Do you really need to drink 8 glasses of water a day? An exercise scientist explains why the kidneys say no


The warmer weather and longer days have inspired reminders to “stay hydrated” and drink eight glasses of water (about two liters) a day.

Not to burst anyone’s water bottle, but healthy people can the of drinking too much water. I am a exercise physiologist, and my research focuses on overhydration and how drinking too much water affects the body. Because water and sodium balance is essential to life, it is extremely rare for people to die for drinking too much or too little liquid. In most cases, the tuned molecular processes in your body are subconsciously taken care of by you.

A high school football player drinks water during practice. Many coaches have stressed hydration in recent years. Darrin Klimek / Getty Images

Water outside, water inside

As spring develops, the challenges of hydration sink schools, sports i work places. These highly marketed hydration challenges serve to cultivate camaraderie and friendly competition to ensure we drink mandatory amounts of water throughout the day.

Hydration andGallon challenges”They support the widespread belief that water consumption beyond physiological needs (or thirst) is healthy.

But this is not the case. Individual body water needs (intake) are mainly based on the amount of water people lose. It mainly depends on the amount of water that each person should drink three factors:

  • Body weight. Older people need more water.
  • Ambient temperature. When it’s hotter, people sweat and lose water.
  • Levels of physical activity. Increasing exercise intensity increases sweat water loss.

Therefore, a “one-size-fits-all” liquid replacement strategy, such as drinking eight glasses of eight ounces of water a day, is not suitable for everyone.

It stays it is not clear where the “8 x 8” water supply recommendation is ve de. Perhaps this two-liter administration threshold stems from a misinterpretation of the original recommendations offered by the American Food and Nutrition Board in 1945 as well as the European Food Safety Authority 2017, which indicates that the recommended daily amount of water includes all drinks plus the moisture contained in the food.

This means that the moisture contained in foods, especially fresh fruits, soft drinks, juices, soups, milk, coffee, and even beer, all contribute to this recommended daily need for water. These guidelines suggest that most of the recommended water content can be achieved without drinking additional cups of normal water.

And, it’s important to keep in mind that while alcohol has diuretic properties – ethanol acts directly on the kidneys to make us pee more – Caffeine drinks, such as tea and coffee, do not increase urinary water loss above the amount of water contained in these drinks.

King’s kidney

Now, you may be wondering why this is so. After all, you’ve heard of a lot of people who need to drink more, more, more.

Because the total balance of body water, or what scientists exercise as homeostasis, is complicated, mammals survive by real-time adjustments to the kidney. That’s why when it comes to hydration, our kidneys are king.

Inside each kidney – we only need one (that is, we are born with a spare, just in case) – is a secret network of water channels aquaporin-2 (AQP-2) which respond to hormone called vasopressin arginine. This is the body’s main anti-diuretic hormone (water retention). It is secreted by the posterior pituitary in response to nerve signals sent by specialists brain sensors which detect subtle changes in the water balance. These specialized sensors are called circumventricular organs.

The kidneys will make molecular adjustments to both underhydration and internal overhydration 40 seconds in response to any disturbance in the water balance. These adjustments are the result of the mobilization armies of the AQP-2 water channels, which have approximately 12 million per collecting duct cell.

That is why when we drink more water than our body needs, above thirst, we must immediately dig up the excess water. Or when we forget our bottle of water during practice, we stop peeing to conserve body water. This rapid action coordinated between the brain, cranial nerves and kidneys it is much more effective and accurate than any phone app, gadget or custom recommendation available.

The hosts of ‘Good Morning America’ faced a challenge on the water. These contests perpetuate the idea that it is good to drink eight glasses of water a day.

Is there anything good to get out of this?

The data suggest that you drink about two liters of water a day reduces the formation of kidney stones in people with a history of kidney stones and decreases the number bladder infections in people with a history of bladder infections.

Improvement a skin, renal function i constipation, with increased water consumption, are not clearly supported by science. Drink extra water alone it does not help children lose weight unless water intake replaces the intake of drinks with more calories, such as soda, or makes people feel “full up”Before meals.

Drinking water can affect the mental state of some people. Some studies report better cognitive performance after increasing water intake; while women with anxiety report compulsive water intake makes them feel better, probably by activating reward circuits which increase dopamine. Lots of schizophrenic patients are compulsive drinkers of water, stating that “voices ”they are told to drink and that drinking water suppresses these voices.

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It should be noted that brain imaging studies confirm that it is excessive drinking unpleasant and requires increased muscular effort to drink with thirst. Our brain tries to discourage excessive consumption of chronic drinks or polydipsia, because “social polydipsia”Causes chronic urine (polyuria), which can cause internal modifications to the plumbing, such as bladder distension, ureter dilation, hydronephrosis, and renal failure.

So, do you need to drink eight glasses of water a day? Unless you’re thirsty, drinking extra water probably won’t offer superior health benefits, but it probably won’t be harmful either. However, if the kidneys could speak, they would say that hydration challenges represent nothing more than highly marketed urine competitions.

Tamara Hew-Butler, Associate Professor of Exercise and Sport Sciences, Wayne State University

This article is republished from The conversation under a Creative Commons license. Read the original article.

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