SALT is essential for survival and in some salt-starved areas of the globe it was once considered precious. In the Roman Empire, for example, salt was not only considered as precious as gold but was used instead of gold. The soldiers who sweated salt as they conquered the world were paid in salt, hence the word “salary”, derived from the Latin salarium meaning official allowance.

But too much can be dangerous. The human body has an intricate homoeostatic system for controlling salt content. When the amount taken in or lost becomes too great, the system breaks down. Too little, and the anti-diuretic hormone slows the excretion of salt through the kidneys. Too much, and the ensuing thirst will encourage the person to drink so that sodium levels are diluted.

Cardiologists are not too concerned by an occasional salty meal, but a daily diet containing twice as much salt as necessary increases blood pressure and therefore the chances of heart attacks and strokes. If the average UK intake were reduced by a third, strokes would be cut by 22 per cent and heart attacks by 16 per cent. Adults should aim for a daily allowance of 6mg — the average now is 9-13mg.

Childrens’ kidneys are not as adept as adults’ at maintaining regular salt levels in the blood and tissues. An overdose in babies or small children can be lethal. So children have a lower salt requirement — a nine-year-old needs only half the amount of his parents.

A child died recently after being given the equivalent of 18 teaspoons of salt — this unbalanced his electrolyte system so much that it killed him.

The inability of childrens’ kidneys to cope with adult doses of salt was one reason why the weaning of babies at just a few weeks old — standard practice when my children were young — was postponed until four to six months.

It is now rather shaming to look at photographs of my middle-aged family when they were small babies and notice the puffy eyes that were probably a sign of premature weaning on to diets too rich in salt.

Too much salt produces generalised oedema — swelling as the result of water retention — and this results in an enlarged and failing heart, pulmonary congestion and cerebral oedema.

The brain of a shipwrecked mariner who drinks salt water, for instance, will be swollen and compressed within the skull and his behaviour will become increasingly bizarre as his essential organs also peter out.