Folklore says, "The seven necessities of opening a door are firewood, rice, oil, salt, sauce, vinegar, and tea." Whoever lives in this world cannot do without firewood, rice, oil, and salt. The daily toil of the common folk is probably mainly for these necessities. Firewood has certainly changed; now people burn coal, gas, or natural gas. Rice may also not be a necessity, as Westerners eat bread, and the Europeanization of diet seems to have become a fashion in Eastern countries. As for oil, because cardiovascular and cerebrovascular diseases are on the rise, and high-fat diets are the main culprit, people have started to fear it. Only salt has been consistently preserved for thousands of years in our nation, which places great importance on dietary culture. Moreover, because it is vital to the people's livelihood—"food is the first necessity of the people"—salt is included in this "food."
Salt is indeed indispensable for the human body. Otherwise, why would sick people need to go to the hospital for an "IV drip"? When a person cannot eat normally, a lack of sugar intake can lead to "hypoglycemia": palpitations, trembling, cold sweats, and even starvation. A lack of salt intake can lead to "hyponatremic syndrome," characterized by general weakness and abdominal discomfort. There is also "hypochloremic alkalosis," which manifests as vomiting, shortness of breath, and even coma. Therefore, just like sugar intake, a certain amount of salt intake is necessary.
Excessive salt consumption is harmful to health!
The tyrannical landlord Huang Shiren snatched Xi'er, and Yang Bailai, filled with grief and indignation, drank a bowl of salt brine—the brine used for pickling vegetables—and died. A high concentration of salt solution can cause damage to the gastrointestinal mucosa, leading to acute erosive hemorrhage. It can also cause dehydration of body tissues, and a sharp increase in blood circulation can lead to acute heart failure. How could it not be fatal?
To illustrate the effect of salt on health, let's conduct an experiment: place a section of sausage casing into a cup of fresh water after filling it with brine and tying both ends. Before long, the fresh water in the cup will also become salty. Eventually, the salt concentration of the water inside and outside the casing will be the same. Conversely, if you place fresh water inside the casing and then put it into a cup of salt water, the water inside the casing will also become salty. It turns out that this sausage casing is a "semi-permeable membrane." The meat inside, of course, cannot get out, but the salt inside can seep out. This is the principle of "osmotic pressure" in physics. When the concentration of a certain substance in the solutions on both sides of the membrane is different, the membrane's permeability opens until the concentration of that substance in both solutions is balanced.
How much is just right?
That eating too salty affects health is no longer in doubt. Salt is also one of the essential foods for the human body. So how much should we eat to meet health requirements? Nutritionists recommend an intake of 5 grams per person per day. For a family of three, that would be 15 grams a day, or 450 grams a month for 30 days. However, one must not forget that soy sauce contains salt, pickled vegetables contain salt, and if you had a salted duck egg for breakfast, that salt also counts. Therefore, for the general public, it is really difficult to control an intake of 5 grams of salt a day. Even nutritionists probably cannot turn their kitchens into chemical laboratories to measure exactly how much salt they can eat in a day. However, the Chinese Nutrition Society has conducted a survey that has reference value. According to the survey, the daily salt intake for residents in northern China is about 15-18 grams, while for residents in southern China, it is about 10-12 grams. This makes things easier. It seems that our friends in the north need to reduce their salt intake by two-thirds, and our compatriots in the south by half. Although not very precise, it gives us a general idea.
Three types of people should avoid salt
1. Patients with kidney disease, liver cirrhosis with ascites, and heart failure
Urination increases the burden on the kidneys. People with kidney disease or poor kidney function urinate less, so excess salt cannot be excreted and accumulates in the body's tissues. To achieve balance on both sides of the membrane, the body absorbs water to dilute this salt. As a result, water accumulates in the body's tissues, which is the root cause of edema in kidney patients. Therefore, kidney patients cannot eat salt, which many people know. In fact, patients with liver cirrhosis and ascites also cannot eat too much salt; otherwise, the ascites will be difficult to resolve. Heart failure patients also cannot eat too much salt; otherwise, edema will be difficult to resolve. These are not difficult to understand.
2. Patients with high blood pressure cannot eat too salty
Patients with high blood pressure also cannot eat too salty. The causes of high blood pressure are many, some of which are not yet fully understood, but it is certain that it is related to the tension of blood vessels, the amount of blood pumped by the heart, and the total volume of blood circulation. High vascular tension, large heart output, and large blood volume can all increase blood pressure. Therefore, before the use of antihypertensive drugs, Western doctors used bloodletting to treat hypertensive crises. If patients with high blood pressure eat too salty, a large amount of salt intake passes through the intestinal mucosa and first enters the blood circulation. The salt content in the blood is high, and the body must absorb water to dilute it, so people feel thirsty and drink a lot of water. This water enters the blood, causing the blood volume to expand. Then blood pressure will rise. It's not that patients with high blood pressure cannot drink water. Because if there is no excess salt in the blood, water cannot be retained in it and is quickly excreted by the kidneys as urine. However, when the salt content in the blood is too high, it is different. Salt retains water in the blood, which increases blood pressure. Therefore, the reason why patients with high blood pressure cannot eat too salty is based on this principle.
3. Stomach cancer is prevalent in regions with high salt consumption
The harm of excessive salt intake is not limited to high blood pressure. The incidence of stomach disease among our people is extremely high. It is estimated that at least 20% of our people have suffered from gastritis or a duodenal ulcer in their lifetime. Among people with discomfort in the upper abdomen, eight or nine out of ten have gastritis upon gastroscopy. The causes of gastritis and gastric ulcers are also numerous. Excessive gastric acid secretion and Helicobacter pylori infection are important causes. Pathologists divide the causes of gastritis and gastric ulcers into two aspects: excessive attack factors and weakened defense factors. Excessive gastric acid and Helicobacter pylori infection are attack factors, while the weakening of the stomach's mucosal defense factors is another aspect. When people enjoy their food with all its flavors—sour, sweet, bitter, and spicy—what does the stomach use to protect itself? The stomach's mucosa secretes a layer of mucus that coats the mucosa, forming an excellent protective film.