In 1974, nutritionists Margaret McWilliams and Frederick Stare co-authored Nutrition for Good Health, which recommended that adults drink an average of six to eight glasses of water a day, but the authors believed this should include fruits, vegetables, caffeine, beverages even beer.
Believe in thirst
Water is important, accounting for about two-thirds of our body weight, transporting nutrients and waste products throughout the body, regulating body temperature, acting as a lubricant and shock absorber in joints, and playing an important role in most chemical reactions in the body.
We lose water when we sweat, urinate and breathe. Ensuring that the body is well hydrated can prevent dehydration. Dehydration occurs when the body loses 1-2% of its water content and will continue to worsen if not rehydrated. In rare cases, dehydration can be fatal.
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The unproven “8-by-8 rule” leads us to believe that feeling thirsty means we’re in a dangerous state of dehydration. But experts say that when our bodies signal that we don’t need to take in too much water, it’s okay to do so.
“Hydration is a complex function that has evolved since humans evolved from the sea to the land. The human body has many sophisticated ways to stay hydrated.” says Irwin Rosenburg, a senior scientist at the Neuroscience and Aging Laboratory at Tufts University in Tufts, Massachusetts.
Drinking water
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A healthy body signals thirst when the body is dehydrated
In normal health, the brain detects when the body is dehydrated and reminds people to drink water through the sensation of thirst, while also releasing a hormone that tells the kidneys to save urine to stay hydrated.
“If you listen carefully, the body will tell you when it’s thirsty. If you listen carefully, the body will tell you when it’s thirsty,” said Courtney Kipps, a consultant sports medicine physician. He is director of clinical teaching in sports medicine, exercise and health at University College London and medical director of the Blenheim and London Triathlons.
“The assertion that it’s too late when you feel thirsty is based on the assumption that thirst is not a good indicator of insufficient body fluid. Why is it that everything else in the body is accurate, but only thirst is a problem? The thirst mechanism has been working well for thousands of years of human evolution.
Water is calorie-free and is the healthiest choice, but other beverages can also hydrate our bodies, including tea and coffee. Although caffeine has a slight diuretic effect, studies show that tea and coffee still help with hydration, as do alcoholic beverages.
Open a glass of champagne
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Water is the healthiest choice, but tea, coffee and even alcoholic beverages can all be hydrating
Drink your way to health
Aside from avoiding dehydration, there is little evidence that drinking more water than your body needs has other benefits.
However, studies have shown that starting to drink water in the early stages of mild dehydration does have an effect. For example, many studies have found that avoiding mild dehydration by drinking water helps to enhance brain function and improve the ability to complete simple tasks such as problem solving.
Some studies have shown that fluid intake can help control body weight. Brenda Davy, a professor of human nutrition, food and exercise at the Virginia Polytechnic Institute and Virginia State University, has conducted studies on fluid consumption and body weight.
In one study, she randomly divided the subjects into two groups. Both groups were asked to follow a healthy diet for three months, but only one group was required to drink 500 ml of water half an hour before a meal. The results showed that the group that drank water lost more weight than the other group.
Both groups of subjects had to walk 10,000 steps a day, but the group that drank water lasted longer. David speculates that this is because a mild dehydration of about 1-2% is common and many people may not even be aware of it, but even this mild dehydration can affect our mood and energy levels.
But Barbara Rolls, professor of critical care medicine at University College London, says drinking water to lose weight may be because water replaces sugary drinks.
“The idea that drinking water before meals can reduce weight is not true, because the water you drink will soon be expelled from the stomach. But if you take in more water through food, such as soup, you will feel full because the water stays in your stomach longer when combined with food,” she said. She said.
Drinking water
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Many people are mildly dehydrated, they just don’t know it
Another health benefit of drinking more water is said to improve skin tone and moisturize the skin, but there is no scientific evidence for this claim.
The opposite is true
Drinking 8 glasses of water a day is not harmful to your health. However, sometimes the idea that you must drink more water than your body needs can be harmful.
Too much fluid intake can dilute sodium in the blood, which can lead to swelling of the brain and lungs, which can be dangerous. This is because body fluids will shift themselves to balance the sodium level in the blood.
In the last 10 years or so, Kipps has found that at least 15 athletes have died from overdrinking during sports events. She believes part of the reason is that we don’t trust the thirst response and think we need to drink more water than our bodies need to avoid dehydration.
Nurses and doctors in hospitals come across patients with severe dehydration, or who have not been able to drink for days, but these are very different from the dehydration people worry about during marathons,” she said.
Exercise and Drinking Water
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Many people don’t know this, but too much fluid intake can be dangerous
Johanna Pakenham ran the 2018 London Marathon, one of the hottest on record, but she doesn’t remember what happened when she drank so much water during the race that Pakenham became overhydrated, also known as “hyponatremic. Later that day, she was rushed to the hospital.
“My friends and partner thought I was dehydrated, so they gave me a large glass of water. After that, I started to go into full-body spasms and my heart stopped beating. I was then taken to the hospital by ambulance helicopter and was in a coma from Sunday night until next Tuesday,” she said.
Packenham, who is also planning to run a marathon this year, said the only health advice from friends and marathon posters is to drink more water.
“I just need to take a couple of electrolyte tablets to raise the sodium level in my blood. I’ve run a few marathons before, but I didn’t know that at the time,” she said. I really wanted to tell people.
“I really want to tell people that something so simple can be deadly.”
How much should I drink?
The idea that “we must always hydrate” means that many people carry water with them wherever they go, and drink more than their bodies need.
Hugh Montgomery, director of research at the Institute for Sport, Exercise and Health in London, said, “A person sweats 2 liters per hour in high desert temperatures, but that’s really hard to come by.
“You can take the London Underground for 20 minutes with 500ml of water and not sweat as much as you would in the desert.
The NHS recommends that for those who don’t feel thirsty even if they don’t follow the official guidelines for drinking water, they should drink six to eight glasses of fluids a day, including low-fat milk, sugar-free drinks, tea and coffee.
