Urine

Urine is liquid metabolic waste, typically yellow in color, which comes out of the human body from the bladder through the urethra. It is made by the kidneys, travels through two small tubes called ureters, and is then stored in the bladder. A typical adult bladder can hold about 400–600 milliliters (roughly 1.7–2.5 cups) of urine, though this varies depending on individual factors. Urine contains the body’s extra water and salt and nitrogen compounds that are filtered by the blood and the kidneys. Much can be determined about a person’s health by the color, pH (acidity), density, and odor of their urine. The frequency of a person’s urination can also give health care providers insight into a person’s health. Various tests can be run on a person’s urine to determine illness or what is going on in the body. The most common test is a urinalysis, which analyzes urine based on its physical and chemical makeup. Urinalysis is also used to help detect early signs of kidney disease, diabetes, and other chronic conditions. A urinalysis can determine different scenarios, such as if a person has a urinary tract infection or if a person has been using drugs.

Urotherapy, or urine therapy, the practice of using one’s own urine or another person’s urine for medicinal or cosmetic purposes, is a topic that has long been debated in the medical community. Health experts say that urine is not sterile and should not be drunk or applied to the skin to bring about health.

Brief History

Historically, urine has had many different uses. When urine sits for long periods, it decays into ammonia. Because of this feature, it was used to clean clothing and soften animal hides. The ancient Romans often collected urine in the streets, and it was taken to places where laundry was done and poured over dirty clothing. Early European people also used urine to get stains out of clothing.

Another historical use of urine was in the production of gunpowder. To make gunpowder, there are a few things needed: charcoal and sulfur in small quantities and potassium nitrate, which was not manufactured on a large scale until the early twentieth century. Historically, urine was used as a source of nitrogen to produce potassium nitrate, an essential component of gunpowder. Gunpowder makers used urine because of the nitrogen that is naturally found in it. To make potassium nitrate from urine, ammonia from stale urine is mixed with oxygen to form nitrates. These nitrates, which are negatively charged, bind with positively charged metal ions. The substance is filtered and is then considered potassium nitrate. This potassium nitrate was then used as a component to make gunpowder.

Organic chemistry also got its start with urine. French chemist Hilaire Rouelle discovered the organic compound urea when he boiled urine dry in 1773. In 1828, German chemist Friedrich Wöhler created a substance identical to the compound urea by mixing silver cyanate with ammonium chloride. Creating urea from scratch disproved a hypothesis that living organisms were made up of substances different from inanimate objects like rocks or glass. This discovery proved that organic chemicals could be produced in a lab and that humans were a part of nature, not separate from it. This began the field of organic chemistry.

Alchemists, or people who tried to turn metal and other things into gold, spent a lot of time trying to get gold from urine, but this led to other important discoveries. German alchemist Hennig Brand discovered white phosphorus when he distilled fermented urine in 1669.

Overview

In the human body, urine begins forming in the nephrons of the kidneys by filtering blood plasma into the nephrons. This fluid passes through the nephron tube, and the components of it that can be used by the body are reabsorbed into the bloodstream. Some of those components include amino acids and glucose. The rest of the material is considered waste and is stored in the bladder until it is expelled through a process called urination. Most of this waste contains water, almost 95 percent of it, but the rest is made from urea, inorganic salts, creatinine, ammonia, and other materials. This liquid has a pale-yellow color because the material also has pigmented products of blood broken down in it.

Healthy urine should have a pale-yellow color, but the color of a person’s urine can give health experts information about a patient’s health. If a person’s urine is dark yellow, that can indicate that they are dehydrated and do not have enough water in their body. Occasionally, the color of urine can change based on what types of food a person has consumed. Pink urine can be caused by eating beets, and asparagus can change the odor of urine, while greenish urine is more often caused by dyes, medications, or infections. Sometimes the color of urine can help health professionals diagnose diseases. When urine has blood in it, that can be a symptom of many different conditions. If urine is dark orange or a brown color, it could be a symptom of jaundice, which is a yellowing of the skin due to an increase of bilirubin in the body. Dark orange or brown urine could also be a symptom of Gilbert syndrome, a genetic liver disorder that causes an increase in bilirubin in the body.

There is other information that is available to health care professionals based on the makeup of urine. The volume and color tell about hydration levels. Elevated white blood cells can indicate a person has a urinary tract infection.

Contrary to widespread belief, urine is not sterile. Research confirms that urine contains a small community of microorganisms, known as the urinary microbiome, even in healthy individuals. This myth has roots in the 1950s, when Edward Kass, an epidemiologist, was searching for ways to test patients for urinary tract infections before performing surgery on them. He created a urine test that obtained urine midstream and set a numerical cutoff for the number of bacteria in healthy urine: not more than 100,000 colony-forming units per milliliter of urine. If the bacteria count was below this amount, the patient tested negative for bacteria in the urine. This led people to believe that there were no bacteria in urine, not understanding that the number just needed to be below a certain threshold, leading to the myth that urine is sterile.

Bibliography

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