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Monday, May 6, 2013

You are what you breathe


What does your breath say about you? For one thing, it may one day be used to identify you. Or, more likely, it could be used as a way to assess your health. In a recent PLOS One paper, researchers from the University of Zurich and ETH Zurich show that eleven different test subjects each had unique breath signatures.

The subjects were asked to provide four breath samples per day for nine days. The participants went about their normal mouth-using activities except for thirty minutes prior to each sampling, during which they refrained from eating, drinking or brushing their teeth. None of the subjects were smokers.

At testing times, the participants breathed into a mass spectrometer that analyzed the volatile components in their breath. Take a look at the figure below. The larger image is a 3D plot of the various compounds that were detected in people’s breath. Each color and shape displays all the samples taken from that particular person.

Figure 3 Projection of the 193 breath mass spectra onto the first three dimensions obtained by supervised Kruskal-Wallis/PCA/CA.

PLoS ONE, 8 (4) DOI: 10.1371/journal.pone.0059909.

You can see two interesting things here. One, each person’s breath is distinct (though the breath of some of the subjects had fairly similar properties). Two, and perhaps even more intriguingly, nobody’s breath changed all that much over the course of the nine-day study. Unless people were eating and drinking the same things day after day, this means that what we ingest has a lot less to do with our breath than I would have thought.

The inset shows the predictive power of the spectrophotometric analysis, that is, whether the researchers could identify the subjects from their breath patterns. For example, in the top row you can see how often test subject one was matched to breath from any of the eleven participants. In that case, the correct match occurred about 80% of the time, which was more or less the average.

Of course, we’re a long way from using ‘breathprint’ analysis for either security or health screenings. Eleven people are hardly enough to confirm the idea that we all have identifiable breath signatures. As far as health goes, we don’t even know what all the compounds in breath are, let alone which ones to watch out for. Still, it’s certainly interesting to know that we may each have a stable mix of breath volatiles regardless of what we eat. That may be better news for some than for others.



Martinez-Lozano Sinues, P., Kohler, M., & Zenobi, R. (2013). Human Breath Analysis May Support the Existence of Individual Metabolic Phenotypes PLoS ONE, 8 (4) DOI: 10.1371/journal.pone.0059909.