Moore LB, et al. - The researchers estimated the validity of urinary sodium, nitrogen, and total sugars (TS) excretion as biomarkers for sodium, protein, and added sugars (AS) intake in nonobese adolescents. For sodium intake, urinary sodium appeared to be a valid biomarker in nonobese adolescents. Urinary nitrogen was correlated with protein intake, but nitrogen excretion rates were less than previously reported for adults, probably owing to adolescent growth rates. At 25% AS intake, TS excretion reflected AS and was responsive to the change in AS intake. Urinary biomarkers, therefore, were promising objective indicators of dietary intake in adolescents. However, to confirm these findings, larger-scale feeding trials were required.

• In a randomly assigned order, 33 adolescents [12-18 y of age, 47 ± 25th percentile (mean ± SD) of body mass index (BMI; in kg/m²) for age] consumed 5% AS [low added sugars (LAS)] and 25% AS [high added sugars (HAS)] isocaloric, macronutrient-matched (55% carbohydrate, 30% fat, and 15% protein) diets for 7 d each with a 4-wk washout period between diets in a crossover controlled feeding study design.
• The researchers collected 24-h urine samples on the final 2 d of each diet period.
• In this study, 32 adolescents completed all measurements (97% retention).

• Finding revealed that urinary sodium was not different from the expected 90% recovery (mean ± SD: 88% ± 18%, P = 0.50).
• Although it was below the 80% expected recovery (62% ± 7%, P < 0.001), urinary nitrogen was correlated with protein intake (r = 0.69, P < 0.001).
• During the HAS diet, urinary TS values were correlated with AS intake (r = 0.77, P < 0.001) and had a higher R² value of 0.28 than did AS intake (R² = 0.36).
• Between LAS (0.226 ± 0.09 mg/d) and HAS (0.365 ± 0.16 mg/d) feeding periods (P < 0.001), TS excretion differed.