In survival movies and TV shows, you sometimes see advice to drink your own urine to avoid dehydration. At first glance, this seems logical: urine is mainly composed of water. But in a real-life situation, as The Conversation writes , this method is more likely to worsen the situation than help.
The human body is about 60% water. To maintain the correct balance of fluids and various substances, the kidneys continuously filter blood. About 180 liters of plasma pass through them per day, but almost all of this fluid returns to the bloodstream. Only what the body no longer needs is excreted in the form of urine.
The final composition of urine depends on several factors, including how hydrated your body is, how active your metabolism is, and what you've recently eaten or what medications and dietary supplements you've taken.
Normally, urine is about 95% water. The remaining 5% consists of urea, creatinine, mineral salts, and other substances that the body tries to get rid of.
That's why the answer to the question of whether urine can help with thirst isn't so simple. If a person is healthy and well-hydrated, urine indeed contains a lot of water. However, even in this case, metabolic products that the kidneys have already excreted re-enter the body along with it.
Kidneys at their limit
In an extreme situation, when the body suffers from a lack of fluid, urine becomes significantly more concentrated. The body loses water through sweat and breathing, so the kidneys begin to conserve every drop. As a result, the amount of water in the urine decreases, and the proportion of urea, salts, and other metabolic products increases.
If you drink such urine, the body will receive not only a little fluid but also a large amount of substances it had already tried to get rid of. To excrete them again, the kidneys will need even more water. Therefore, in the long run, this can only intensify dehydration.
Of particular danger is the accumulation of urea and other metabolic products. If their concentration in the body becomes too high, they can have a toxic effect, especially on the nervous system. In severe cases, this is accompanied by nausea, vomiting, seizures, itching, confusion, and without medical help, can be life-threatening.
Is urine sterile?
There's another problem. Although urine formed in the kidneys usually does not contain bacteria, as it passes through the bladder and urethra, it can pick up microorganisms that naturally live in the urinary tract.
By drinking such urine, a person reintroduces these bacteria into the body. Under normal conditions, stomach acid destroys many of them. But in a survival situation, when dehydration, heat stress, and poor nutrition weaken the intestinal protective barrier, the risk of bacteria entering the bloodstream increases. This can pave the way for serious, and in the worst case, fatal infections.
Therefore, experts do not consider drinking one's own urine an effective way to relieve thirst in extreme conditions. In a situation of severe dehydration, such "water" can do more harm than good.
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