Turkey dont make ya sleepy!!

[Jack Bennest]

STUDY: DEBUNKING POPULAR WISDOM

Eight glasses of water a day - and other myths

PAUL TAYLOR

December 21, 2007

You've heard these tidbits of medical wisdom many times before - possibly from your own doctor:

Drink eight glasses of water a day.

Reading in dim light ruins your eyesight.

We use only 10 per cent of our brains.

But they aren't true or there is little scientific evidence to back them up, according to a report by two U.S. researchers in the British Medical Journal.

The year-end edition of the normally staid journal is usually devoted to lighthearted health issues.

The myth-busting report, being published today, certainly falls into this time-honoured tradition.

Even so, the researchers have a serious message for their medical colleagues: Be careful about the advice you dispense - it may be incorrect.

"We can be wrong and need to question what other falsehoods we unwittingly propagate as we practise medicine," they caution in the article.

For their debunking exercise, Rachel Vreeman of the Indiana University School of Medicine and Aaron Carroll at the Regenstrief Institute in Indianapolis looked at seven commonly held beliefs espoused by physicians and the general public.

They used Medline, a database of medical literature, as well as Google to search for evidence to support or refute each of the popular notions.

And despite their widespread acceptance, all the selected medical beliefs turned out to be either "unproved or untrue."

Here is what their online investigation revealed:

Drink at least eight glasses of water a day. There's a lack of medical evidence showing you need to down this much water daily.

This common prescription can be traced to a 1945 medical recommendation that stated: "A suitable allowance of water for adults is 2.5 litres daily in most instances. An ordinary standard for diverse persons is one ml for each calorie of food. Most of this quantity is contained in prepared foods."

If the last, crucial sentence is ignored, the statement could be interpreted as an instruction to drink eight glasses of water a day. Evidence suggests you can meet all your fluid needs through food and other beverages including juices, milk and even caffeinated drinks.

We use only 10 per cent of our brains. This belief, which dates back at least 100 years, doesn't stand up to studies of patients with brain injuries, which suggest that damage to almost any area of the vital organ has specific and potentially lasting effects.

Imaging studies also reveal that no region of the brain is completely silent or inactive.

Hair and fingernails continue to grow after death. Morbid curiosity and popular culture seem to keep this myth alive.

As former Tonight Show host Johnny Carson once joked, "For three days after death hair and fingernails continue to grow but phone calls taper off."

Still, this belief may have originated from an optical illusion caused by a shrinking or retraction of skin around the fingernails and scalp after death. The growth of hair and nails, however, "requires a complex hormonal interplay" only possible in a living person.

Reading in dim light ruins your eyesight. Dim lights may contribute to difficulty focusing, leading to dry eyes and eye strain. But once lighting conditions improve, these side effects don't persist for long.

Shaving causes hair to grow back faster or coarser. Strong evidence disproves this common belief. Shaving removes the dead part of hair, not the living section below the skin's surface, so it can't affect the rate or type of growth. What's more, the stubble resulting from shaving grows out without the finer taper seen at the ends of unshaven hair, giving the impression of coarseness.

Eating turkey makes people especially drowsy. This bit of ill-founded folk wisdom stems from popular reports that turkey meat is a rich source of tryptophan, an amino acid that plays a role in sleep and mood control. In reality, turkey has the same amount or less tryptophan than other sources of protein.

Possibly the gobbling fowl gets a bad rap because it is usually served at feasts such as Thanksgiving and Christmas. Any large meal can induce sleepiness because blood flow to the brain temporarily decreases while food is digested.

Mobile phones are dangerous in hospitals. This modern-day myth has been fuelled by news reports that cellphones disrupt medical equipment. Many hospitals have banned the devices, further perpetuating the belief.

But rigorous testing in Europe found minimal interference and only at distances of less than a metre. And recent technological improvements may be lessening even this minimal interference. In fact, a recent study concluded that cellphones add to hospital safety because doctors can be immediately contacted when there is a medical emergency.