Medieval physicians believed that they could diagnose disease by holding up a flask of the patient’s urine to the light and squinting at it. According to scientists at Imperial College London, they could have been on to something.

A team there has completed the first worldwide study of the metabolites (breakdown products) that are found in urine, reflecting the diet, inheritance and the lifestyle of the people from whom it came. They call such studies “metabolomics” by analogy with genomics, which looks at all the genes that make up the human species, and proteomics, which does the same for proteins.

The study used nuclear magnetic resonance spectroscopy to compare racial and national groups by the composition of their urine. From Japan, Beijing, Corpus Christi, Belfast and West Bromwich, urine differs in subtle ways that could provide a powerful new way of linking diet and health.The metabolites they found come from microbes in the gut, from diet and from the metabolism of the host.

The team believes that the research may provide the basis for a “metabolome-wide association” approach to help to understand interactions between lifestyles, environment and genes and how they determine diseases.

The metabolic fingerprints show that people in the US and Britain who share a tendency to high blood pressure and heart problems have similar patterns. Writing in the science journal Nature, the team identifies metabolites linked to high blood pressure, such as the amino acid alanine.

Hippurate, another by-product of gut bacteria, is found in people with lower blood pressure who drink less and eat more fibre in their diet.

Scientists from Imperial College, the US, Belgium, Japan and China took samples from 4,630 volunteers aged between 40 and 59. Professor Jeremy Nicholson, from Imperial College, said: “Metabolic profiling can tell us how specific aspects of a person’s diet and how much they drink are contributing to their risks for certain diseases, and these are things which we can’t investigate by looking at a person’s DNA. What is really important is that we can test out our new hypotheses directly, in a way that is not easy with genetic biomarkers.”

Testing the waters

— Studying the colour, smell and even the taste of urine was once the primary means of diagnosis for physicians

— During the Middle Ages, when anatomy studies were rare and very few postmortem examinations were done, urine was one of the few diagnostic tools available

— One textbook listed 20 possible colours

— Belief in urine analysis began in the late classical era, around AD500, and lasted unchallenged into the Renaissance, when doctors were at last permitted to dissect bodies

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