In the film Balas e Bolinhos 3, the character John Rato begs his companion Tone to urinate into his mouth, at a time when they are lost in the middle of the mountain.
Can drinking your own urine save you even in an emergency situation?
You may have seen someone drinking urine to save their lives in films, which could lead the public to conclude that this is a legitimate and safe survival trick…
But is it really so? In an article, he describes the our urine like “a trash can”.
Fluids make up about 60% of the body’s total weight. To maintain the correct balance of substances in this internal environment, the kidneys continuously filter around 180 liters of blood fluid (plasma) every day.
Fortunately, we don’t urinate 180 liters of urine, because the kidneys “return” or reabsorb about 99% of what they filter back into the bloodstream.
The best way to imagine this process is to think of a messy garage. If we went through and removed just the unwanted objects, we would stay there all day. A more efficient method is to empty everything into the garage, put away what’s important and throw away the rest. The kidneys use the same strategy.
They ignore the large cells and proteins and filter the plasma part of the blood, which is the equivalent of completely emptying the garage. They then selectively return useful substances to the bloodstream. What is left behind becomes urine, the physiological waste bin.
The final content depends on a few factors, including hydration status, metabolic activity, and recent diet (including medications and supplements).
Normally, urine is about 95% water. The rest is:
- urea (about 2%, a byproduct of protein degradation, which we’ll come back to shortly)
- creatinine (about 0.1%, a byproduct of muscle metabolism)
- salts and proteins.
So, does urine hydrate? Is it safe?
The answer is… yes and no. The answer isn’t always clear because, as we saw above, what’s in our urine depends on what was in the garage.
If we are well hydrated and healthy, our urine will probably be clear or straw-colored, meaning it is mostly water (but will still contain urea, salts and other waste products). Drinking this “first pass” urine will, in fact, provide some degree of hydration.
But in extreme survival scenarios we would be losing water from the body through other means. For example, we would lose about 450 milliliters per day through skin perspiration and about 300 mL per day through water vapor in our breath. In a hot and humid environment, these volumes would increase significantly.
As a result, the kidneys would have to work harder to retain water precious and keep it in the blood. This would further concentrate excretion productsand what would end up in trash can would be quite toxic for our body.
Thus, when drinking urine in a survival context, we would be consuming higher concentrations of excretion products, including urea, which our body explicitly intended to eliminate.
When drinking urine with higher concentrations of waste products (and/or if your kidneys are compromised), urea and other metabolic waste can accumulate in the body. This can become toxic to cells, particularly those of the nervous system.
This can lead to symptoms such as vomiting, muscle cramps, itching and changes in consciousness. Without treatment, this toxic state (known as uremia) can be fatal..
Is urine sterile?
Toxins are not the only problem.
Although urine leaving the kidneys is probably sterile, the rest of the urinary tract (bladder and urethra) is not. Our bodies are full of resident bacteria that maintain our health and support daily functions — when they remain in their usual location.
Therefore, when urine passes through the bladder and urethra, it can collect these bacteria. Drinking this urine would be reintroduce these bacteria into parts of the body where they don’t belong — particularly the gastrointestinal tract.
Under healthy conditions, stomach acid often kills many of these bacteria. But in a survival situation where dehydration, heat stress or poor nutrition can compromise the intestinal lining, the The risk of these bacteria passing into the bloodstream increases. This can create the conditions for potentially fatal infections.
And that’s the last thing you need while you’re lost in the woods. Good thing Tone didn’t actually give urine to John Rato…
