Scientists Can Tell If You’re Eating Healthy by Studying Your Pee

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If you’re like most people, you may have a vague sense of how well you’re doing, nutritionwise — something like “pretty healthy” or “I could be better” — but unless you make all your own food and keep a meticulous diary of what you put in your mouth, you’re probably a little fuzzy on the details. After all, it’s hard to remember every single one of your meals and snacks, and harder still to know everything you’ve been eating and how much of it was good for you, or if your weekday smoothie-and-salad routine is enough to cancel out the weekend junk-food binges. Whether it’s intentionally or inadvertently, people tend to overreport their consumption of healthy foods and underreport unhealthy foods — a big problem for nutrition researchers trying to understand how our bodies respond to what we eat.

But it may not be a problem much longer. At some point down the road, your pee may be able to do the work for you: In a study published last month in The Lancet Diabetes and Endocrinology, scientists described a urine test that identifies chemical compounds that are produced when the body breaks down foods like red meat, chicken, fish, fruits, and vegetables. The test can also reveal how much sugar, fat, protein, and fiber someone has eaten. “We’re not at the stage yet where the test can tell us a person ate 15 chips yesterday and two sausages, but it’s on the way,” said lead study author Isabel Garcia-Perez, a medical research associate at Imperial College London.

For the study, Garcia-Perez and her colleagues developed four diets of varying levels of healthiness, ranging from “healthy” to “unhealthy” when compared to the World Health Organization’s healthy-eating guidelines as a benchmark (the WHO guidelines, as you might expect, call for people to eat more fruits, vegetables, and whole grains, and cut down on sugar, sodium, and saturated fat). The researchers randomly assigned 19 volunteers to one of the four diets, monitoring them closely over the course of several days; urine samples were collected in the morning, afternoon, and evening and analyzed for hundreds of chemical compounds that are affected by the intake of specific foods.

Based on the results, the researchers were able to develop urine profiles for healthy and unhealthy diets. As a next step, they checked the accuracy of the profiles by tracking the diets of, and testing urine samples from, another 291 volunteers — and sure, enough, the urine samples could reliably predict how healthy the volunteers’ diets were.

And the more specific it gets, the greater potential the test has to spur significant changes in nutrition research, particularly studies tracing the link between poor food habits and chronic diseases like obesity, heart disease, diabetes, and cancer. Currently, without a more reliable way to figure out what people are eating, such studies rely on the honesty and memories of their participants — even though research has shown that people misreport their diets at rates ranging from 30 to 88 percent, and that people who are obese are more likely to underreport what they eat.

An objective diet test can also help with the advancement of precision medicine, a relatively new field that designs custom therapies to prevent and treat disease by taking into account an individual’s genes, environment, and lifestyle habits. The last one in particular is hard to monitor in a clinical setting, and yet lifestyle habits play a role in up to half of all preventable deaths in the U.S. each year. If the new test catches on, doctors could use it to screen people for food habits associated with increased disease risk, or to improve compliance with specific diets for patients struggling with obesity or heart disease. “This [test] will eventually provide a tool for personalized dietary monitoring to help maintain a healthy lifestyle,” Garcia-Perez says.

On a larger scale, that can also help institutions develop policies that promote and incentivize healthy habits. Employers and insurers, for example, can fine-tune their programs that reward people for making healthy choices. And confirming what people actually eat could lead to valuable information when it comes to designing public-health campaigns around diet-related diseases.

Of course, the current research is still in its early stages. The urine test needs to be assessed in larger numbers of people, and on an average person’s diet outside of a research setting. And although it provided scientists with information on both recent meals and long-term dietary habits, more research is still needed to refine the technology. But study authors believe the test could become widely available in as little as two years — and if that’s the case, we could be looking at a whole new way of studying the link between our diets and our health.

Scientists Can Tell What You’re Eating by Studying Your Pee