Exploring Triple-isotopic Signatures of Water in Human Exhaled Breath, Gastric Fluid and Drinking Water Using Integrated Cavity Output Spectroscopy.

Water, the major body fluid in humans, has four main naturally occurring isotopologues, H2(16)O, H2(17)O, H2(18)O and H(2)H16O (i.e. HD16O) with different masses. The underlying mechanisms of the isotope-specific water-metabolism in human gastrointestinal (GI) tract and respiratory system are largely unknown and remained illusive for several decades. Here, a new strategy has been demonstrated that provides the direct quantitative experimental evidences of quadruple-isotopic signatures of water-metabolism in human body in response to the individual's water intake habit. The distribution of water isotopes have been monitored in drinking water (DW) (deltaD =-36.59+/-10.64 per thousand (SD), delta18O= -5.41+/-1.47 per thousand (SD) and delta17O= -2.92+/-0.79 per thousand (SD)), GI fluid (GF) (deltaD =-35.91+/-7.30 per thousand (SD), delta18O= -3.98+/-1.29 per thousand (SD) and delta17O= -2.37+/-0.57 per thousand (SD)) and human exhaled breath (EB) (deltaD =-119.63+/-7.27 per thousand (SD), delta18O= -13.69+/-1.23 per thousand (SD) and delta17O= -8.77+/-0.98 per thousand (SD)) using the laser-based off-axis integrated cavity output spectroscopy (OA-ICOS) technique. This study explored a new analytical method to disentangle the competing effects of isotopic fractionations of water during respiration in humans. In addition, our findings revealed that deuterium-enriched exhaled semi-heavy water, i.e. HD(16)O is a new marker of the non-invasive assessment of the ulcer-causing H. pylori gastric pathogen. We also clearly showed that the water-metabolism-derived quadruple-isotopic compositions due to impaired water absorption in GI tract can be used as unique tracers to track the onset of various GI dysfunctions. These findings are thus bringing a new analytical methodology for better understanding the isotope-selective water-metabolism that will have enormous applications in clinical testing purpose.