Serum and Urine Metabolites in Healthy Men after Consumption of Acidified Milk and Yogurt

Abstract

The identification of molecular biomarkers that can be used to quantitatively link dietary intake to phenotypic traits in humans is a key theme in modern nutritional research. Although dairy products (with and without fermentation) represent a major food group, the identification of markers of their intake lags behind that of other food groups. Here, we report the results from an analysis of the metabolites in postprandial serum and urine samples from a randomized crossover study with 14 healthy men who ingested acidified milk, yogurt, and a non-dairy meal. Our study confirms the potential of lactose and its metabolites as markers of lactose-containing dairy foods and the dependence of their combined profiles on the fermentation status of the consumed products. Furthermore, indole-3-lactic acid and 3-phenyllactic acid are two products of fermentation whose postprandial behaviour strongly discriminates yogurt from milk intake. Our study also provides evidence of the ability of milk fermentation to increase the acute delivery of free amino acids to humans. Notably, 3,5-dimethyloctan-2-one also proves to be a specific marker for milk and yogurt consumption, as well as for cheese consumption (previously published data). These molecules deserve future characterisation in human interventional and observational studies.

Age-Dependent Serum Volatilomics of Milk and Yogurt Intake: A Randomized Crossover Study in Healthy Young and Older Men

“… 48 It is important to note that the postprandial increase in p -cresol we observed is not specific to the intake of dairy products, as we recently shown that this molecule also increases significantly after the intake of a non-dairy high-fat meal. 49 Furthermore, cresol and phenol are products of the colonic fermentation of dietary proteins that are not produced by the human organism and can be indicative of a protein overload of the small intestine digestive capacity. 50 …”

“…48 It is important to note that the postprandial increase in p-cresol we observed is not specific to the intake of dairy products, as we recently shown that this molecule also increases significantly after the intake of a non-dairy high-fat meal. 49 Furthermore, cresol and phenol are products of the colonic fermentation of dietary proteins that are not produced by the human organism and can be indicative of a protein overload of the small intestine digestive capacity. 50 The significantly higher postprandial increase in p-cresol and phenol in the OA population after an identical dairy challenge as the YA is remarkable and may be suggestive of a reduced capacity to digest and assimilate dietary proteins in the small intestine and/or of a difference in the composition of the gut microbiota.…”