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It has been noted that the salts are more important for our life than food. Salt starvation will bring about an earlier death than food starvation. In animals natural salt deficiency never takes place, enough being present in food.
In man also total salt deficiency is never seen under natural conditions but partial deficiency or deficiency of individual elements or salts may take place in cases of increased excretion, such as profuse sweating, diarrhoea, haemorrhage, etc., or by taking a faulty diet or in certain diseases of the endocrine glands, for instance, parathyroid, adrenal cortex, etc.
The following is a brief summary:
1. In Animals:
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With complete deprivation of salts, the function of the entire body becomes upset. The animal becomes weak, loses appetite—food is retained in the stomach for a long time in an undigested form (showing absence of gastric secretion and motility) and is finally vomited out. The animal gradually fails to move about, shows signs of paralysis, loses consciousness and ultimately dies.
Salt loss in the urine becomes extremely low, almost all being reabsorbed by the tubules as a measure salt economy. If under such conditions food (without salts) is given, the salt excretion is much lower than when food is withheld. This indicates that inorganic salts remain in some sort of chemical combination in the cell.
During food starvation the animal has to live by burning its own body tissues; the salts, thus freed, diffuse out of the cells and appear in the urine. Thus food starvation increases the salt loss and enhances the deficiency effects. Since potassium remains mostly in the cells, food starvation which leads to the breakdown of the cells will increase the potassium content of the urine. In other words, potassium excretion is a good guide as to the degree of disintegration of cells going on in the body.
2. In Man:
i. With a Salt-Free Diet:
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With a salt-free diet, the NaCl almost disappears from urine due to maximum tubular reabsorption. Caffeine under this condition increases the salt loss by depressing the reabsorption of salts and water by tubules. So that caffeine will increase the salt deficiency and also causes dehydration.
ii. If Salt Deficiency be Induced:
If salt deficiency be induced, by producing excessive sweating (giving water drinks without salts, only to replace the loss of water) the plasma non-protein nitrogen (N.P.N.) rises, the urea may rise to 80 mgm per 100 ml, the man may be sick showing signs of early uraemia. This is probably, at least partly, due to the depression of kidney functions. The symptoms quickly clear up by giving saline drinks. In those conditions where the man or the animal has to undergo a lot of sweating, he should always be given saline drinks. Otherwise, ill-effects may be produced.
iii. Heat Cramps:
Deficiency of salts, particularly of NaCl, occurs in men doing heavy muscular work in hot and moist atmosphere. Such people are found to suffer from temporary painful contraction of skeletal muscles. This effect is due to salt loss as well as dehydration. The blood becomes thick, haemoglobin concentration rises, blood NaCl falls. 1% salt solution in water if taken by such subjects will lead to a speedy cure.
iv. A sense of Fatigue, Weakness and Even Temporary Loss of Consciousness:
A sense of fatigue, weakness and even temporary loss of consciousness, have been reported in man doing even sedentary work in hot humid climates. The cause has been suggested to be, at least partly, sweating and salt loss. Saline drinks will bring about a speedy cure. In addition to the above, deficiency of individual elements may lead to specific harmful effects [Table 10.3]
