The team of scientists from the University of Wisconsin-Madison and the Morgridge Institute for Research believe the ‘tremendous’ range of metabolic health information contained in our urine could herald a new revolution in health monitoring and personalisation of nutrition and medicine.
Led by Professor Joshua Coon and Ian Miller, the team noted that urine contains a ‘liquid history’ of an individual's nutritional habits, exercise, medication use, sleep patterns and other lifestyle choices – with metabolic links to more than 600 human conditions, including major conditions like cancer, diabetes and kidney disease.
Coon, who runs the US National Center for Quantitative Biology of Complex Systems, said the idea of meta-scale urine testing has intrigued him for some time.
"Josh mentioned this at a group meeting one time and it was met with laughter," commented Miller. "I thought, you know, I kind of like the idea. I already track a lot this stuff in my everyday life."
"So we went out and bought a couple coolers and started collecting,” Coon added.
A potty idea?
The pair set out with two essential questions: Firstly, can frequent monitoring and testing of urine samples provide useful real-time information about an individual's health? And secondly, can a technology platform be adapted to toilets that can make the collection process simple, accurate and affordable?
Writing in Nature Digital Medicine, they provide date from a pilot study that may offer promising answers to that first question.
The lead investigators collected samples of their own urine over a 10-day period, all of which were submitted for tests with both gas chromatography and mass spectrometry for a complete readout of metabolic signatures.
Collectively they pair provided 110 pee samples over the ten days, but also used wearable technologies to track heart rates and steps, calorie consumption and sleep patterns.
Coon and Miller said the samples contain a ‘remarkable’ health fingerprint that follows the ebbs and flows of daily life.
For example, they noted that in addition to all of the wearable data and urine samples, the two also kept records of coffee and alcohol consumption – finding that urine biomarkers with a known connection to both those drinks were abundantly measured. Further, when one of them took acetaminophen, it was measured in urine by a spike in ion intensity.
The pair also found that metabolic impacts of exercise and sleep could be measured with precision.
From laboratory to lavatory
Coon’s research team is now designing a toilet that will incorporate a portable mass spectrometer that can recognise the individual and process samples across a variety of subjects.
The scientists plan to install the toilet in their research building and expand the user group to a dozen or more subjects.
"We know in the lab we can make these measurements," said Coon. "And we're pretty sure we can design a toilet that could sample urine.”
“I think the real challenge is we're going to have to invest in the engineering to make this instrument simple enough and cheap enough. That's where this will either go far or not happen at all."
He noted that while the mass spec small molecule analyses are currently being done on $300,000 machines, portable mass spec technologies exist at a tenth of that cost.
Indeed, he suggested that with a market so big, costs of the technology could eventually hit a reasonable cost threshold.
"Almost every automobile on the road is more complicated than that portable mass spectrometer," he said.
However, the team conceded that in addition to the technological and economic challenges of building such a device, there are also wide range of ethical challenges in collecting, storing, sharing, and interpreting personalised metabolic information.
“Though these challenges will hinder development of such a biosensor, we present this dataset and an accompanying interactive web-based visualization tool to share our optimism,” the authors said.
“We believe that continuous urine metabolite analysis offers a promising opportunity to integrate with current digital technologies.”
While the pilot study did not look at specific health questions, the team behind the research say many possibilities exist. For example, frequent urine sampling could help show how an individuals metabolise certain drugs, in ways that could be healthy or dangerous. Also, as the population gets older with more stay-at-home care, urine tests would indicate whether medications are being taken properly and having their intended effect.
Coon also believes the ‘smart toilet’ concept could have major population health implications, not unlike the National Institutes of Health ‘All of Us’ human genome database.
"If you had tens of thousands of users and you could correlate that data with health and lifestyle, you could then start to have real diagnostic capabilities," he suggested.
Source: Nature Digital Medicine
Published online, Open Access, doi: 10.1038/s41746-019-0185-y
“Real-time health monitoring through urine metabolomics”
Authors: Ian J. Miller