The maximum range of pH value that human life activities can tolerate.

PH also has a "bottom line". The basic unit of our human life activities is cells, and an adult's body is probably composed of trillions of cells. These cells live in body fluids (mainly blood, tissue fluid and lymph), and normal acid-base balance of body fluids is very important for cells to maintain normal function. In the process of metabolism, cells will produce a large number of acidic substances, such as lactic acid and carbon dioxide, and a small amount of alkaline substances. Although these metabolites are more acidic and less alkaline, the body has a powerful and precise regulation system to maintain the pH balance of body fluids. If everyone wants to know whether his body is acidic or alkaline, he must find out his pH value. PH value is usually used to measure the pH value of body fluids. The pH value is the concentration index value of hydrogen ions in the solution, which is generally between 0- 14. When the pH value is 7, the solution is neutral, and when it is less than 7, it is acidic. The smaller the value, the stronger the acidity. It is alkaline when it is greater than 7, and the greater the value, the stronger the alkalinity. Under normal physiological conditions, the pH value of blood is kept between 7.35 and 7.45, which is weakly alkaline. This pH value is the best pH value for human cells to complete physiological functions, and it is not good to have one point less and one point more. The acid-base balance of human body is very important. If the pH value of human blood is lower than 7.35, acidosis will occur, while if the pH value is higher than 7.45, it is alkalosis. Whether acidosis or alkalosis is serious, it will be life-threatening. So should we regularly check the body's pH to prevent acid-base imbalance? In fact, our bodies have a delicate and complicated design. From the digestive system to the excretory system and then to the respiratory system, the acid-base balance is controlled accurately and is not easy to turn sour. Take the small intestine as an example. Although acid or alkali is not directly produced, the reabsorption of alkali in pancreatic juice can be adjusted according to the composition of food, thus adjusting the concentration of alkali in blood. Small intestine can also maintain acid-base balance by regulating the absorption of alkali ions (such as magnesium, calcium, potassium, etc.). ) on the food. The large intestine can also regulate the absorption of sulfur-containing amino acids and organic acids. Generally, sulfur-containing amino acids and organic acids enter the liver and other organs from the digestive system, and after metabolic reaction, hydrogen ions (acids) or alkali ions are generated and released into the blood. However, our blood is fearless in the face of a large amount of acid and alkali from the liver, because the blood contains several buffer systems such as bicarbonate, phosphate, plasma protein, hemoglobin, oxygenated hemoglobin, etc., and these acids and alkali can not make waves and cause a sharp change in blood pH value. When blood passes through the kidney with metabolites, the kidney will expel acidic substances like a small pump and suck back alkaline substances. At the same time, it will constantly control and adjust the proportion of acid and alkali substances to keep the pH value of the body constant. In addition, one of the final products after the metabolic reaction of sugar, fat and protein in the body is carbon dioxide, which can combine with water to generate carbonic acid, which is the most acidic substance produced in the body; Therefore, our lungs are not idle, constantly discharging carbon dioxide, which is the organ with the highest efficiency in regulating acid-base balance. It is actually quite difficult for the body to be "acidified". From this point of view, under normal physiological conditions, the acid-base imbalance of human body is not easy to occur. Some people claim that "more than 70% of people's physique is acidified, and the pH value of body fluids is below 7.35. These people are in a sub-health state and often feel dizzy, headache, tinnitus, forgetfulness, unreliable sleep, dull skin, mood swings, backache and leg pain, limb weakness, diarrhea and constipation. " In fact, once the pH value of body fluid is lower than 7.35, it is already acidosis, which means a very serious disease. In the early stage of acidosis, symptoms such as loss of appetite, nausea, vomiting and abdominal pain appear. It may be manifested as drowsiness, restlessness and listlessness, leading to coma and death. If you really belong to the so-called "acidic constitution", the most correct choice is to go to the hospital and find a doctor for professional treatment. Acidosis is generally a complication of a certain disease, and its causes are complex and diverse. For example, metabolic acidosis can be caused by peritonitis, shock, high fever, diarrhea, intestinal fistula and acute renal failure, while respiratory acidosis can be caused by meningitis, thrombosis, poliomyelitis, bronchial asthma and extensive lung diseases. In addition, diabetic ketoacidosis is a common acute metabolic complication of diabetes. Without these serious diseases, you don't have to worry about your "acid constitution", and you don't have to take a "home acid-base measuring instrument" for self-inspection every day. According to international practice, the pH of body fluids is mainly measured from four aspects: venous blood, urine, alkali storage in the body and carbon dioxide binding rate. Obviously, these professional tests can not be completed by simple household instruments. There is also an outrageous saying that "acidic constitution" is the root of tumor. Scientists have found that the pH value of microenvironment around solid tumor is indeed lower than that of normal tissues and organs. This is because tumor cells grow faster than normal cells, the blood vessel supply of tumor tissue often can't keep up with the rapid expansion of tumor cells, and the supply of oxygen and nutrients is insufficient. Tumor cells always grow in the microenvironment of lack of oxygen and nutrition, and the metabolic process is different from that of normal cells, which produces more acidic metabolites such as lactic acid and reduces the pH value of tissue fluid around tumor tissues. However, the pH value in tumor cells is the same as that in normal cells. It should be pointed out that the influence of solid tumor on body fluid pH is limited to the microenvironment around tumor tissue. At present, there is no scientific evidence that solid tumors can cause systemic body fluids to "turn sour". There have been medical reports that patients with lymphoma had serious complications of lactic acid poisoning, but this is also very rare in cancer patients. Therefore, "acidic constitution" is not the "pathogenic factor" that induces tumor, but because of the growth of tumor, which leads to the acidification of microenvironment or rare acidosis complications. However, the discovery of acidophilic characteristics of tumor cells provides a new idea for tumor treatment. Scientists are developing alkaline drugs that can kill tumor cells. Acid-base balance after eating Although our body can adjust itself and strictly control the pH of body fluids, it will really "turn sour" only under severe pathological conditions, but we should also pay more attention to our diet to maintain a benign and healthy acid-base balance. Western nutritionists realized as early as the 1920s that diet had an influence on the acid-base balance of human body. The meat, eggs and seafood we usually eat are rich in protein, while protein will produce acidic metabolites after digestion and decomposition in the body, and the products of digestion and decomposition of foods containing starch and sugar such as rice, potatoes, wine and sweets are also acidic, so these foods are acidic. Although many fruits and vegetables taste sour, they are alkaline foods because they are decomposed into alkaline substances in the body. Nutrition research shows that if a large number of acidic foods are ingested daily, acidic metabolites will increase, which will really affect the acid-base balance of the human body. However, our body will not easily turn sour because we eat an extra catty of pork a day, because the pH value of body fluids will be kept in a constant range through the inspection and cooperation of various organs. However, in order to excrete a lot of acidic metabolites, our kidneys will turn around and synthesize more basic ammonia (NH3) to neutralize acidic metabolites, and then excrete them from urine. Therefore, long-term, large-scale and single intake of acidic food will increase the load of the kidney, and weaken the ability of the kidney to excrete acidic metabolites with the increase of age, and finally affect the acid-base metabolic balance. So eating more alkaline food, that is, vegetables and fruits, is good for your health. Especially for the elderly with cardiovascular diseases and diabetes, we should pay more attention to diet, because both thrombosis and diabetes have the potential danger of causing acidosis. Those alkaline health care products, let's look at the ingredients of alkaline health care products. For example, there is a kind of Jiakebao capsule, and its ingredient is chitosan. In fact, we are no strangers to it-the main component of our nails is chitosan. The legendary chitosan can not only improve acidic constitution, but also reduce weight, blood fat, blood pressure, blood sugar and immunity. However, scientists' research shows that chitosan is not so magical, for example, it has no effect on losing weight, lowering blood fat, lowering blood pressure and lowering blood sugar; There is also a lack of scientific evidence to improve "acidic physique". There are also some alkaline health products, which are claimed to be active organic bases extracted from plants-since they are plant extracts, it is more natural to eat fresh vegetables and fruits directly, and the absorption of various alkaloids is more economical and safe. There are also some health care products under the banner of the United States and Australia, so are imported health care products more credible? In fact, in foreign countries, health care products are also sold, and various advertisements are flying all over the sky. However, all health products sold in the US market are marked with a sentence: the efficacy of this product has not been certified by the US Food and Drug Administration (FDA). However, there is a long explanation behind: people think that this product can help improve XXX symptoms and so on. In other words, the efficacy of these health care products has not been scientifically proved; The effect of health care products is more like a placebo, believe it or not.