Efficacy of urine urea nitrogen measurement to assess the compliance with protein restricted diets

espanolIntroduccion: la restriccion proteica es fundamental en el manejo de la enfermedad renal cronica. Objetivo: evaluamos la utilidad de la medicion de nitrogeno ureico urinario como marcador de restriccion proteica. Metodos: participantes jovenes sanos fueron divididos aleatoriamente en dos grupos. Un grupo recibio una dieta con 30 kcal/dia/kg peso corporal y 1 g/proteina/dia/kg peso corporal y el otro recibio una dieta con la misma cantidad de calorias pero con 0,6 g/kg peso corporal de proteina. Al inicio, a los siete y a los 14 dias, los participantes respondieron una encuesta dietaria de recordatorio de 24 horas. Ademas, recolectaron orina de 24 horas y se les tomo una muestra aislada de orina al comienzo y a los 14 dias de la intervencion para medir creatinina y nitrogeno ureico. Resultados: cuarenta y un participantes de 29 ± 5 anos completaron el estudio. El grupo que consumio 0,6 g/kg de proteinas redujo su ingesta proteica de 0,88 ± 0,06 a 0,59 ± 0,05 g/kg/dia durante la intervencion. En este grupo se observo una reduccion significativa en la excrecion urinaria de nitrogeno ureico en 24 horas. No se observo tal reduccion en el grupo que consumio 1 g/kg de proteinas. La tasa de probabilidad de detectar una reduccion en la ingesta proteica en las encuestas dietarias, cuando se observaba una disminucion en la excrecion urinaria de nitrogeno ureico/mg creatinina de 24 horas, fue de 5,75 (intervalos de confianza de 95% = 1,29-25,55, p = 0,02). No hubo cambios significativos en la excrecion de nitrogeno ureico en las muestras aisladas de orina. Conclusion: las mediciones repetidas de nitrogeno ureico urinario en 24 horas son un marcador de restriccion dietaria de proteinas. EnglishBackground: protein restriction is the mainstay of dietary management of chronic kidney disease. Aim: to assess the usefulness of urine urea nitrogen measurement as a marker of protein restriction. Methods: healthy young participants were randomly divided in two groups. During 14 days, one group received a diet containing 30 kcal/kg body weight and 1 g protein/kg body weight and the other group received a diet with the same amount of calories and 0.6 g/kg of proteins. At baseline, seven days and 14 days, 24 h dietary recalls were answered by the participants. They collected 24 hour urine and provided spot urine samples at baseline and at the end of the intervention, to measure creatinine and urea nitrogen. Results: forty-one participants aged 29 ± 5 years completed the follow-up. According to 24h dietary recalls, the group receiving 0.6 g/kg protein reduced significantly the protein intake during the intervention from 0.88 ± 0.06 to 0.59 ± 0.05 g/kg/day. A significant reduction in 24 h urea nitrogen excretion was also observed in this group. In the group receiving 1 g/kg of protein, no significant changes in 24 h urea nitrogen excretion were observed. Among all participants, the odds ratio of observing a reduction in protein intake in the dietary survey was 5.75 (95% confidence intervals 1.29-25.55, p = 0.02), when a reduction in 24 h urea nitrogen excretion corrected by creatinine was observed. No changes were observed in urea nitrogen excretion in spot urine samples. Conclusions: repeated urea nitrogen excretion measured in 24 h urine samples can be a reliable indicator of dietary protein restriction.