Top 10 Medical Myths

10) Myth: Fluoride in your drinking water and dental products is bad for you.

Reality: According to the American Dental Association, Cavities used to be a fact of life. But over the past few decades, tooth decay has been reduced dramatically. The key reason: fluoride. Research has shown that fluoride reduces cavities in both children and adults. It also helps repair the early stages of tooth decay even before the decay becomes visible. Unfortunately, many people continue to be misinformed about fluoride and fluoridation. Fluoride is like any other nutrient; it is safe and effective when used appropriately.

9) Myth: Drinking eight glasses of water a day is good for your overall health.

Reality: Everyone has heard that we should drink eight glasses of water a day, but there's no way to determine where this belief originated, nor has there ever been a scientific study to support it, explains Dr. Alex Finkbeiner, chairman of the UAMS Department of Urology. Interestingly, one of my colleagues also questioned whether such a statement was true and, after conducting a research study, concluded there is no basis for such a statement. I advise patients to simply let their thirst guide their fluid intake unless there is a specific medical reason to do differently.

8) Myth: Chewing gum takes seven years to pass through your digestive system.

Reality: The gum component itself is pretty indigestible, but will "pass" in a mass and will not stick your insides together. This one probably got going when exasperated parents tired of buying more gum after half an hour because their kids had chomped, then swallowed, their allotment.

7) Myth: The flu vaccine causes the flu.

Reality: You cannot catch the flu from a flu vaccine. Older vaccines were less pure and sometimes caused brief reactions, such a fever and chills. The newer flu vaccines contain only parts of the influenza virus used by the body to form an immune response.

6) Myth: You can actually throw your back out.

Reality: The fact is, you cannot throw your back out--it's a figure of speech. However, the experience of sudden, severe back pain is no myth to the person suffering through it. And it can certainly feel as though some major structures in the back have moved, or that to feel better, something must be returned to its original location.

5) Myth: It's dangerous to swim after eating.

Reality: This myth was disproved in the '60s but still gets trotted out. The very worst you can expect is a stitch (ie, a short, sharp pain in the side), in which case you should get out of the water.

4) Myth: Eating turkey causes drowsiness.

Reality: Turkey does contain tryptophan, but it makes us sleepy only if taken on an empty stomach without protein. Sleepiness after a Thanksgiving meal is probably instead caused by carb overload (mmm... mashed potatoes!) or alcohol consumption, or maybe a combination of both.

3) Myth: Cracking your knuckles will cause arthritis.

Reality: There is no evidence that cracking your knuckles inflames the joints and leads to arthritis. The cracking causes the bones to pull apart, forming a gas bubble and breaking the adhesive seal in the joint. About a quarter of the people in the US crack their knuckles and might begin to lose their grip a little; constant cracking can weaken the fingers.

2) Myth: Mobile phones cause brain cancer.

Reality: For radiation to cause cancer, it must break chemical bonds in the body. Only ionizing radiation can do this. Ultraviolet radiation, x-rays, and gamma rays are the culprits. Visible light and radio waves are always safe.

1) Myth: Wet hair in cold weather makes you sick.

Reality: Despite what your grandmother told you, blow-drying your hair when it's cold out will not help ward off illness. Whether or not you catch a cold depends on your immune system and what viruses or sick people you are exposed to. Interestingly enough, cold air can trigger a runny nose, not a cold, in many people; it's called vasomotor rhinitis.