The true face of the world is not always what you perceive from its surface, such as the well-known sour vinegar. The scientific name of sour vinegar is acetic acid, and its molecular formula is CH3COOH. It is an out-and-out acidic substance before it is absorbed and metabolized by the human body. According to the acid-base theory of S. Arrhenius, the so-called acidic substance refers to a substance that dissociates from its aqueous solution or reacts with water to produce more hydrogen ions (H+) than hydroxide ions (OH-). Conversely, if the amount of OH- is dominant, the substance is alkaline. After the acid vinegar is dissolved in water, the generated H+ ions occupy the dominant amount, and it is acidic at this time. If measured by the pH value of acid-base index, the more hydrogen ions (H+), the lower the pH value; The higher the amount of (OH-), the higher the pH value. Generally speaking, all sour substances are acidic. However, nature's nature is magical. This wonderful nature is most concentrated in the metabolism of life. Nature gives life the most complex chemical reaction in the universe, so the original single judgment standard in the natural state becomes no longer single in the living body, which is the process of chemical reaction becoming advanced life reaction. When sour vinegar entered the field of food nutrition from the field of chemistry, it became an alkaline food. Acid/alkaline substance and acid/alkaline food are two different concepts. The pH of acidic/alkaline foods is not necessarily related to the pH of substances before entering the human body. Judging the acidity and alkalinity of food mainly depends on the results of metabolism of basic elements, acidic elements and organic acids contained in food in human body. Usually, the simple judgment method is as follows: all foods with high non-metallic elements such as chlorine, sulfur and phosphorus are acidic because their final metabolites are acidic after being ingested into the human body; Foods with high metal elements such as calcium, potassium, sodium and magnesium are mostly alkaline because their final metabolites are alkaline after being ingested into human body. Kribis, a British scholar, once discovered the "Kribis cycle" (so Kribis won the 1953 Nobel Prize in chemistry). In this cycle, acetic acid entering the human body combines with lactic acid, citric acid and pyrogallol acid in a series of enzymatic reactions, releasing carbon dioxide and water, while carbon dioxide is discharged from the lungs, thus reducing the carbonic acid in the blood and making the body fluid weakly alkaline. After people take vinegar for 2 hours, the urine will become clear. Vinegar can also make people feel delicious to any food, which is also the reason why taking vinegar in moderation can eliminate fatigue, improve the ability to prevent diseases and keep health for a long time. The alkaline contribution of other alkaline foods to human body fluids after entering the human body is similar to this principle. With the popularization of human body fluid pH and health knowledge, people are increasingly aware of the importance of maintaining weak alkalinity of body fluids. The pH value of healthy body fluids is weakly alkaline, about 7.35 (mainly refers to blood). If it is lower than 7.2, the human body will be in a sub-health state, and it is very likely to get various serious diseases-cardiovascular and cerebrovascular diseases, osteoporosis, kidney calculi's disease, arthritis, gout, hypertension, cancer, hyperlipidemia, etc.-acidification of the human body is the source of all diseases. Therefore, people pay attention to those foods/drinks that can maintain weak alkalinity of human body fluids. However, the taste of food often limits people's judgment. Many people attribute sour vinegar to acidic food and dare not eat too much. In fact, like other alkaline foods, the health care function of sour vinegar is very obvious. In addition, like sour vinegar, sour fruit is often misunderstood as acidic food. In fact, almost all fruits contribute to body fluids after human metabolism. Other alkaline foods and drinks include vegetables, milk and high-quality natural water. While people mistakenly regard some sour foods as acidic foods, people also mistakenly classify some acidic foods/drinks as healthy alkaline/drinkable foods, such as preserved eggs and mineral water. Preserved eggs are alkaline before being absorbed and metabolized by human body. But after entering the human body, it is decomposed and oxidized into many acidic substances with sulfur and phosphorus under the action of the digestive system. These acidic substances accumulate in human body fluids, making body fluids sour and inducing various diseases. Mineral water is a very popular drinking water recently. Because of its clever name, people often mistakenly equate it with mineral water. Mineral water and mineral water are two kinds of drinking water with different indexes. Mineral water, like natural water, is a weakly alkaline drink because it contains all kinds of natural minerals needed by human body. However, the metal minerals advertised by mineral water are very different from those in our usual concept. The metal minerals contained in high-quality natural water are the mineral elements in rocks and soil that are slowly dissolved, induced and enriched by water in the natural state, so as to reach a balanced weak alkali level. This is a natural process that is difficult to simulate artificially. However, mineral water is not made of natural water, but is made of pure water (that is, drinking water from which all other substances in the water have been removed by reverse osmosis and other processing means) and artificial mineralized liquid is added. Pure water itself is an acidic drink. This determines that mineral water is inherently acidic. Secondly, as an artificial water, the metal minerals it contains are not natural, but are made by adding artificial mineralizing liquid, such as sulfuric acid. These mineralized liquids contain a lot of nonmetallic elements such as chlorine, sulfur and phosphorus, which are far more than metallic elements. After entering the human body, it produces far more acidic waste than alkaline substances, which will make the human body sour. Therefore, the ultimate destination of mineral water in the field of food nutrition is acidic drinks, rather than alkaline drinks because of minerals as we usually understand. Besides mineral water and purified water, acidic foods/drinks also include meat and carbonated drinks.