The relationship between urinary polyphenol metabolites and dietary polyphenol intakes in young adults

Spot urinary polyphenols have potential as a biomarker of polyphenol-rich food intakes. The aim of this study is to explore the relationship between spot urinary polyphenols and polyphenol intakes from polyphenol-rich food sources. Young adults (18-24 years old) were recruited into a sub-study of an online intervention aimed at improving diet quality. Participants' intake of polyphenols and polyphenol-rich foods was assessed at baseline and 3 months using repeated 24-h recalls. A spot urine sample was collected at each session, with samples analysed for polyphenol metabolites using LC-MS. To assess the strength of the relationship between urinary polyphenols and dietary polyphenols, Spearman correlations were used. Linear mixed models further evaluated the relationship between polyphenol intakes and urinary excretion. Total urinary polyphenols and hippuric acid (HA) demonstrated moderate correlation with total polyphenol intakes (r(s) = 0 center dot 29-0 center dot 47). HA and caffeic acid were moderately correlated with polyphenols from tea/coffee (r(s) = 0 center dot 26-0 center dot 46). Using linear mixed models, increases in intakes of total polyphenols or polyphenols from tea/coffee or oil resulted in a greater excretion of HA, whereas a negative relationship was observed between soya polyphenols and HA, suggesting that participants with higher intakes of soya polyphenols had a lower excretion of HA. Findings suggest that total urinary polyphenols may be a promising biomarker of total polyphenol intakes foods and drinks and that HA may be a biomarker of total polyphenol intakes and polyphenols from tea/coffee. Caffeic acid warrants further investigation as a potential biomarker of polyphenols from tea/coffee.

Automated summary

Spot urinary polyphenols have potential as a biomarker for polyphenol-rich food intake. The study found moderate correlation between urinary polyphenols and polyphenol intakes from different sources, especially with polyphenols from tea/coffee. Findings suggest that total urinary polyphenols may be a promising biomarker for total polyphenol intakes from foods and drinks, with hippuric acid (HA) identified as a potential biomarker for polyphenols from tea/coffee.