What your pee reveals about your diet
4 March 2021
The coronavirus pandemic has turned attention on the risks of an unhealthy lifestyle and being overweight. But with so much conflicting dietary advice, how do you know what’s going to work for you? Dr Joram Posma believes the answer may be in your pee.
Research has shown that obesity increases the chances of falling seriously ill or being hospitalised with COVID-19. Prime Minister Boris Johnson’s own brush with coronavirus prompting the unveiling of a new obesity strategy, urging the nation to shed the pounds to beat COVID-19 and protect the NHS.
But as anyone who has ever tried to lose weight knows only too well, this isn’t as easy as it sounds. There’s a lot of conflicting advice about the right diet to follow, so how do you know which is the right approach for you? According to Health Data Research UK Rutherford fellow Dr Joram Posma at Imperial College London, a good place to start is by knowing what you’re eating in the first place.
What goes in must come out
When you eat, your body breaks down the compounds in your food into molecules called metabolites, which are filtered out by your kidneys and end up in your urine. Different foods result in different molecules in your pee, so identifying these compounds can give you an accurate fingerprint of what you have eaten, and whether the foods you have chosen are helping you gain or lose weight.
“We looked at the compounds in the urine of nearly 2,000 people using a technique called NMR spectroscopy, then compared the results of their urine test with what they said they ate,” says Joram.
The study, which was published in Nature Food in June, identified 46 compounds that could be linked to consuming specific foods and nutrients including citrus fruits, fructose, glucose, vitamin C, red meats, white meats, salty foods, and foods rich in calcium.
“Often, when you visit a dietician for help with losing weight, the first thing they will ask is ‘what do you usually eat?’. But remembering what you have eaten is notoriously tricky and often inaccurate,” says Joram.
“Measuring the compounds in urine is a much more accurate way of capturing what people eat because people often forget, over- or under-report certain foods.”
Trialling the test
This simple urine test, which only takes 5 minutes, could help give people a better snapshot of what they are eating and help them identify changes that are likely to improve their diet. It’s an idea that Joram and his team put to the test in a second study involving some adventurous volunteers.
“We did a clinical trial where 19 volunteers stayed with us at a clinic for a week, so we knew exactly what they were eating. They stayed four times and followed four different diets, ranging from unhealthy to very healthy. Using the results from their urine tests, we came up with an algorithm that tells us how healthily someone is eating based on a profile of the compounds in their urine sample,” says Joram, who published the results of this study in a second paper in Nature Food.
You do you
Although people’s digestive systems tend to make the same metabolites when they eat the same foods, they can vary in concentration, because we all process food differently. This can explain why specific diets can work for one person but not for another. So the results of a urine profile can help provide people with personalised diet advice, and also reveal whether they are sticking to it.
“We saw that the ‘healthier’ a person’s diet, the more energy they lost in their urine, which is good if you are trying to lose weight. We also noticed that people who respond well to a particular diet tend to lose a lot of energy in their urine when they are on that diet,” says Joram.
“We can also see whether people are following their dieticians advice or not and whether that advice is working for them,” he adds.
The urine test is currently being trialled within the NHS, aiming to help doctors and dieticians manage patients who are overweight and at risk from conditions like diabetes and cardiovascular disease.
Meanwhile, Joram and the team are continuing to study what the metabolites in our urine can tell us about our health. They are verifying their results using datasets they have found through the Health Data Research Innovation Gateway, and are investigating whether urine profiles can predict blood pressure or cardiovascular risk.
“You may not think about it when you flush the toilet, but there’s a lot of information about your health in your urine – we just need to work out how to read it!” he says.
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