Debunking Common Medical Myths

3. Myth: Cancer cannot be prevented.

Fact: As many as 50 percent or more of cancer deaths in the United States are caused by social and environmental conditions and unhealthy choices, according to the Centers for Disease Control and Prevention. In general, you can help your body prevent cancer if you quit smoking, avoid second-hand smoke, avoid drinking too much alcohol, avoid weight gain, eat five or more servings of fruits and vegetables a day, eat a low-fat diet and be physically active.

4. Myth: Shaved hair grows back faster, coarser and darker.

Fact: A 1928 clinical trial compared hair growth in shaved patches to growth in nonshaved patches. The hair that replaced the shaved hair was no darker or thicker, and did not grow in faster, according to Indiana University School of Medicine researchers who debunked seven commonly held medical beliefs in a 2007 report. When hair first comes in after being shaved, it grows with a blunt edge on top. Over time, the blunt edge gets worn so it may seem thicker than it actually is. Hair that's just emerging can be darker too, because it hasn't been bleached by the sun.

5. Myth: You should drink at least eight glasses of water a day.

Fact: A 1945 article from the National Research Council claimed that a "suitable allowance" of water for adults is 2.5 liters a day. The last sentence of the article noted that much of that water is already contained in the food we eat, but most people ignored that fact. Existing studies suggest we get enough fluids from our typical daily consumption of juice, milk and even caffeinated drinks, the Indiana University researchers found.