How does salt intake affect blood pressure? A scientific guide to limiting salt intake and supplementing potassium.

Salt: The relationship between salt and hypertension has been studied worldwide for over 100 years, finding that high salt intake can cause elevated blood pressure, while a low-salt diet can lower it. Epidemiological surveys have shown that Eskimos living in the Arctic have low salt intake and low blood pressure, mostly below 140/90 mmHg; blood pressure also decreased in hypertensive patients after limiting salt intake. The ability of high salt intake to raise blood pressure may be related to the following factors:

(1) The main component of table salt is sodium chloride. Sodium and chloride ions are present in the extracellular fluid, while potassium ions are present in the intracellular fluid, maintaining a balance under normal circumstances. When sodium and chloride ions increase, changes in osmotic pressure lead to an increase in extracellular fluid, causing sodium and water retention, increased intercellular fluid and blood volume, and simultaneously increased venous return, ventricular filling, and cardiac output, which can raise blood pressure.

(2) Increased sodium ion concentration in the extracellular fluid leads to a greater sodium ion concentration gradient between the intracellular and extracellular spaces, resulting in increased intracellular sodium ion concentration. This causes cell swelling. Swelling of the smooth muscle cells in the arteriolar walls narrows the lumen, increasing peripheral resistance. Furthermore, it increases the responsiveness of the arteriolar walls to vasoconstrictors in the blood (such as adrenaline, noradrenaline, and angiotensin), causing arteriolar spasm and increasing resistance in small arteries throughout the body, thus raising blood pressure.

Currently, numerous studies worldwide on the relationship between salt and hypertension indicate a positive correlation between salt intake or urinary sodium excretion (indirectly reflecting sodium intake) and hypertension; that is, the more salt a person consumes, the higher their blood pressure. Research in my country also shows that northerners consume more salt than southerners, and the incidence of hypertension also shows a trend of higher in the north and lower in the south.

Does consuming more salt necessarily lead to hypertension? The answer is no. Research indicates that approximately 20% of the population develops hypertension due to excessive salt intake; these individuals are medically termed salt-sensitive. The majority (around 80%) of healthy individuals do not develop hypertension even with slightly saltier meals. However, it is currently impossible to distinguish between salt-sensitive and non-sensitive individuals in the general population. Therefore, from a hypertension prevention perspective, it is important to appropriately control salt intake and change the habit of consuming heavily salted foods.

For patients already diagnosed with hypertension, limiting salt intake is also beneficial. Practice has shown that in the early stages of hypertension or in patients with mild hypertension, simply limiting salt intake can normalize blood pressure. For patients with moderate to severe hypertension, limiting salt intake can not only improve the efficacy of antihypertensive drugs but also reduce the dosage, thus significantly reducing adverse reactions and medication costs. Therefore, whether from the perspective of hypertension prevention or treatment, limiting salt intake is beneficial.

Salt restriction is particularly suitable for high-risk groups such as those with a family history of hypertension, overweight individuals, those sensitive to salt-induced blood pressure increases, the elderly, those with heart or kidney dysfunction, and those with hypertension characterized by increased blood volume. How can we limit salt intake in daily life? Generally speaking, we ingest salt from three sources: the sodium content of food itself, the sodium added during cooking or eating, and the salt added during food processing for preservation, flavoring, and coloring. Limiting salt intake mainly involves controlling the amount of salt used during cooking and at the table. A family of three should not consume more than 250 grams of salt per month, which is about one teaspoon (approximately 3 grams) per day. Some people feel that if they use too little salt, the food will be bland and unappetizing. In fact, the daily physiological salt requirement is 2 grams. Excessive salt intake is an acquired, unhealthy taste. In addition, we should try to eat less high-sodium foods such as pickled products, animal organs, and shellfish. Grains and fruits contain relatively little sodium. Even alkali-soaked steamed buns contain sodium; eating 250 grams of alkali-soaked steamed buns is equivalent to adding 2 grams of salt. Potassium can counteract the harmful effects of salt on blood pressure and blood vessels, and also has an independent role in preventing stroke. Potassium supplementation not only lowers blood pressure but can also reduce the dosage of antihypertensive medications, and may be more effective for people with low potassium intake (such as residents of northern my country). To supplement potassium, eat more potassium-rich foods such as kelp, seaweed, black fungus, yam, bananas, potatoes, fish, tomatoes, and dried mushrooms. Limiting salt intake and supplementing potassium is more effective in preventing and treating hypertension and stroke than simply limiting salt intake. Consuming low-sodium, high-potassium "low-sodium salt" or "health salt" can achieve the dual effect of limiting salt intake and supplementing potassium.

To prevent hypertension, it is still necessary to limit sodium intake to 4-6 grams per day until it is determined whether one is salt-sensitive.