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Regards to all our listeners!

I'm Rob Logan, Ph.D., senior staff, U.S. National Library of Medicine substituting this week for Donald Lindberg, M.D, the Director of the National Library of Medicine.

Here is what's new this week in MedlinePlus.

To listen to Dr. Lindberg's comments, click here

Some widely held medical beliefs among physicians are myths; a study recently published in the British Medical Journal finds.

Researchers at the Indiana University School of Medicine found little evidence to support seven medical assumptions, which they assert (but do not demonstrate) are widely held among physicians.

To begin, there is no clinical evidence that an adult should drink eight glasses of water a day. The study's two authors find the belief may stem from a recommendation in the 1940s that adults should drink 2.5 liters of water a day. However, the idea had no supporting evidence --and even the original recommendation noted that water could be picked up from food intake. The reality is drinking excess water, or liquid from other non-alcoholic sources, is potentially harmful.

Second, humans use much more than 10 percent of their brain power -- all the time. The researchers note the belief we use only 10 percent of our brain seems to be more than a century old. While the idea is often attributed to master physicist Albert Einstein, the study finds no evidence he said or wrote it. Conversely, brain imaging studies find no area of the brain is inactive. Apparently, most areas in our brain are far more involved all the time than many of us assumed.

Third, hair and fingernails do not grow after death. While often discussed in movies and by comics, the growth of hair and nails requires a hormonal balance that does not occur after one dies.

Fourth, shaving does not cause hair to grow back faster, darker or coarser. The study's authors note that clinical trials which are 80 years old refute this claim, which somehow manages to persist. Actually, shaving removes a dead portion of hair -- not the live part that lies below the skin. So, growth is unlikely.

Shaved hair lacks a finer taper that occurs at the ends of unshaven hair, so it may appear to be coarse -- but it is not. And, new hair appears darker only because it is has not been touched by sun, air and the chemicals we splash on our face. Apparently, hair lightens up quickly -- (unlike a colleague who cannot take a joke).

Fifth, ophthalmologists believe that reading in dim light does not result in eye damage. It may cause eye strain, but the authors note that permanent damage is highly unlikely. There is one study that suggests myopia could occur if a heavy reader uses low light and holds books or magazines close to his or her face. However, this is akin to a current hypothesis rather than a medical fact.

Sixth, eating turkey does not make you drowsy. The myth occurs, the authors write, because one of turkey's ingredients, tryptophan, is used in sleep aids. But this is a case where the dose makes the difference. The amount of tryptophan in turkey is too low to result in drowsiness. Interestingly, chicken and minced beef contain similar levels of tryptophan.

The reason we may feel drowsy after Christmas or Thanksgiving turkey dinners, the authors write, is because any large, solid meal (such as turkey, stuffing, vegetables, bread, puddings and wine) induces sleepiness because blood flow and oxygenation to the brain decrease. Also, meals high in protein and carbohydrates (such as turkey and sweet potatoes) make us sleepy. So, it's the complete package rather than an entrée, or a garrulous guest that puts us to sleep.

Finally, there is no evidence that cell phones cause electromagnetic interference in hospitals. While there was early evidence that received publicity about 15 years ago, subsequent rigorous testing has not found any evidence of a link. In contrast, the authors note some recent research shows cell phone use among anesthesiologists was associated with less risk of medical errors or injury because the phone eased communication delays.

The authors conclude that physicians should re-examine beliefs and question the falsehoods sometimes advanced as medicine. Their advice that existing beliefs sometimes require a reality check is of course, fine advice for all of us as a new year begins.

While MedlinePlus does not have links to web sites that bust medical myths, there is an excellent section that helps you to evaluate the medical information you see every day (especially from internet sources of health information -- including the National Library of Medicine).

MedlinePlus' 'evaluating health information' health topic page contains an interactive tutorial that introduces you to how to evaluate the medical information you find online, or see in the mass media. It helps you decipher when information is or is not based in the latest evidence using well-established medical research techniques. The interactive tutorial lets you hear the words on the screen, so it is ideal for those who are vision impaired, are novice English speakers, or are not used to medical terms.

To find it, type 'health information' in the search box on MedlinePlus' home page, then, click on 'evaluating medical information' (National Library of Medicine).  The interactive tutorial is in the 'start here' section.

Among many other resources within MedlinePlus' 'evaluating health information' health topic page are:

• A guide to help you critically evaluate health information in the news media -- from the Harvard School of Public Health. The guide is in the 'overviews 'section
  
  
• A users guide to determine the quality of health information on web sites from the Medical Library Association, which also is accessible within the 'overviews' section
  
  
• A guide to help you critically assess 'miracle' medical claims that is provided by the Federal Trade Commission (which is accessible in the 'related issues' section).

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It was nice to be with you….

Dr. Lindberg returns in the future.

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