Identification of urinary food intake biomarkers for milk, cheese and soy-based drink by untargeted GC-MS and NMR in healthy humans

The measurement of food intake biomarkers (FIBs) in biofluids represents an objective tool for dietary assessment. FIBs of milk and cheese still need more investigation due to the absence of candidate markers. Thus, an acute intervention study has been performed to sensitively and specifically identify candidate FIBs. Eleven healthy male and female volunteers participated in the randomised, controlled crossover study that tested a single intake of milk and cheese as test products, and soy based drink as a control. Urine samples were collected at baseline and up to 24h at distinct time intervals (0-1, 1-2, 2-4, 4-6, 6-12 and 12-24h) and were analysed using an untargeted multi-platform approach (GC-MS and 1H-NMR). Lactose, galactose and galactonate were identified exclusively after milk intake while for other metabolites (allantoin, hippurate, galactitol and galactono-1,5-lactone) a significant increase has been observed. Urinary 3-phenyllactic acid was the only compound specifically reflecting cheese intake although alanine, proline and pyroglutamic acid were found at significantly higher levels after cheese consumption. In addition, several novel candidate markers for soy drink were identified such as pinitol and trigonelline. Together, these candidate FIBs of dairy intake could serve as a basis for future validation studies under free-living conditions.