By Yechezkal Freundlich, Senior Science and Technology Editor
We ingest so many different types of products everyday that we don’t even put a second thought into what exactly we are consuming. Minerals, vitamins, chemicals and compounds – while all are important and crucial for the homeostasis of our body, there is a nutritional spectrum for each individual element in order to maintain the carefully controlled equilibrium that is the human ecosystem.
Before the explosive industrial complex and mass import/exports of goods globally – the globalization of the 19th century – some people would suffer and die from not consuming a small ingredient that was crucial for their survival, simply due to their financial or geographic situation. Fortunately, most had access to salt either by conventional mining or through food consumption (geographical locations that didn’t mine salt but rather ate foods with high salt concentrations like fish or meat), preventing the development of hyponatremia.
Sodium chloride (NaCl) is molecularly formed from the union of the sodium cation (Na) and the chlorine anion (Cl), creating an ionic compound. The two most common environments where NaCl can be found are in salt lakes and oceans, and in mines. This evaporite mineral halite, more commonly known as rock salt, remains as isometric crystals in deposits until quarried. Roughly 70% of earth’s surface is covered with water and 97% of the water on the earth is salt water; there is 78 million metric tons of salt per cubic kilometer of water, an inexhaustible supply.
Sodium, the cation in salt (NaCl), is responsible for maintaining bodily fluid and ensuring proper function for both muscles (contraction and relaxation) and nerves (nerve impulse). Table salt, which is purely NaCl, contains 40% sodium. While the ratio between sodium and chlorine is 1:1 in the ionic bond, that does not calculate for their atomic weights. Sodium is ~23 amu (atomic mass units) and chlorine is ~35.5 amu. Thus, sodium contributes less to the overall mass of the compound. This is important to note when calculating the total consumption of sodium per day, not NaCl per day. The human body needs around 200-500 mg/day of sodium to function normally and the FDA recommends ingesting <2,300mg/day, however, the average American consumes roughly 3,400mg/day, significantly exceeding the physiological requirement for the human body.
Research has shown that a high-sodium diet greatly disturbs the functions of the heart at a molecular level. Upon analyzing a high-sodium diet, scientists noticed an increased expression of β-myosin heavy chain, a protein linked to changes in myocardial mechanical performance. This alteration, in tandem with decreased expression of the α/β-myosin heavy chain ratio, leads to impaired heart function. Furthermore, high sodium intake stimulates myocyte enhancer factor 2 (MEF2) and nuclear factor of activated T cells (NFAT) transcriptional activity – key regulators of gene expression in cardiac muscle. These shifts are detrimental to the human body, as they disrupt the proteins responsible for calcium homeostasis, an important factor for maintaining proper myocardial contractility and heart rhythm.
Sodium’s role in regulating fluid balance means that excessive intake can cause fluid retention, increasing blood volume and, consequently, blood pressure. Hypertension, a primary risk factor for heart failure, places immense strain on the left ventricle of the heart, leading to left ventricular hypertrophy (LVH): a condition where the heart’s muscular walls thicken to compensate for the increased workload. If left unchecked, LVH can progress to heart failure and other cardiovascular complications that can be fatal. Studies have shown that a regression in sodium intake can reverse LVH in some cases and alleviate symptoms, improving arterial stiffness and endothelial function while reducing blood pressure.
Sodium’s detrimental effects are not confined to the heart and blood vessels. Excessive consumption is also strongly associated with other comorbidities, including chronic kidney disease (CKD) and stroke. The kidneys, responsible for filtering and excreting excess sodium, bear the brunt of high sodium diets. Over time, the increased workload can lead to impaired kidney function, which further exacerbates hypertension by disrupting the body’s ability to regulate blood pressure effectively.
Research suggests that sodium is associated with other diseases including stomach cancer, obesity, metabolic syndrome, autoimmunity, kidney stones, and osteoporosis. The theorized association with kidney stones and osteoporosis is via a common mechanism. Urinary sodium and calcium excretion are strongly correlated, thus, an excess salt intake can affect both sodium excretion (which will then stay in the blood) and calcium (which can cause kidney stones and osteoporosis). The majority of renal calcium reabsorption occurs passively in the proximal tubules, where it is coupled with sodium and water reabsorption through the effects of water reabsorption on the translumenal calcium gradient and by solvent drag (a passive movement of molecules through tight junctions in cells). These findings suggest that sodium loading and volume expansion will reduce proximal tubular fluxes and decrease net calcium reabsorption whereas sodium restriction and volume depletion will have the opposite effect. This a priori reasoning has been used to support the role for sodium restriction in preventing kidney stones.
Research also suggests that sodium restriction may play a role in directly improving cardiac muscle function. A lower sodium diet has been linked to an increase in the α/β-myosin heavy chain ratio, a marker of improved myocardial mechanical performance. This shift demonstrates the potential of dietary interventions to not only prevent but also reverse some of the damage caused by chronic sodium overload. By improving calcium regulation within cardiac cells, reduced sodium intake can restore more efficient heart muscle contraction and relaxation, ultimately improving cardiovascular health.
While sodium is essential for physiological processes such as muscle contraction, nerve signaling, and fluid balance, the fine line between necessary and excessive intake is often crossed, leading to widespread health implications. Obviously, elimination of salt consumption is not the solution since you might develop hyponatremia. This concern isn’t really pertinent since most processed foods: fish, cheese, meat, canned food, and even some vegetables contain salt. Simply, be mindful of what you are eating throughout the day and make sure not to have too much sodium consistently.