Urinary fructose: a potential biomarker for dietary fructose intake in children

Recently, urinary fructose and sucrose excretion in 24-h urine have been established experimentally as new biomarkers for dietary sugar intake in adults. Our objective was to investigate 1) whether the fructose biomarker is also applicable in free-living children and 2) for what kind of sugar it is standing for.

Intakes of added and total sugar (including additional sugar from fruit and fruit juices) were assessed by 3-day weighed dietary records in 114 healthy prepubertal children; corresponding 24-h urinary fructose excretion was measured photometrically. The associations between dietary sugar intakes and urinary fructose excretion were examined using linear regression models. To determine whether one of the two sugar variables may be better associated with the urinary biomarker, the statistical Pitman's test was used.

Added and total sugar correlated significantly with urinary fructose, but the linear regression indicated a weak association between intake of added sugar and urinary log-fructose excretion (β=0.0026, R(2)=0.055, P=0.01). The association between total sugar intake and log-urinary fructose (β=0.0040, R(2)=0.181, P<0.001) showed a significantly better fit (P<0.05).

Urinary fructose excretion seems to be rather applicable for the estimation of total sugar intake than for the estimation of added dietary sugar intake in children. However, as excreted fructose stems almost exclusively from the diet (both from food-intrinsic and added intakes), it can be assumed that urinary fructose represents a potential biomarker for total dietary fructose intake, irrespective of its source.