Effect of age and sex on the urinary elimination of a single dose of mixed flavonoids: results from a single-arm intervention in healthy United Kingdom adults.

Background: Nutrition intervention trials demonstrate that increased flavonoid intake can have clinically meaningful impacts on disease outcomes/biomarkers; however, high variability in absorption and metabolism and large heterogeneity in biochemical and physiological responses are observed. The etiology of this variability is poorly understood.

Objective: The objective of this study was to explore the relationships between sex, age, and microbiota speciation on mixed flavonoid elimination over 24 h.

Methods: Healthy males and females (n = 163) prospectively recruited on the basis of age (18-30 y or 65-77 y) and sex consumed a standardized flavonoid-rich test meal providing 640-mg cocoa/chocolate flavan-3-ols, 340-mg citrus flavanones, and 390-mg blackberry anthocyanins. Urinary samples collected at baseline (-24 to 0 h), 0 to 3.5 h, >3.5 h to 7 h, and >7 to 24 h were analyzed for flavonoids and their metabolites by ultra-high-performance liquid chromatography-mass spectrometry (UPLC-MS/MS). Stool microbiome speciation was determined via Illumina sequencing. Linear mixed-effect models were used to assess differences in cumulative excretion across age and sex with time-by-group interaction taken as the principal analysis of effect.

Results: There were no group (older females, older males, younger females, and younger males) differences in total 24 h urinary metabolite recovery, but there was a trend toward a higher rate of cumulative recovery in older males versus younger males at 24 h (P-group at 24h = 0.06). Of 76 metabolites, 20 had significantly different times of maximum urine excretion (Tmax) by age and 9 by sex, with a later mean Tmax observed for older participants (92% of instances). Associations with age were not mediated by body mass index (BMI) or microbiome speciation. Significant differences in maximum urine excretion (Cmax) by sex were observed for only 6 metabolites and differences by age for 5 metabolites.

Conclusion: Total elimination recovery of (poly)phenols was relatively consistent across age and sex groups, whereas elimination kinetics (Tmax) differed substantially being much later in older indivudals, possibly resulting from differences in intestinal transit time or kidney clearance. Assuming (poly)phenol metabolites have varying biological activities, establishing dose-response relationships and defining metabolite profiles in population subgroups is required to inform the future development of dietary flavonoid/(poly)phenol recommendations. This trial was registered at clinicaltrials.gov as NCT01922869.