A belly full of turkey is no excuse for laziness over the holidays, according to American researchers who have published a list of common medical myths just in time for the holidays.

In an article published in the year-end edition of the British Medical Journal this weekend, the Indianapolis-based team of Rachel Vreeman and Aaron Carroll identified seven widely held health beliefs in need of critical review. They included the notion that people should drink at least eight glasses of water a day, that we only use 10 per cent of our brains, and that turkey causes fatigue.

"These medical myths are a light-hearted reminder that we can be wrong and need to question what other falsehoods we unwittingly propagate as we practice medicine," the authors say in the article.

The researchers used Google and Medline, an archive of medical literature, to find evidence to support or debunk health claims endorsed by physicians and the general public.

They found that while some myths had scanty medical evidence to support their claim, others had been proven wrong outright.

The myth list includes:

• People should drink at least eight glasses of water a day: Most of the water we need is available to us through the food and other drinks we ingest, including milk, juice and even caffeinated drinks such as coffee and tea. The standard water to food ratio is 1 millilitre for each calorie.

• We only use 10 per cent of our brains: Rising to fame at the turn of the last century, the statement has been erroneously attributed to Albert Einstein. Various studies have since concluded that no part of the brain is ever completely dormant.

• Hair and fingernails continue to grow after death: This macabre myth relies on the appearance of longer nails or hair as dehydrated skin begins to shrink and shrivel. Actual growth, which requires a complex hormonal process, does not occur.

• Shaving hair causes it to grow back faster, darker or coarser: The stubby regrowth may seem coarser because it lacks the fine taper of unshaven hair and has not been lightened by the sun or chemicals. But because shaving removes only the dead portion of hair lying above the skin's surface, it does not affect the rate or type of growth.

• Reading in dim light ruins your eyesight: It's probably more difficult for most people to read in low light, which decreases the rate of blinking and dries out your eyeballs. However, the strain isn't permanent. 

• Eating turkey makes people especially drowsy: This popular holiday poultry contains an amino acid, tryptophan, associated with sleep and mood control, but so does chicken and ground beef. Food fatigue is more likely caused by eating heavy meals that restrict blood flow and oxygenation to the brain, or by wine used to wash it all down.

• Mobile phones create considerable electromagnetic interference in hospitals: After a lot of media hype but considerably less actual evidence, a 2007 study found mobile phones "used in a normal way" do not interfere with medical devices. In fact, a large survey of anaesthesiologists suggests mobile phones actually improved safety by enabling quicker communication in an emergency.