Medical myths and cures

Medical Matters:I like sharing "home-made" nuggets of advice with my patients. At this stage, many anticipate my standard spiel about the usefulness of inhaling the vapours of Friar's Balsam or Olbus Oil in helping to clear blocked sinuses and to suppress a chesty cough.

Anyone presenting with back pain will almost certainly be told to ask their partner to rub olive oil over the inflamed musculature. Whether they decide to mix the olive oil with a certain illicit brew before applying is, of course, entirely up to the patients themselves.

My advice on this treatment must remain within the hallowed confidentiality of the doctor-patient relationship.

The common denominator in these and other pieces of home-spun advice is that I have used them myself. I "know" they work and so recommend them with a confidence that goes beyond the standard line of: "Let's try these tablets. If you still have symptoms in 10 days or so, will you come back to see me?"

But at what level do I know these remedies work? Personal experience combined with over 20 years of seeing their benefit in patients is good enough for me.

However, it may not be good enough for those who will be testing my competence in the future. And my "knowing" will certainly not cut mustard with the gurus of evidence-based medicine, for whom anything less than a series of well-designed, double-blind, randomised control trials is the minimum required before advocating the benefit of any form of treatment.

A review of medical myths in the end-of-year edition of the British Medical Journalreminded doctors of the need to re-examine their existing medical beliefs. It examined a number of beliefs, championed by physicians and the general public, and looked at them with a critical eye.

"Drink at least eight glasses of water a day" is advice we read about on a regular basis. You will undoubtedly have seen this nugget in the plethora of New Year columns advising healthy resolutions. It turns out that its origin may go back to a 1945 recommendation advocating the intake of 2.5 litres of water a day.

Crucially, however, the sentence "Most of this quantity is contained in prepared foods" seems to have been ignored. There are now a number of studies showing that we take enough fluids in a typical daily consumption of juice, milk and caffeinated drinks.

How many of you have advised your children not to read in a dim light? I know I have, based on the widely accepted "truism" that reading in poor light was bad for their eyesight.

Well, it's time to think again. There is apparently a multitude of research to prove that poor light does not hurt our eyes. According to the article, "the fearful idea that reading in dim light could ruin your eyesight probably has its origins in the physiological experience of eye strain. Sub-optimal lighting can create a sensation of having difficulty in focusing."

But increased rates of myopia (short sightedness) over the past few centuries cannot be blamed on poor light. People used to read by candle light, so if poor reading conditions were the cause of short sightedness, then myopia rates ought to have decreased as the quality of artificial lighting improved.

Morbid information about the body captivates the imagination and reinforces medical mythology. So why would we challenge the notion that hair and fingernails continue to grow after death?

But, according to forensic anthropologist William Maples, "it is a powerful, disturbing image, but it is pure moonshine. No such thing occurs."

What does happen is that dehydration of the body and skin desiccation cause the skin around hair and nails to retract. The skin's retraction creates an appearance of increased length because of the contrast between the shrunken tissues and the nail or hair. The actual growth of hair and nails requires continuous blood flow and a complex hormonal regulation that cease with death.

Old wives' tales still form the basis of people's health practices. Many old cures have been found to have a sound scientific basis. The one about fish being good for the brain has stood the test of time. Omega three fatty acids in oily fish protect the brain from strokes.

They may also help depression and there is some research suggesting a suitably fishy diet reduces the risk of dementia. And, of course, laughter really is the best medicine.

The authors of the medical myth article end on a rather serious note: "Physicians would do well to understand the evidence supporting their medical decision-making. They should at least recognise when their practice is based on tradition, anecdote or art.

"While belief in the described myths is unlikely to cause harm, recommending medical treatment for which there is little evidence certainly can. Speaking from a position of authority, as physicians do, requires constant evaluation of the validity of our knowledge."

Oh dear. It looks like sharing my favourite remedies with my patients is bad for them. Maybe the Medical Council will accept my plea bargain that I was simply sharing my beliefs. Just like I do when it comes to the benefits of a poitín and olive oil rub in the treatment of back pain.

• Dr Houston is pleased to hear from readers at mhouston@irish-times.ie  but regrets he is unable to reply to individual medical queries.