Hypertension: Salt restriction, sodium homeostasis, and other ions

Abstract

Salt is composed of Sodium Chloride (NaCl) which in body water becomes essential electrolytes, viz., Sodium (Na⁺) and Chloride (Cl⁻) ions, including in the blood and other extracellular fluids (ECF). Na⁺ ions are necessary cations in muscle contractions and their depletion will effect all the muscles in body including smooth muscle contraction of blood vessels, a fact which is utilized in lowering the blood pressure. Na⁺ ions also hold water with them in the ECF. Na⁺ homeostasis in body is maintained by thirst (water intake), kidneys (urinary excretion) and skin (sweating). In Na⁺ withdrawal, body tries to maintain homeostasis as far as possible. However, in certain conditions (e.g., during exercise, intake of drugs and in disorders causing Syndrome of Inappropriate Anti Diuretic Hormone Secretion (SIADH), diuretics, diarrhea) coupled with moderate or severe dietary salt restriction (anorexia nervosa), hyponatremia can get precipitated. Hyponatremia is one end point in the spectrum of disorders caused by severe Na⁺ depletion whereas in moderate depletion it can cause hypohydration (or less total body water) and lower urinary volume (U v ). Moreover, salt sensitivity varies in various populations leading to different responses in relation to dietary Na⁺ intake. Diabetes and Hypertension often co-exist but Na⁺ withdrawal in salt sensitive subjects worsens diabetes though hypertension gets better and reverse occurs in salt loading. Therefore, Na⁺ or salt restriction may be non-physiological. In hypertensive subjects other alternatives to Na⁺ withdrawal could be Potassium (K⁺) and Calcium (Ca⁺²) supplementation. Further studies are required to monitor safety/side effects of salt restriction.

Estimation of mean population salt intakes using spot urine samples and associations with body mass index, hypertension, raised blood sugar and hypercholesterolemia: Findings from STEPS Survey 2019, Nepal

“…Sodium is the principal cation in extracellular fluid in the body and is an essential nutrient necessary for normal cell function and neurotransmission [ 1 ]. However, despite being a major source of sodium, high dietary salt intake is associated with high blood pressure, which is recognized as a risk factor for non-communicable diseases (NCDs), in particular cardiovascular diseases (CVDs), including heart attack and stroke [ 2 , 3 ].…”

The Hyponatremia Epidemic: A Frontier Too Far?

“…A normal concentration of sodium ions (Na + ) in plasma and extracellular fluid is essential for nerve and muscle electrical conduction ( 1 , 2 ). If dietary salt intake does not equal or exceed salt loss in urine and sweat, a fall in Na + below concentrations that allow normal function will occur ( 2 ). This condition (hyponatremia) causes dysfunction of brain and body; much Alzheimer’s disease has been attributed to hyponatremia ( 3 ).…”

“…The fall in BP with salt restriction may be greater in patients with diabetic kidney disease than in normals ( 33 ). In a very large study in European White ethnic subjects, in whom sodium intake was accurately assessed by measuring 24-h urinary sodium output, no correlation between salt intake and blood pressure was shown ( 34 ), suggesting that the earlier studies on mixed ethnic populations were unsound, as salt sensitivity varies in various populations ( 2 ). When normal people with normal renal function ingest sodium, any excess is excreted in the urine, and total body sodium remains normal ( 35 ).…”

“…In these patients, who are the majority, suppression of the activity of the renin–angiotensin system by angiotensin-converting enzyme (ACE), or angiotensin II receptor antagonism, is effective in both controlling the BP and reducing the complications of hypertension. Diabetes also occurs in the insulin resistance triad of obesity/hypertension/diabetes, but salt restriction makes diabetes worse ( 2 ). It is illogical for such patients to also indulge in salt restriction, unless they have kidney disease, so doctors do not recommend it.…”

Efeito da sobrecarga salina no remodelamento vascular.

“…Como era de se esperar, verificamos aumento sódio excretado na urina tanto em machos como em fêmeas. Como estes animais, ao receberem sobrecarga salina, precisam eliminar o excesso de líquido e de sal, a resposta normal é de aumento tanto de volume de urina como de sódio excretado (GUPTA, et al,2011). Era de se esperar que houvesse aumento de cloreto excretado, mas este foi verificado apenas em fêmeas.…”