Peed piper: Urine fine to define dietary kind
A team from Imperial College London, Newcastle University and Aberystwyth University created urinary metabolite models for each of four different dietary interventions, testing urine samples from participants, and comparing them against control groups.
Nineteen healthy volunteers aged between 21 and 65 and with BMIs (Body Mass Index) of 20-35 each had four in-patient stays of 72 hours, during which time they were given one of the four diets, with each diet randomly assigned. Diets ranged from one very close to UK guidelines (diet 1), including fish, lean meats and fruits and vegetables, to a high-fat, low-fibre diet (diet 4).
Urine was collected throughout the day from each participant, and pooled to give 24-hour samples, which were then analysed using nuclear magnetic resonance imaging (NMR). These were then compared to models developed by the researchers attempting to predict the metabolite content of urine from the different diets.
Markers for fish and veggies detected
The team found their predictions were valid, with biomarkers such as hippurate for fruits and vegetables, dimethylamine and trimethylamine N-oxide (TMAO) for fish, and other markers for cruciferous vegetables and oily fish and chicken, present in much larger quantities in diet 1 than diet 4.
The researchers also tested their findings against urine samples from 66 Danish volunteers who were not provided with specific diets but completed food surveys, and found the results remained valid.
While the tests need refinement, the researchers said their work has potential to improve health screening, in terms of cost, time and accuracy.
“Existing methods for dietary assessment — eg, dietary diaries (which require coding and data entry), food frequency questionnaires, and dietary recalls — are expensive (our own estimated cost is £60 (€69) for the complete analysis, including quality control of a one day dietary recall by an experienced nutritionist or dietitian),” wrote the researchers in a paper in the journal Lancet Diabetes and Endocrinology.
“Translating our study method into clinical practice is a cost-effective and time-effective alternative for objective dietary assessment—the cost is roughly £20 (€23) per sample for robust analysis by NMR, which takes less than five minutes per sample to run (excluding sample preparation),” they added.
“A major weakness in all nutrition and diet studies is that we have no true measure of what people eat. We rely solely on people keeping logs of their daily diets – but studies suggest around 60% of people misreport what they eat to some extent. This test could be the first independent indicator of the quality of a person's diet – and what they are really eating,” said Gary Frost, senior author of the study and a professor at the Department of Medicine at Imperial.
No sausage and chips detection – yet
Isabel Garcia-Perez, co-author from the Faculty of Medicine at Imperial, said: “We need to develop the test further so we can monitor the diet based on a single urine sample, as well as increase the sensitivity. This will eventually provide a tool for personalised dietary monitoring to help maintain a healthy lifestyle.
“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."
They said the test could be available to the public in two years.
Source: Lancet Diabetes and Endocrinology
Published online ahead of print, doi: 10.1016/S2213-8587(16)30419-3
“Objective assessment of dietary patterns by use of metabolic phenotyping: a randomised, controlled, crossover trial”
Authors: Garcia-Perez, I, et al.