The relationship between salt and high blood pressure has been studied for over 100 years, finding that high salt intake can cause blood pressure to rise, while a low-salt diet can lower it. Epidemiological surveys have found that Eskimos living in the Arctic have a lower salt intake and lower blood pressure, mostly below 18.7/12.0 kPa (140/90 mmHg); blood pressure decreases in hypertensive patients after salt restriction. The reasons why high salt can elevate blood pressure may be related to the following factors:
1. High salt (high sodium) intake can cause water and sodium retention, leading to an increase in blood volume. At the same time, the increase in sodium ion levels inside and outside cells can cause cell edema, swelling of vascular smooth muscle cells, narrowing of the vascular lumen, increased peripheral vascular resistance, and consequently, elevated blood pressure.
2. High salt intake can enhance the sensitivity of blood vessels to vasoconstrictive factors like catecholamines, while also increasing the release of norepinephrine from sympathetic nerve endings. Additionally, it can increase the density of angiotensin receptors on the blood vessel wall, leading to excessive vasoconstriction, increased peripheral vascular resistance, and elevated blood pressure.
3. Sodium retention caused by high salt intake can increase intracellular sodium, inhibit the activity of the sodium-potassium-ATPase pump, and increase the influx of extracellular calcium into cells. Simultaneously, the increase in intracellular sodium eliminates the sodium ion gradient across the cell membrane, inhibiting the sodium-calcium exchange and reducing the excretion of cellular calcium. This leads to an elevated concentration of calcium ions in vascular smooth muscle cells, causing vasoconstriction, increased peripheral vascular resistance, and a rise in blood pressure.
Recently, a study by Xi'an Medical University found that some salt-sensitive individuals have mutations in the sodium pump gene. This gene mutation is dominant, meaning that people with this mutation will experience an increase in blood pressure after consuming more salt, and the more salt they consume, the higher their blood pressure will rise. This is the first such discovery in the study of human hypertension, which can explain why some people do not experience an increase in blood pressure despite high salt intake. Therefore, in the prevention and treatment of hypertension, it may be possible to screen for salt-sensitive individuals based on this finding to carry out targeted prevention. However, before determining whether you are salt-sensitive, it is still necessary to limit sodium salt intake, which should be controlled to 4-6 grams per day.