Beijing time on January 8, according tomedia reports, in the early 19th century, only the dying people will “condescend” to drink water. As Vincent Presnitz, founder of Hydrotherapy, puts it, only “poor people who can’t be poor enough to quench their thirst”. He added that many people have never had more than a pint (about 500 ml) of white water at once.
But it’s not what it used to be. In recent years, British adults have been drinking more and more water. Sales of bottled water in the United States have also recently outstripped carbonated beverages. We’re constantly bombarded with information that drinking more water is the secret to staying healthy, improving our health and improving our skin, and to help us lose weight and prevent cancer. Whether you are an office worker or a student, you should get into the habit of carrying drinking water with you.
There is an unofficial suggestion called “8 x 8 Law”, recommended that we drink 8 cups of water a day, 240 ml per glass of water, the total amount of water is about 2 liters. But this “rule” is not supported by any scientific research, and neither the UK and EU official guidelines recommend that we drink so much water.
Where does this law come from? Most likely, this comes from misreading of two official guidelines from decades ago.
In 1945, the National Committee of the National Research Council’s Food and Nutrition Commission recommended that each adult should consume the same amount of liquid as the calories he or she consumed. For example, if a woman consumes 2,000 calories a day, she should consume 2 liters of liquid. The term “liquid” here refers not only to water, but also to most drinks and fruits and vegetables, some fruits and vegetables can contain up to 98% water.
In 1974, nutritionists Margaret McWilliams and Frederick Stare suggested eating health. The average person should drink 6 to 8 glasses of water a day. But the moisture can come from fruits and vegetables, decaffeinated soft drinks, even beer, and so on.
Follow the feeling.
The importance of water is indisputable. It accounts for two-thirds of the body’s weight, transports nutrients and waste throughout the body, regulates body temperature, acts as a joint lubricant and shock absorber, and plays an important role in most chemical reactions in the body.
We lose water through sweating, urination and breathing. Ensuring that there is enough water in the body to maintain the balance of body fluids is essential to prevent dehydration. Dehydration symptoms can occur when you lose 1% to 2% of your body’s moisture. If water is not replenished in time, these symptoms will continue to worsen. Severe dehydration can even be fatal.
Over the years, the words associated with the “8-by-8 rule” have led us to believe that when we feel thirsty, it means that the body is severely short of water. But experts generally agree that we just need to drink until we stop thirsty.
“Control of water is one of the most subtle mechanisms the body has evolved,” said Irwin Rosenburg, a senior scientist at the Neuroscience and Aging Laboratory at Tufts University in Massachusetts. The body can ensure adequate moisture in a number of ways. “
In healthy people, the brain detects a lack of water and stimulates thirst, which stimulates people to drink water. The brain also releases a hormone that allows the kidneys to store moisture by increasing urine concentration.
“The body will tell you, ‘I’m thirsty.’ Courtney Kipps, a sports consultant at University College London, said: ‘The reason for the rumour that ‘feeling thirsty means the body is seriously short of water’ is because people default to thirst not being able to accurately judge the lack of water. But since all other mechanisms in the body work with precision, why not be thirsty? Throughout the history of human evolution, this mechanism has worked smoothly for thousands of years. “
Water does not contain any calories and is therefore the healthiest way to ingest water. But other drinks can also rehydrate the body, such as tea and coffee. Although caffeine is beneficial to urine, studies have shown that tea and coffee can still rehydrate the body, as do alcoholic beverages.
The healthier you drink?
There is little evidence that drinking more water has additional health benefits in addition to avoiding dehydration.
But studies have shown that even avoiding the early stages of mild dehydration can have many health benefits. For example, many studies have found that drinking enough water to avoid mild dehydration can help support brain function and the ability to perform simple tasks such as problem solving.
Some studies have shown that ingesting liquids can help manage weight. Brenda Davy, a professor of human nutrition, food and kineity at Virginia Tech, has conducted several studies to examine the relationship between fluid intake and weight.
In one study, she divided the subjects into two groups. Both groups were required to eat on a healthy diet for three months, but she asked one group to drink 500ml of water half an hour before meals. As a result, one group asked to drink water lost more weight than the other.
In addition, both groups of subjects had a 10,000-step day walk, but more people who drank more water were better able to stick to it. David speculates that this is because 1-2% of mild dehydration is so common that many people may not be aware at all. And even a slight degree of dehydration can affect our mood and physical fitness.
But Barbara Rolls, professor of intensive care medicine at University College London, points out that these weight loss may seem to be related to drinking water, but more likely to be due to the fact that subjects replaced sugary drinks with water.
“The theory that drinking water before meals can help you lose weight has not been proven, and the water you drink will soon be drained out of the body. But if you get more water through foods such as soup, it can stay with the food for longer in the stomach. “
There are also claims that drinking more water can improve skin and moisturize the skin. But there is little evidence that there is a sound scientific mechanism behind this.
The water is good, can’t you be greedy for a cup?
If you have to drink eight glasses of water a day, it’s not bad for your health. But if we believe that we must drink more water than our bodies need, it can sometimes backfire.
Eating too much fluid can lead to lower levels of sodium in the blood, which can lead to cerebral edema and pulmonary edema.
In the past decade, Kipps has heard of at least 15 incidents in which athletes have died from overwatering while competing. She suspects this is because we don’t trust our thirst mechanisms and always think we need to consume more water than our bodies suggest.
Johanna Pakenham took part in the 2018 London Marathon, the hottest marathon ever held. But she was not impressed by the race because she drank too much water on the way, causing hyponatremia and had to be rushed to hospital.
“My friends thought I was dehydrated and let me drink a big glass of water. As a result, I began to spasms violently and then went into cardiac arrest. I was taken by helicopter to hospital, where I was in a coma from Sunday night until the following Tuesday. “
She points out that the only advice her friends and marathon posters give her is to “drink plenty of water.”
“I actually just had to take a few electrolyte supplements to raise my blood sodium levels and I was safe. I’ve run a few marathons before, but I don’t know anything about it. “
How much is the best drink?
We have to keep our bodies hydrated at all times, which means we carry water with us wherever we go and we need more water than our bodies need.
“In the middle of the hottest desert, a person loses 2 litres of water through sweat in an hour. But this is generally difficult to happen. Hugh Montgomery, director of the London Institute for Sport, Sport and Health, points out, “So there’s no need to bring a big bottle of water for a 20-minute subway ride, even if you’re sweating, you don’t need to add that much.” “
The NHS, the UK’s official medical institution, recommends drinking six to eight cups of liquid a day, including skimmed milk and sugar-free drinks such as tea and coffee. It is also important to note that after the age of 60, the sensitivity of the body’s thirst mechanism is significantly reduced.
“As you get older, the body’s natural thirst mechanism becomes less sensitive, making it more likely to be dehydrated than younger people. So older people need to pay more attention to their liquid intake and keep their bodies hydrated. “
Most experts agree that everyone’s need for fluid intake depends largely on factors such as age, size, gender, environment, and exercise.
“One of the problems with the 8×8 rule is that it oversimplifies the body’s response to the surrounding environment,” Rosenberg said. “
Most experts agree that we don’t need to worry too much about “how much water we have to drink” every day. Once the body feels thirsty, it sends a signal, just as we feel hungry or tired. The only health benefit of drinking more water seems to be just the calories you burn by running the toilet.
What are the symptoms of dehydration?
Dehydration means losing more liquid than ingesting. According to the NHS, symptoms of dehydration include darker urine, fatigue, heavy head and feet, dry mouth, lips and eyes, and less than four urination slots a day. However, the most common symptom is simply feeling thirsty.