Saline solution

The idea of using electronic methods within a microwave oven to precisely detect the levels of salt and fat in food (News, 1 October) may, at first, seem to be a good idea.

However, the issue of salt in food has almost become fashionable, to be added to the recommendation that we should all aim to eat at least five pieces of fruit and vegetables every day.

The image being presented almost gives the impression that salt is completely detrimental to health and should be avoided completely. Sadly, this is far from the truth, as salt is essential not only to life, but to good health.

It has always been that way as the body's salt/water ratio is critical to metabolism. Human blood contains 0.9 per cent salt (sodium chloride) — the same concentration as found in United States Pharmacopeia (USP) sodium chloride irrigant commonly used to clean wounds.

Salt maintains the electrolyte balance both inside and outside cells. This means that while having too much salt in the diet can be damaging to health, the same is true if too little is present.

A low salt diet is an absolute disaster in some illnesses.

In adrenal exhaustion, for example, the body fails to produce adequate levels of the steroid hormone aldosterone. This means that the body is behaving in a manner where it is detecting insufficient salt. So it tries to increase the effect of existing salt by removing as much water as possible to increase the concentration of what remains.

The symptoms that follow include lack of thirst, excessive volume and frequency of urination, low blood pressure, and postural hypotension — feeling faint when standing. in some cases that is exactly what happens, the sufferer faints as soon as he or she attempts to stand.

The solution to the problem is just that, a solution of salt water. To make this palatable, it is delivered as an isotonic electrolyte drink where the sugar and salt levels have the same concentration as should be present in the blood, and the mixture commonly flavoured to mask the less-than-pleasant taste.

However, for some sufferers of adrenal exhaustion, the daily salt requirement is 42g — about seven times the normally recommended intake.

in such cases this is simply to compensate for the net salt loss, where this excessive loss is through perspiration and urination.

Andrew Porter

Cambridge