The Use of Nitrogen to Creatinine Ratios in Random Urine Specimens to Estimate Dietary Protein

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Abstract
In this study, we have considered the use of nitrogen/creatinine ratios (grams of nitrogen per gram of creatinine) in random urine samples to estimate dietary protein. With diets varying from 80 to 125 grams of protein, we compared the accuracy of 3-, 4-, and 5-hour timed urinary nitrogen excretion with nitrogen/creatinine ratios determined from the same samples in the prediction of nitrogen intake. Although 24-hour urinary nitrogen gave the best correlation, we found little difference in results when comparing 4-hour urinary nitrogen with the ratios. Difficulties from diurnal variation of nitrogen excretion were reduced by the use of ratios, but the variability in creatinine excretion among individuals raised other problems. It is concluded that for surveys of large groups of individuals the use of nitrogen/creatinine ratios in random urine samples to estimate protein intake merits further consideration.