Drinking water is not a "little thing"

 　　In a documentary, the explorer Bell and his party are in the hot South African savannah, which has exhausted its freshwater reserves. Just when the crowd was dry, Bell looked at the elephant group not far away, thoughtful. He approached the elephant herd, held up a pool of green, sticky, and hot elephant dung, like a treasure, and then faced the camera and said: "The digestion process of elephants is very fast, and a lot of water in plants is not absorbed. It will be excreted along with the excrement." After speaking, he held up the elephant excrement, raised his head, opened his mouth, and drank the "soul soup" squeezed out of the excrement.

　　As long as you have a strong heart and don't pick and choose, the water sources in nature are actually very rich. However, if the water source is required to be clean and hygienic, it must live in close proximity to streams and lakes. Therefore, early human civilizations were often established on the banks of rivers. For thousands of years, the territory of human settlements has continued to expand. In order to obtain long-term and stable water supply in areas far away from rivers, human beings have developed a series of water diversion and storage schemes. Ancient Rome is a representative of them.

The ancient Roman aqueduct can supply about 1.45 million liters of water per day, meeting the water needs of about 50,000 people

　　It has been said that if the famous ancient Roman aqueduct, and the showers and toilets built on its foundations, would be less than half the pride of the empire. In 63 BC, the Roman Empire captured a city in the Kingdom of Judah and named it Caesarea. At that time, the city of Caesarea lacked fresh water resources. In order to consolidate the local rule, the Roman monarch ordered the construction of an aqueduct, which led water from a spring 16 kilometers away to the city. Archaeologists today speculate that the installation could supply about 1.45 million liters of water per day, enough to meet the water needs of about 50,000 people. According to statistics, more than ten aqueducts were built in the Roman Empire. Aqueducts nourished the ancient Roman Empire and created a colorful ancient Roman civilization.

Why are humans so thirsty?

　　Humans do their best to drink water, but animals seem to be far less fond of drinking water than humans, and they can withstand much more water loss than humans. Why are humans so thirsty? The answer to this question is hidden in the early evolution of human beings.

　　Millions of years ago, the climate of Africa, the "homeland" of mankind, became extremely dry. Climate change caused grasslands to replace forests, and human ancestors gradually became adept at walking upright in open environments at the cost of being tired and hot. In order to improve heat dissipation and maintain a healthy body temperature, hominids lost most of their hair and developed more sweat glands. With this powerful "cooling" system, human ancestors had greater exercise endurance than other primates, and could hunt for long periods of time without overheating. However, well-developed sweat glands also come with a downside: "We" are more prone to dehydration due to constant perspiration. Therefore, the drinking water requirements of humans are significantly higher than those of other mammals.

Developed sweat glands allow the body to lose water quickly

　　In a water-deficient environment, animals have evolved various "emergency measures". The kidneys of the guinea pigs allow for a high degree of urine reflux, and they can make do without a drop of water for months; the camel's stomach can store a lot of water and use it for weeks. Humans don't have any of these skills - no matter how thirsty, people's urine output is almost a lot; drinking a lot of water, and can't save it for a rainy day, will only make us run to the toilet frequently; even worse, if Drinking too much water too quickly may break the body's water-salt balance, which is even more harmful than dehydration. Therefore, if you love to drink water, you must drink it properly.

Do you want to drink water or not, listen to what your body "says"

　　You may have heard of appearance anxiety and academic anxiety, but have you ever heard of "drinking water anxiety"? We are always inadvertently told by various sources: Drinking enough × × milliliters of water every day is the secret to staying healthy; losing weight depends on drinking water, nourishing your face depends on drinking water, and preventing cancer depends on drinking water... For such " Popular science", some people are convinced that once the inaccurate so-called "daily recommended water intake" is not reached one day, the whole person will feel bad.

Drinking water at the right time is human instinct

Drink water reminder

　　In order to relieve anxiety about drinking water, more and more people start to use mobile apps to remind themselves to drink water regularly. Even if they are not thirsty at all, they should fill their stomachs with water, and they will not give up until the task of drinking water on the day reaches the standard. The "recommended daily water intake" was first proposed by an unofficial organization in the United States in the 1940s, which recommended that adults drink at least 1.9 liters of water a day. In the 1970s, this indicator was simplified by some nutritionists as "6 to 8 glasses of water a day". However, no matter which of the above descriptions, there is no evidence to support it. Instead, there is a growing body of research showing that the body's signals are the best commands for judging whether you need to drink water.

　　In an experiment to study the feeling of thirst, scientists invited 19 volunteers to continue exercising until the volunteers were sweating profusely, their thirst became unbearable, and their body weight dropped by 1% due to perspiration, the scientists motioned the volunteers to lie down In an MRI machine, they were given water to watch while their brains responded. At first, the volunteers' brain signals were calm, and when they were no longer thirsty, but continued to drink water according to the experimental needs, interesting things happened. The cerebral cortex that turned on the "swallowing" action became calmer, which meant that the volunteers needed to mobilize their organs to drink water more deliberately and harder; on the contrary, the cerebral cortex that inhibited the "swallowing" action became more active.

　　A variety of phenomena tell us that the brain is very good at regulating the feeling of thirst. For a long time, there has been a popular saying that thirst is a sign of dehydration in the body, and it is too late to drink water when you are thirsty. The truth is, if the body doesn't need to be hydrated, the brain won't make you feel thirsty, and it's counterintuitive to drink water when you're not thirsty. From an evolutionary perspective, the area of ​​the brain that governs this physiological mechanism is very ancient, and it's dedicated to one thing: getting you to not drink too much water. This mechanism has worked well for thousands of years, has it changed in just a few decades? In addition to thirst, the body sends other signals to hydrate. For example, the color of the first pee in the morning is very telling. If a person does not drink enough water for a long time, the color of the urine will deepen; when you wake up, your mouth will be dry, which is also a precursor to dehydration. So instead of listening to "tips" that have no scientific basis, listen to what your body "says".

　　Although the "daily recommended water intake" is ineffective, it is also correct most of the time and will not harm the body. In some cases, such as drinking a lot of water in a short period of time after heavy drinking or strenuous exercise, the kidneys may not be able to urinate in time, resulting in an abnormally low concentration of sodium in the human blood, resulting in hyponatremia. Symptoms of the disease include nausea, vomiting, irritability, muscle weakness, etc., and even life-threatening in severe cases. The marathon is held every year in London, England, and the weather in 2018 was the hottest since the event was launched. According to one contestant, she still had a fresh memory of that competition, because she went to the "Ghost Gate" for a while. Shortly after the run, she was sweating profusely due to the scorching heat. A friend was afraid that she would be dehydrated and handed a large bottle of pure water. She took the water bottle and started drinking as she ran. A few minutes later, she fell to the ground, unconscious. Fortunately, after rescue, she finally woke up.

Drink water, you don't need to fix all those bells and whistles

　　Today in the 21st century, people's enthusiasm for health betting is unprecedentedly high. Drinks such as soft drinks and juices have long been labeled as "fat house happy water" and "carb bomb". When thirsty, pure water is the first choice for many people. . However, there are always merchants who are "broken" for human health. They feel that pure water is not good enough, so they launch alkaline water, oxygen-enriched water and other seemingly "high" drinking water, trying to "let your body Good addition to good." Dazzling advertising, is it true? Where does the choice of healthy drinking water go?

　　About ten years ago, there was a kind of "oxygen-enriched water" that was quite popular. As the name suggests, oxygen-enriched water is rich in oxygen. "Oxygen is essential to life. As long as the brain is deprived of oxygen for a few minutes, it will suffer permanent damage. Therefore, the more oxygen, the better!" The above argument is a common marketing rhetoric for oxygen-enriched water manufacturers. These businessmen often target athletes as their primary audience, telling them that "oxygen-enriched water can help improve athletic performance." is this real?

　　First of all, it should be clear that as long as the water comes into contact with the air, the oxygen in the air dissolves into the water. Although the amount of dissolved oxygen in the water is very small, it is these trace amounts of dissolved oxygen that fish live on. By means of pressurization, more oxygen can be dissolved into the water, which is also the consistent practice of oxygen-enriched water manufacturers. However, the larger amount of dissolved oxygen can only be maintained in a water bottle with higher air pressure; at the moment when the water bottle is opened, the air pressure drops sharply, and most of the oxygen escapes immediately. Pretty much the same.

　　So, is it scientific to drink water to supplement oxygen? According to statistics, the average adult inhales about 100 milliliters of oxygen per breath, and if the oxygen in every 100 milliliters of oxygen-enriched water is fully released, the average is only about 10 milliliters. Even if 100% of the oxygen in the water can be absorbed by the human body, drinking a full liter of oxygen-enriched water will only absorb as much oxygen as breathing once. Besides, we don't breathe through our guts at all. Little of the oxygen carried by the diet enters the bloodstream through the intestinal wall. It can be seen that "oxygen-enriched water has miraculous effects" is purely self-promotion.

Drink a full liter of oxygen-enriched water, and the oxygen intake is only about the same as breathing once

Even being jealous doesn't affect blood pH

　　Looking at the current market, "alkaline water" seems to have replaced oxygen-enriched water and become a frequent visitor on supermarket shelves. Manufacturers' gimmicks are often like this: "People eat too much acidic food, and their constitution is acidic, and acidic constitution is the root of all evils such as obesity, osteoporosis, diabetes and hypertension. Therefore, we need to drink some alkaline Water to neutralize." This statement really does not stand up to scrutiny.

　　First, there is indeed a theory of blood acid-base balance in medicine, but the word "acid-base constitution" is nonsense. There are many acid-base buffer substances in our blood that keep the pH of the blood stable with minimal fluctuations. Not to mention drinking commercially available alkaline water, even if it is slightly more acidic "water" such as vinegar, drinking two sips will hardly affect the pH of the blood. If drinking some alkaline water will significantly change the pH of the blood, then people may not be able to live normally. Second, after drinking alkaline water, its alkalinity will be immediately neutralized by the extremely acidic stomach acid. Moreover, the main organ that absorbs water in the human body is the small intestine, and the digestive juice secreted by the pancreas into the small intestine will alkalize food and water. In this way, is it necessary to buy alkaline water at a high price?

　　The "Dietary Guidelines for Chinese Residents" promoted by China points out that eating acidic or alkaline foods has little effect on the human body, and it will not lead to acid-base poisoning.

Drink pure water, but not too pure

　　In midsummer, nothing is more soothing than a glass of cold pure water. It is well known that drinking untreated water directly carries certain health risks. Waterworks and drinking water suppliers work together to remove harmful substances such as parasites, impurity particles and excess minerals from natural water sources. So, does this mean that the purer the drinking water, the better?

　　In the laboratory, scientists often use "ultrapure water" when conducting chemical experiments. That is because the water contains impurities, which will affect the experimental results through chemical reactions, so it must be pure, and the purer the better. Ultrapure water is water that is so pure that it hardly contains any impurities. It is true that the water molecules that make up ultrapure water are non-toxic, and people will not feel any discomfort after drinking one or two sips of ultrapure water. However, long-term use of ultrapure water as drinking water is actually more harmful than beneficial. This is because repeated purification treatment has removed most of the ions that are beneficial to the human body in the water body, and people cannot obtain trace elements by drinking water. The only function of drinking ultrapure water is to replenish water, and because there are almost no solutes in ultrapure water, ultrapure water is more soluble than ordinary water, and nutrients in the human body are easily taken away by water and lost to the body - do you think It's you who's drinking the water, it's actually the water that "drinks you".

Scientists are receiving ultrapure water

　　Drinking water is a common and common thing, once you dig deep, it is also very particular. However, you don't have to worry about drinking water because of this. Just remember, don't be fooled by internet gossip and marketing hype. The "little thing" of drinking water is true.