IS SALT ALWAYS BAD FOR YOU?

Most evolutionary theories support that life started in the sea with salt water billions of years ago. Salt is one of the oldest cooking ingredients known to man. Sumo wrestling warriors throw salt before the fight, as salt is believed to have the purifying power. But it has been born out that salt is like a poison and it should be reduced or avoided in the diet. Time after time, the media and nutritionists hammer salt can cause hypertension, heart failure, stroke, cancers and kidney damage. But these anti salt advocates do not understand how sodium works in the human body, and how essential it is to the human body. Yes , salt may cause the above conditions if there is a kidney disease, or other metabolic diseases but nothing happens if a healthy person takes salt according to his or her own taste. 

This can be very well explained by understanding human physiology on sodium metabolism.  Sodium or Na+ is required for sending messages by creating ‘action potentials’. Sodium is concentrated outside the cell, called extracellular compartment, while potassium is intracellular. The inward flow of sodium ions increases the concentration of positively charged cations in the cells of neurone and causes depolarization. When  the potential of the cell is higher than the cell\'s resting potential, it triggers ‘action potential’ and sends message down the axons of the neurone.  Once the potential inside the neurone  is higher, it fires causing a wave of impulse which propagates further. This happens not only in neurones, but also in muscle cells. 

Sodium is also required for fluid and electrolyte balance through osmosis, and keeping blood pressure. Hyponatraemia or reduced sodium in the blood causes headache, confusion. loss of energy, drowsiness, fatigue, restlessness, irritability. muscle weakness, spasms, cramps, seizures and coma. In my clinical experience, I have helped a lot of patients with weakness, dizziness and cramps by advising them to increase the amount of salt in their diet. Addison’s disease is a condition whereby the adrenal gland secretes less aldosterone and it manifests many of the above symptoms. Aldosterone is required for sodium re-absorption by kidneys.

Glomeruli (capillaries) of a healthy kidney filter 100% water and sodium, but tubules which collect water and sodium, reabsorb 99.4%of the water and sodium. Generally, water follows sodium due to the osmotic effect. More release of aldosterone from adrenal gland causes more re-absorption. Glucose is reabsorbed 100%,Potassium is reabsorbed 88%, Calcium is reabsorbed 99%, urea is reabsorbed only 50%, whereas creatinine is not reabsorbed at all. Higher the percentage of the substance reabsorbed indicates their functional utility in the body. For the mechanism of homoeostasis  sodium is very essential to the body.

In physical stress such as trauma and in mental stress there will be a release of adrenaline and noradrenalin and other hormones from adrenal gland which in turn will increase the blood pressure. This is a body defence mechanism in adverse condition to maintain blood pressure  in bleeding and losing blood volume. Adrenaline and noradrenaline help to constrict glomeruli, and  decrease filtration of sodium and water, thereby increasing volume and the blood pressure.   

Normal daily intake of salt (NaCl)  is  6 grams (2.4gm sodium) for adults that is around one teaspoon of sodium and for children between 1 and 3 years, it is much less at 2 grams (0.8gm sodium) of salt per day. Most of the processed food contain salt. Therefore, it should be accounted for in the daily intake. But if a healthy person takes more salt, say 7 grams per day, according to his or her own taste, then the person excretes 14.8% of 7 gram or 1.036 grams not reabsorbed. Once the kidneys excrete more sodium, to equilibrate the osmosis, water follows it causing dehydration. That is the reason, why delicious Chinese or Indian meal with hidden high salt content makes one thirsty. The kidneys are capable of increasing the excretion of sodium from 40mEq to 220 mEq/L per day. This can be demonstrated by measuring sodium content in 24 hour urine in different diet with less or more salt. If the kidneys are damaged, they may not be able to remove the sodium, and the resultant water log causes hypertension, oedema due to more extra cellular volume.  

The National Heart Lung and Blood Association report that 500 mg is a safe daily minimum intake of sodium. This is 20% of the maximum (6gram salt or 2.4gram sodium) one can safely take per day. This amount will be enough to maintain the bodily functions that require sodium. If someone regularly takes processed food, then the person gets 90% sodium from the salt added during cooking and the salt naturally occurring  in meat, fish and other raw food items. To increase the taste, an healthy person can still add 10% more salt. But if someone does not add salt while  cooking and not put salt salt in the food on the table, the person can get deficiency of sodium. These are manifested by headache, nausea, irritability, weakness, and cramps.  

The purpose of this article is to highlight the significance of salt  and that it is not a culprit as most people think. I had occasions when I could not enjoy any food when I went to have meals with my relatives in India and America. They prepare food without any salt and do not provide salt on the table to make the dinner as unpalatable as they can. My explanation on the above lines did not change their deep rooted dislike for salt. Salt has been referred to many times in the Holy Bible, as it was precious for life and required for preserving food. Let me quote Jesus’ Sermon on the mount “ You are the salt of the earth”( Matthew 5.13).