age at diagnosis among breast cancer survivors who shaved their underarms often, used antiperspirants or deodorants often and who did so at an early age. But this study only included women who had already been diagnosed with breast cancer. This type of evidence is considered weak and you can't draw any firm conclusions from it about the cause of breast cancer. While additional research might come to a different conclusion, for now it seems that most cancer experts dismiss the connection between breast cancer and deodorants.
The Bottom Line
I encourage my daughter and her friends to keep the questions coming. In my view, the only way to understand the difference between medical fact and myth is to keep asking questions and to keep an open mind. It's always important to consider the source of medical information, since much of it can come from unreliable sources.
The answers I give my daughter and her friends could change over time. But the need to maintain a healthy dose of skepticism never will.
Back to top
Robert H. Shmerling, M.D. is associate physician at Beth Israel Deaconess Medical Center and associate professor at Harvard Medical School. He has been a practicing rheumatologist for over 20 years at Beth Israel Deaconess Medical Center. He is an active teacher in the Internal Medicine Residency Program, serving as the Robinson Firm Chief. He is also a teacher in the Rheumatology Fellowship Program.