Before the advent of modern industrialized society, man must have been much more happier than to day as the maxim goes "ignorance is bliss"! The science of health, nutrition and food has thrown up massive information and newer knowledge about the intimate connection amongst the three branches and it is debatable whether this has made man happier. The pundits do not feel tired blaring out what is good and bad for you though they never have unanimity, often contradicting each other. If one goes by the current perception, what is left behind after castigating all known foods in one way or the other, for the man to derive his 2000 calories, 50g each of proteins and fats and carbohydrates that is needed to sustain the life?. Too much protein is not good, fats are to be strictly moderated, high carbohydrates are to be avoided, sugar consumption is dangerous and salt is white poison, all being propagated by knowledgeable as well as not-so-much knowledgeable pundits. The only things left are grass and some fish which have not yet been implicated in any health disorders so far!
Salt, which is chemically Sodium Chloride (NaCl), is an essential nutrient and without it in the body, life can be extinguished within 48 hours. It helps to maintain right balance of fluids necessary for homeostasis, aids transmission of nerve impulses and influences contraction and relaxation of muscles. Kidneys have the vital function to regulate the sodium content (Na) in the blood by retaining it when there is a shortage and excreting it through urine under excess conditions. If kidneys cannot eliminate enough Na, it starts to accumulate in the blood. Since Na attracts water, blood volume increases putting a strain on the heart in pumping the blood and consequently increasing the pressure on the arteries. High blood pressure in turn can damage kidneys. Ideally, the optimum Na concentration in blood should be 135-145 mEq/l. High levels of Na can cause hypernatremia when blood pressure increases abnormally. Low levels less than 135 mEq/l leads to hyponatremia, causing muscle cramps, nausea, vomiting, dizziness and eventually shock, coma and death. Of course this happens only with acute gastroenteritis or severe sweating or water intoxication.
There is no universal agreement on optimum salt intake in a diet amongst experts. Average Indian consumes about 10g of salt daily, equivalent to about 4000 mg of Na while ICMR recommendation is only 4g. But some reports put the figure as high as 12kg per year. In contrast an American consumes 5000 mg Na though American Heart Association recommends a daily intake of only 2400 mg of Na. There are experts who feel that just 500 mg Na is sufficient for vital body functions though there are also contrary views that high salt consumption is good for longevity, especially if more than 800 mg Calcium is also taken through the diet. USA, Canada, Australia, UK and Portugal have 2400 mg Na as safe limit, while the Netherlands with 3600 mg of Na per day, Belgium with 3500 mg, Germany with 4000mg and Sweden with 800mg have different standards. In a typical diet in rich countries 10% of of total Na ingested comes from natural foods, 15% from added salt and 75% from processed/packed foods. Probably in India also this may be true since consumption of namkins (snacks and savories) is very high amongst Indian population.
Many doctors feel reducing daily salt consumption by 3 g could result in a 20% reduction in mortality due to strokes and controlling the salt intake by restricting its level in the diet at 5-6g or a teaspoon a day can be highly beneficial to every body in the long run. Salt substitutes are mostly based on Potassium Chloride, presumably due to the ability of the human body to manage this salt better but those affected by kidney diseases, too much Potassium can also be risky. Recent development of taste boosters that enable dramatic reduction of salt in foods without affecting the taste, may yet be the ultimate answer for controlling the salt dependent epidemic like blood pressure with least pain.
As of now it is advisable to control salt intake if the recent findings of American Society of Hypertension are taken seriously. The essence of the finding is that lower the salt intake lower will be the blood pressure without any adverse effect on other systems in the body. Being a well organized study, the above guideline can be followed till any contrary reports supported by scientific data appear on the horizon.