Modern medicine tells people that water goes with salt, and without salt, water cannot stay in the body. Salt, when exposed to water, breaks down into sodium and chloride ions. Sodium and chloride ions are the main positive and negative ions in the extracellular fluid and maintain the crystal osmolarity required for blood and cerebrospinal fluid circulation. In terms of blood pressure alone, humans have established sophisticated blood pressure regulation mechanisms, and salt alone does not maintain the effective blood pressure required by the body. The cerebrospinal fluid, unlike blood, depends almost entirely on sodium and chloride ions for the maintenance of its osmotic pressure, and the cerebrospinal fluid is renewed 3 to 4 times daily, which forces the body to constantly replenish salt to maintain the cerebrospinal fluid pressure required by the organism. Only with sufficient cerebrospinal fluid pressure can it play a role in protecting and supporting the brain and spinal cord to ensure normal human activity in an upright position. Humans walk upright and eat salt unlike other animals, and humans need to eat salt because they walk upright, or as a result of each other. Why do humans need to eat salt? This seems to be a question often asked by children. Searching the Internet, there are quite a few people who think and are confused. The many explanations are no more than that it regulates the balanced distribution of water in the body, maintains the osmotic pressure inside and outside the cells, participates in the formation of gastric acid, promotes the secretion of digestive juices, and can increase appetite. At the same time, it also ensures the acidity necessary for the action of pepsin, maintaining the balance of acidity and alkalinity in the organism and the normal circulation of body fluids. People do not eat salt or eat too little salt will cause the body’s sodium content is too low, resulting in loss of appetite, weak limbs, dizziness and other phenomena; in serious cases, there will also be anorexia, nausea, vomiting, accelerated heart rate, a weak pulse, muscle cramps and other symptoms. Therefore, salt is an indispensable part of people’s diet. However, except for monkeys (often in semi-standing position) which need to lick sweat from the body hair of their companions to obtain salt, other animals, such as: cats, dogs, lions, leopards …… have no deliberate hobby of eating salt. Why do people need to eat salt when they also have to maintain normal blood circulation? As a neurologist, in more than 20 years of medical practice, I have come to realize that eating salt is related to humans walking upright, i.e., compared to other animals, humans need to eat salt because they walk upright. Modern medicine tells us that water follows salt, which means that salt has some kind of attraction to water, and without salt, water cannot stay in the body. Salt, when it meets water, breaks down into sodium and chloride ions. Sodium and chloride ions are the main positive and negative ions of the extracellular fluid, and they adsorb water molecules to keep the extracellular water and solute in balance. Extracellular fluid is mainly composed of plasma, tissue fluid, lymphatic fluid, and cerebrospinal fluid. Of these, plasma is an important component of blood, i.e., sodium and chloride ions maintain the crystal osmolarity required for circulating blood. Without salt, there is no effective circulating blood; without effective circulating blood, the blood pressure required by the body cannot be formed. It is well known that blood pressure can only be in the normal range to ensure the blood supply required by all parts of the body, especially the blood supply to the brain. The higher the water tower, the greater the required pump pressure, and thus by analogy, if there is no interference from the heart, kidneys, blood vessels and other abnormal factors, the blood pressure required by the human body should be proportional to the height. However, this is not the case, because human blood pressure is also regulated by a variety of neurohumoral factors, so that blood pressure has little to do with uprightness. Studies have shown that cardiac output and peripheral vascular resistance are the two major factors affecting arterial pressure in the body circulation, with the former determined by cardiac contractility and circulating blood volume, and the latter influenced by resistance to arterial caliber, compliance, blood viscosity, etc. The compliance of the aortic wall also affects the level of blood pressure. The effects of these factors are constantly regulated by systemic and local neurological and humoral factors to maintain the dynamic balance of blood pressure, physiological fluctuations, and responses to stress. The acute regulation of blood pressure is achieved mainly through pressure receptors located in the carotid sinus and the aortic arch. The afferent impulses to the receptors increase when blood pressure rises, causing a decrease in sympathetic activity and a rise in vagal tone, thereby downregulating blood pressure. In addition, low pressure receptors located in the atria and pulmonary veins, chemoreceptors in the carotid sinus and aortic body, and central ischemic responses are also involved in the acute regulation of blood pressure. Chronic regulation of blood pressure is achieved mainly through the effect on water balance on circulating blood volume, with the renal regulation of blood volume and the regulation of the renin-angiotensin-aldosterone system playing a major role. Hypertension occurs when all these regulatory mechanisms are not compensated, leading to an increase in systemic small arterial resistance or (and) an increase in circulating blood volume. Although there is a large body of experimental, clinical and epidemiological data confirming that salt metabolism and hypertension are closely related, laboratory and clinical studies have found that altering salt intake and blood sodium levels can only affect blood pressure levels in some, but not all, individuals, so it is believed that the pathogenicity of dietary salt is conditional, with hypertension only occurring in individuals with genetic defects in sodium functioning that make them sensitive to salt intake. In conclusion, in terms of blood pressure alone, humans do not need to eat salt because they walk upright, or they have developed a more sophisticated blood pressure regulation mechanism, and salt alone does not maintain the effective blood pressure required by the body. Humans, in addition to a higher demand for salt from circulating blood, also have a higher demand for salt from cerebrospinal fluid. On the surface of the brain and spinal cord is a layer of water, medically known as cerebrospinal fluid, collected in a dense spinal capsule. The spinal capsule, unlike the walls of blood vessels, extends from the top of the head to the sacrococcygeal area, immediately adjacent to the skull and the inner surface of the vertebrae, and has little ability to regulate contraction and diastole. Cerebrospinal fluid also differs from blood in that the maintenance of its osmotic pressure is almost entirely dependent on sodium and chloride ions. In patients with low cranial pressure, the disease often worsens in the upright position and decreases in the recumbent position. This shows the high demand for cerebrospinal fluid pressure in the upright position and, conversely, the low demand for cerebrospinal fluid pressure in the recumbent position. Although the volume of cerebrospinal fluid in normal adults is about 150 ml, the brain secretes about 500 ml of cerebrospinal fluid every day, and its renewal rate far exceeds that of circulating blood, which forces the body to constantly replenish salt to maintain the cerebrospinal fluid pressure required by the organism. Since the brain and spinal cord are relatively constant, the big variable is the cerebrospinal fluid, therefore, the clinical use of lateral lumbar cerebrospinal fluid pressure to reflect the intracranial pressure, 0.098-0.14kPa (10-14mmH2O) for newborns; 0.29-0.78kPa (30-80mmH2O) for infants; 0.4-1.00kPa (40-100mmH2O) for children; 0.78-0.78kPa (40-100mmH2O) for adults. ); 0.78-1.76kPa (80-180mmH2O) for adults. This shows that there is a large change in cerebrospinal fluid pressure from a recumbent newborn to a crawling upright infant; from a child to an adult, cerebrospinal fluid pressure has a gradual increase with growth and development. The newborn baby cannot eat salt, and only babies over 6 months old need to gradually add salty food; children also eat salt in increasing amounts with age, not exceeding 3g within the age of 3. Adult sweat, tears and blood are salty, but only lotion is not salty, also to adapt to the needs of infants and children’s bodies. The normal reference value of cerebrospinal fluid pressure in adults is 80 to 180 mmH2O, such a wide range, mainly influenced by height and weight, that is, the amount of salt required by the body is related to height. Epidemiological surveys in China have found that the proportion of hypertension prevalence is higher in northerners than in southerners, and also found that northerners eat more salt than southerners, thus blaming hypertension on eating more salt, not knowing that northerners are more taller and larger than southerners, and to maintain higher intracranial pressure, they have to eat more salt. Without eliminating height as an important influencing factor, the conclusion that eating more salt will lead to high blood pressure is obviously unreliable. Although animals do not eat salt and newborns cannot eat salt, the concentrations of sodium and chloride ions in their blood basically fluctuate in the same small interval as adults. This shows that whether herbivores or carnivores, the sodium and chloride ions in food are basically sufficient to meet the needs of the body, while humans have to eat salt daily to meet the pressure of cerebrospinal fluid required by the body after uprightness. Cerebrospinal fluid is constantly produced and absorbed back into the veins, and plays the role of lymphatic fluid in the central nervous system, supplying brain cells with certain nutrients, carrying away metabolites from brain tissue, regulating the acid-base balance of the central nervous system; and buffering the pressure of the brain and spinal cord, which has a protective and supportive effect on the brain and spinal cord, especially in the upright position. If salt deficiency alone would result in inadequate intracranial pressure, then eating salt would solve the intracranial pressure problem. In fact, our spinal capsule is not indestructible, and spontaneous cerebrospinal fluid leakage is inevitable, whether from congenital spinal dysplasia or acquired damage to the spinal membrane. The spinal capsule is like the tire of a car, so fragile and undetectable that clinicians rarely consider this aspect of the problem. Spontaneous cerebrospinal fluid leaks are like a festering hole under a thousand-mile dike, threatening our central nervous system at all times. The clinical features of low cranial pressure due to spontaneous cerebrospinal fluid leak can cause a variety of other symptoms in addition to upright headache and dizziness, such as pain and stiffness at the back of the neck, nausea, vomiting, tinnitus, deafness, blurred vision, and weakness of both lower limbs; severe displacement of brain tissue can even lead to brain herniation and impaired consciousness; acute leakage or combined infection can also cause acute onset of disease, resembling meningitis; long-term cerebrospinal fluid leak can also affect a person’s Long-term cerebrospinal fluid leakage can also affect brain function, resulting in cognitive decline and personality changes. Minor trauma is a common cause. Spontaneous hypocranial pressure due to cerebrospinal fluid leakage was first described by the German neurosurgeon Schaltenbrand in 1938 and was once thought to be an extremely rare condition, but since the 1990s evidence has shown that it is not rare and that it is an important cause of persistent daily headaches, especially in middle-aged and young adults. This is especially true. Patients are likely to be misdiagnosed with migraine, tension headache, viral meningitis, and hysteria, which is a typical experience for many patients with spontaneous hypocranial pressure. Because the majority of physicians have little knowledge of spontaneous hypocranial pressure, and because of the complexity of its clinical presentation and imaging features, the diagnosis may be delayed for months, years, or even decades. When there is a cerebrospinal fluid leak, the cerebrospinal fluid pressure drops, and in response, the body activates a series of compensatory mechanisms to maintain the required cerebrospinal fluid pressure. One of the common compensatory mechanisms is the constriction of the peripheral vasculature and the increase in blood pressure. At the same time, the lack of cerebrospinal fluid pressure stimulates the body to take in more salt to maintain cerebrospinal fluid pressure. More salt may just happen unknowingly, not that humans are salt-obsessed and do not have a feedback mechanism for salt intake. Therefore, for patients with hypertension, the first step is to find the cause, and only when the cause is found can the problem be better solved. Age, atherosclerosis, and cardiac and renal disorders are certainly common causes of hypertension, but with the advancement of human understanding, the deep-seated spontaneous cerebrospinal fluid leakage may also be one of the common causes of primary hypertension. The author believes that measuring blood pressure in the morning before getting up or lying down for more than half an hour can at least mitigate the effect of low cranial pressure on blood pressure. Although many countries in Europe and the United States included salt content in the food control regulations, strictly enforced, the World Health Organization also recommended that human salt intake is controlled at the level of 5-6g per day or less, the Chinese Nutrition Society recommended that the national control at 6g or less, it seems that the view that eating less salt is more Jiankang has become a foregone conclusion. In fact, the relationship between salt and hypertension has never been clearly argued in academic circles, and the voices questioning low-salt policies are unfair to the public’s health have never ceased. the first issue of the American Journal of Hypertension in July 2011 published a comprehensive analysis of seven medical surveys, which showed that the long-standing health promotion of less salt may not be the final word. These investigations involved 6,250 subjects: no conclusive evidence was found linking lower salt intake to lower chances of heart disease, stroke and death. Humans walk upright and eat salt unlike other animals, and humans need to eat salt because they walk upright, or as a result of each other.