Diet and other factors affecting the variability of breath composition

Background Exhaled breath contains information concerning exposure to xenobiotics, food and beverage consumption, normal and abnormal physiology and presence of bacteria. Such richness of information results in a large intra- and inter-individual variability of breath composition, which is further increased by sampling conditions, circadian rhythms and diet. Variability hinders the identification of specific biomarkers or “breathprints” and makes it complex to tell pathological from healthy subjects apart. Methods Breath composition was analysed in 20 healthy subjects following an omnivorous (n= 10) or a vegan (n= 10) diet under different conditions. Mixed breath was sampled by asking each subject to fill a Nalophan bag, then 100 mL of sample were loaded into a sorbent tube (250 mg of Tenax GR ,70/80 mesh) before being analysed by thermal desorption coupled to gas chromatography / mass spectrometry. Results Respiratory rate and ventilation modified breath composition, where the largest variations were observed with isoprene and acetone. Vegans showed lower values of VOCs related to oxidative stress compared to omnivorous subjects, but differences were not very large. Individual behaviours concerning smoke or consumption of specific foods were also mirrored in breath. Conclusions Even if some information is available in literature, more and more experiments are showing that variability of breath composition in nominally healthy subjects is larger than previously expected. The breath community should put more emphasis in understanding the role and the relative importance of the sources of such variability as part of the work in standardizing breath measurements.