Salt is indispensable in people's life. The total amount of sodium ions contained in adults is about 60 g, of which 80% exists in extracellular fluid, namely plasma and intercellular fluid. Chloride ion also mainly exists in extracellular fluid. The physiological functions of sodium ions and chloride ions mainly include the following points:
1. Maintain osmotic pressure of extracellular fluid.
Na and Cl are the main ions to maintain the osmotic pressure of extracellular fluid. K and HPO4 are the main ions to maintain the osmotic pressure of intracellular fluid body. In the total cation of extracellular fluid, Na accounts for more than 90%, and in the total anion, Cl accounts for about 70%. Therefore, salt plays an important role in maintaining osmotic pressure and affects the movement of water in human body.
2. Participate in the regulation of acid-base balance in the body.
Sodium bicarbonate formed by Na and HCO3 has buffering effect in blood. Cl and HCO _ 3 also have a balance between plasma and red blood cells. When HCO 3 permeates from red blood cells, the anions in red blood cells decrease, and Cl enters red blood cells to maintain the electric balance. or vice versa, Dallas to the auditorium
3. Chloride ion participates in the generation of gastric acid in vivo.
The gastric juice is strongly acidic, and the pH value is about 0.9 ~ 1.5. Its main components are pepsin, hydrochloric acid and mucus. The parietal cells of the gastric gland can secrete hydrochloric acid. Parietal cells transfuse bicarbonate into blood and secrete hydrogen into gastric juice. At this time, Cl enters the gastric juice from the blood through parietal cells, maintaining the electric balance. Why can't such strong hydrochloric acid erode the stomach wall in the stomach? Because there is a kind of mucus cell in the gland of the stomach, the secreted mucus forms a layer of mucus about 1 mm ~ 1.5 mm thick on the surface of the gastric mucosa, which is usually called the barrier of the gastric mucosa. Under the attack of acid, the gastric mucosa will not be digested by digestive enzymes and form ulcers. However, drinking alcohol will weaken the barrier function of gastric mucosa and often increase the possibility of causing gastric ulcer.
In addition, salt can also maintain the normal excitability of nerves and muscles. When a large amount of extracellular fluid is lost (such as massive bleeding and sweating) or food is short of salt, the content of sodium ions in the body decreases, and potassium ions enter the blood from cells, which will lead to blood thickening, less urine and yellow skin. The human body's demand for salt is generally 3 to 5 grams per person per day. Due to different living habits and tastes, the actual intake of salt varies from person to person. China people eat about 10 g ~ 15 g of salt every day.
Edible instructions
First, buy less and eat in time.
Buy a small amount, and then buy it after eating, in case of iodine volatilization. Because potassium iodate will decompose and volatilize under the conditions of heat, light, wind and humidity.
Second, avoid high temperature.
Avoid putting iodized salt at high temperature when cooking soup. The edible rate of iodized salt in cooking and frying is only 10%, and the intermediate edible rate is 60%. The edible rate of iodized salt during cooking is 90%; The edible rate of cold iodized salt can reach 100%.
Third, avoid prolonged exposure to containers.
Iodized salt is easy to volatilize if it is exposed to sunlight and air for a long time. It is best to put it in a colored glass bottle and seal it tightly with the back cover.
Fourth, avoid adding vinegar
The combination of iodine with acidic substance will be destroyed. According to the test, if vinegar is added during cooking, the consumption rate of iodine will decrease by 40% ~ 60%. In addition, when iodized salt meets acidic vegetables (such as sauerkraut), the consumption rate will also drop.
Matters needing attention
Excessive salt can cause cataracts.
Australian researchers have found that if the salt content in food is too high, the possibility of developing cataracts will increase. Cataract refers to the whitening of the lens of the eye, which may lead to blindness if left untreated.
Dr. Robert G. robert cummings of the University of Sydney and his colleagues found that people with the highest sodium intake were twice as likely to suffer from post-posterior subcapsular cataract as those with the lowest sodium intake, which is the most damaging cataract to vision. Their research report was published in the recently published American Journal of Epidemiology.
The researchers examined the eyes of about 3000 adults aged 49 to 97, and asked them to fill out a questionnaire about the frequency of eating. 160 people suffered from posterior posterior subcapsular cataract, and 970 people suffered from one of the other two cataracts unrelated to sodium intake.
The study also found that people with high salt intake may suffer from other cataracts, such as diabetes or hypertension, and may take corticosteroid anti-inflammatory drugs. [2]
Advantages and disadvantages of salt to human beings
Usually, the concentration of water in human tissues is 0.9%, that is, 100 ml of water contains 0.9 g of salt.
Salt is not only an indispensable condiment in people's diet, but also an indispensable substance for human body. Its main component is sodium chloride, which is a neutral inorganic salt. It is salty in taste and cold in nature, and enters the stomach, kidney and large intestine. Has the effects of clearing away heat and toxic materials, cooling blood, moistening dryness, invigorating kidney, relaxing bowels, killing parasites, diminishing inflammation, inducing vomiting and stopping diarrhea.
"Shennong Materia Medica" records: "Salt is applied to beriberi, cleaning and strengthening teeth, and treating various skin diseases." Washing feet with salt and perilla root soup can cure beriberi. Scrubbing the skin with salt water can make the skin healthy and enhance resistance. Salt has an analgesic effect. If hot water burns your skin, rubbing some salt (or soy sauce) can relieve the pain. Drinking light salt water in hot weather can prevent constipation, sore throat, toothache and abdominal pain. Drinking a cup of salty boiled water every morning can avoid losing your voice If you eat toxic food by mistake, drink some salt and boiled water to detoxify. Milk goes bad easily in summer and autumn. Less salt in milk can prolong the shelf life of milk. Before eating vegetables and fruits, soak them in light salt water for 20 minutes to remove residual pesticides and parasite eggs and kill germs. Wash the fish in salt water before frying, and the fish will have no dirt and smell. In addition, salt can also soften acid lumps in the body.
From a physiological point of view, salt is of great significance for maintaining human health: salt can help people digest food. The salty taste of salt can stimulate people's taste and increase oral saliva secretion, thus increasing appetite and improving food digestibility. Salt can participate in body fluid metabolism. Salt is an important component of body fluids. People who work in high temperature sweat too much and need to supplement their drinks. People with excessive vomiting and diarrhea should be given normal saline; People with excessive blood loss should also drink warm salt water urgently, because salt can maintain the osmotic pressure and acid-base balance of the human body.
In the past, it was foolish to think that salt was a necessary food for human survival. Modern science gave us a loud slap in the face. Salt is one of the killers affecting human health. Excessive salt can cause many diseases. In China, people generally eat too much salt. According to the national nutrition survey, the salt consumption from south to north ranges from 12g to 15g. According to the regulations of the World Health Organization 6g, we have more than doubled. Moreover, eating too much salt has a direct impact on health, so we must control the amount of salt, give priority to light and eat scientifically.
1. Too much salt can lead to hypertension.
According to experts' investigation, there is a certain relationship between salt intake and the incidence of hypertension. The more salt you eat, the higher the incidence of hypertension. Eskimos in Alaska have very low salt content and basically have no hypertension, while residents in northern Japan who have a daily salt content of about 20 grams have a surprisingly high incidence of hypertension. In Guangdong province, where the salt content is low in China, the incidence of hypertension is only 3.5%; However, northerners who like salty food have a significant increase in the incidence of hypertension. This is because under the action of some endocrine hormones, salt can increase the sensitivity of blood vessels to various antihypertensive substances, cause arteriolar spasm, raise blood pressure, and may also accelerate the hardening process of renal arterioles. At the same time, salt also absorbs water. If the salt accumulates too much, the water content will increase greatly and the blood volume will increase accordingly. In addition, the imbalance of potassium and sodium inside and outside the cell will damage the function of red blood cells, and the blood flow will be viscous and slow, which will increase the workload of blood circulation and lead to further increase of blood pressure.
2. Too much salt can cause edema.
Because there is too much salt, sodium accumulates in the body, and sodium is hydrophilic, which will cause edema and increase the burden on the kidneys.
Too much salt can cause a cold.
High concentration of sodium salt has strong osmotic effect, which will affect the disease resistance of human cells. Excessive salt, one is to reduce saliva secretion, so that lysozyme in the mouth is also reduced accordingly, so that the virus has the opportunity to implant in the mouth. Second, due to the infiltration of sodium salt, the defense function of epithelial cells was inhibited and the disease resistance was greatly lost. Cold virus can easily invade the human body through cells that have lost barrier function, so people are prone to catch a cold, and upper respiratory tract inflammation such as pharyngitis and tonsillitis often occurs. Excessive salt can lead to heart disease.
4. Too much salt will damage the heart.
There is such a record in Neijing: "More salt makes the pulse thick and discolored". "The taste is too salty, which hurts the bones and depresses the heart." Too salty makes arterioles contract, which is harmful to the heart. For example, the death rate of heart disease among Hunan residents is four percentage points higher than that of the whole country, which is closely related to the large consumption of pork and salt.
5. Too much salt can lead to gastric cancer.
The places with the largest number of patients with gastric cancer in Japan are Akita Prefecture and Yamagata Prefecture in the northeast. There are also many people suffering from gastric cancer. Akita Prefecture, which has the largest number of patients with gastric cancer, once launched a salt reduction campaign, and the number of people who died of gastric cancer decreased by more than 20%. It can be seen that eating too much salt is a major cause of cancer. There is no carcinogen in salt, but it is easy to destroy gastric mucosa and help carcinogens. In addition, kidney disease and stroke are also closely related to excessive salt.
Therefore, a reasonable diet is 2-5 grams of salt every day. Don't eat salty food at ordinary times, especially for the elderly and infants. You can't give your child food according to the taste of adults, which will damage your child and induce hypertension and myocardial weakness. When cooking for the elderly, try to use spicy spices such as vinegar, chopped mustard and pepper instead of salt to reduce the amount of salt.
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