How much water should I drink? Water balance and hyponatremia

Сколько пить воды бегуну? Nutrition
Severe lack of water leads to dehydration. But is it possible to overdo it with water?

A severe lack of water leads to dehydration. But is it possible to over-water and what harm can come from over-hydration?

“It is necessary to drink N-liters of water per day (the required amount, as a rule, is 2.5 liters, 8 glasses, four buckets, etc.).” This is the sound of an old myth, on the basis of which a considerable number of reminder apps for smartphones and their owners “watching their health” have even been released.

Perhaps only the laziest has not yet learned about the origin of this myth, but recommendations to force fluids into oneself continue to appear. Even when it is already physically impossible. And even if your daily diet consisted of several bowls of soup and fresh vegetables, which in itself is an excellent means of hydration, you are recommended to pour into yourself another two or three liters of clean water “for health.

We get a huge part of the necessary fluids from food. At least 50% of the daily norm is for a person with an office lifestyle. Yes, the body of some other animals does it more efficiently. But there is a different physiology, heat exchange process, sweating and other interesting nuances. Regarding our species, we, of course, need constant water replenishment from the outside.

Required amount of water for the body

How much water should I drink per day or per day? There is a great built-in option for regular people. It’s called thirst. And it works better than any mythical smartphone reminder. There is also another reliable indicator – the color of urine and the number of trips to the toilet. Accordingly, if urine is close to dark yellow in color, the amount of water should be increased to optimize kidney function.

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Many studies find no connection between the amount of water you drink and your overall health. Many do. And both are, as usual, full of irrefutable evidence. The “golden mean” in this case, too, seems to be winning.

In the case that we, as athletes, are most concerned about, all researchers agree on one thing: during physical activity, the amount of fluid intake should be increased. Not to mention training and marathons on hot summer days, when a severe lack of water threatens dehydration and heat stroke. However, it was already clear to us.

The only problem is that the body can absorb only a limited amount of liquid per unit time. It is well known that this amount does not exceed 1 liter per hour (more often – no more than 800 ml). And we can lose with sweat, of course, much more. But there are no effective solutions for this case.

Hyponatremia and hyperhidration

Another, more serious problem is hyponatremia (water intoxication), which is caused by “abuse” of water. It occurs when the concentration of sodium ions in the blood is severely reduced, caused by the fact that the kidneys do not have time to process and pass through all the water that has entered the body. To return the blood to the normal concentration of electrolytes and make it more dense, the excess fluid enters the cells of tissues (including the brain), which causes them to swell. And this, as you understand, is already serious.

Fortunately, such cases are not so frequent, because to get hyperhydration you need to drink a large amount of water in a small amount of time.

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At this point, an athlete might think, “Okay, if hyponatremia is a sodium electrolyte deficiency, then maybe an isotonic will solve all the problems?” As the researchers point out, they don’t divide drinks by how likely they are to cause water intoxication.

Hyponatremia symptoms

Overhydration usually results in uncomfortable abdominal bloating, and more serious consequences are indicated by the following signs: nausea and vomiting, headache, short-term memory loss, confusion, lethargy, severe fatigue, loss of appetite, irritability, muscle weakness, spasms or seizures, confusion and coma.

It is important to understand that exactly the same symptoms accompany the opposite state of the body – severe dehydration.

Water Balance

Water balance in the body depends on two factors: water and sodium. When there is not enough water, antidiuretic hormone (ADH) gives the kidneys the order to retain water. At this point, a healthy body begins to feel thirsty.

If thirst is ignored, sodium will continue to draw fluid into the bloodstream from all cells of the body. At the same time, signs of overexertion and irritation will begin to appear. And later on – classic dehydration with possible serious consequences.

How to drink and how much

You should drink water in small sips, remembering that the body is not able to absorb more than 800-1000 ml of water per hour (in women – up to 600-800 ml). During long running or other cyclic physical activity, which contributes to abundant loss of moisture and salts, you can include isotonic drinks with electrolytes. It is better to make your own drinks with pure water.

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Because of the delayed symptoms of lack of water (thirst), athletes need to replenish fluids a little in advance. This has been an axiom of recent years. However, modern experts do not agree with this, and they have not found any deterioration in athletes’ performance during the onset of the feeling of thirst. Contrary to what was previously thought, the body is already dehydrated by the time it becomes thirsty.

Some studies have shown that most normal adults experience chronic dehydration without realizing it themselves. But these studies don’t give a clear picture of the subjects and their lifestyles.

More focused, but unfortunately isolated, studies provide results showing that half of amateur athletes consume insufficient amounts of water. Unfortunately, I was also unable to find information on the conditions of these experiments.

As for the amount of fluid we consume, we have to be guided by the amount we lose by sweating. And that, as you understand, is different for everyone. The safest and most reliable rule when there is no extreme heat is to drink as you feel thirsty (or better, a little before it) and to be guided by the color of your urine. It should remain light straw, not dark yellow.

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