In recent years, scientists have voiced concerns about a potential source of water pollution: the urine of American citizens. While popular diets have boosted protein intake, Americans consume approximately 40% more protein than the daily recommended amount. One of the side effects of excessive protein is the presence of excess nitrogen in urine. When this potent compound enters the environment, it can cause toxic algal blooms, disrupt ecosystems, and make drinking water unsafe, says Maya Almaraz, a biogeochemist at Yale University and author of a 2022 article on this issue. She and her colleagues have calculated that more than 600,000 tons of excess nitrogen are excreted annually in the urine of Americans due to excessive protein intake.
Redaksiya reports that this is just one example of the many surprising pieces of information urine can reveal about our health and habits. Joshua Coon, a chemistry professor at the University of Wisconsin-Madison, states, "If you're consuming alcohol, there are characteristic molecules in urine. If you're drinking coffee, we can see traces of that." David Wishart, a professor at the University of Alberta, a pioneer in the study of molecules in urine, and who maintains a database of over 3,000 molecules identified in human urine, says that some brain tumors leave their traces in urine even before they can be detected by other means. Advances in fundamental research reveal that "there's gold in that golden liquid."
What can urine tell us? Many people have provided urine in a plastic cup, often on a stick, at a doctor's office or at home. A standard test looks for sugar in urine to diagnose diabetes. Another detects human chorionic gonadotropin, an indicator of pregnancy. These tests work because urine contains metabolites: waste products from the body's daily work of breaking down and building new molecules. Just as household trash can indicate, for example, whether residents are vegetarian, metabolites reveal what's happening inside the body. Wishart says, "If something is going wrong in the body, it tends to concentrate in the urine." Wishart and his colleagues discovered that a panel of 69 metabolites in people's urine could predict who had pre-cancerous polyps in their gut. In 2020, he and his collaborators published a test for 149 different metabolites in urine, aiming for others in the research community to use it to study urine and potentially create new laboratory tests.
Urine is not useful for everything. Michael Snyder, a Stanford genomicist and pioneer in the use of long-term personal monitoring for health, says that urine is not as good an indicator as blood when it comes to many tissues, including muscles and heart tissue. However, it can provide particularly detailed information about what people consume. Snyder says, "It's a good window into diet and supplements." Indeed, in a 2019 study from Coon's lab, which aimed to see if urine could be used for real-time health monitoring, he and his colleagues collected all urine provided by two volunteers over 10 days. They measured over 100 molecules in the urine to track the effects of exercise and nutritional supplements. They found, for example, that levels of molecules associated with muscle breakdown, such as creatinine, increased after exercise. They were also able to identify precise information related to the intake of nutritional supplements.
These studies demonstrate how much information urine can provide about our health. In the future, urine analyses could be more widely used for early disease diagnosis and the development of personalized health strategies.