Estimation of urinary 24-hr creatinine excretion by body size and dietary protein level: a field survey based on seasonally repeated measurements for residents living in Akita, Japan.
We aimed to investigate the modifying effect of dietary protein level on the estimation of 24-hr creatinine excretion using anthropometric measurements, in a group of 40 healthy Japanese adults, during usual daily life. To evaluate the variability of each measurement during non-restrictive life, we assayed 24-hr urinary excretions of creatinine and urea-N and measured heights and weights once in every three months in a total of 4 times during a year. Urinary urea-N was used as a marker of dietary protein level. Seasonal variability of anthropometrics and urinary excretions was observed on the individual basis. In comparison to the rather small individual variability of weight (mean of CV = 1.2 for males, 1.7 for females), variability of urinary creatinine (CV = 11.7, 8.4) and urea-N (CV = 18.9, 17.3) took larger values. The creatinine excretion was estimated by the following two sets of predictor variables; (I) age, height and weight, (II) age, height, weight and urea-N. Although, a statistically significant estimation was obtained by (I), estimation (II) resulted higher regression coefficient than (I), and contribution of urea-N to the estimation of creatinine was shown. Average level of seasonal variability of each predictor variable was further applied to the regression equation (II). Therefore, the possible difference of 24-hr creatinine excretion caused by the seasonal variability of dietary protein level was estimated to be 9.2% for males and 3.6% for females in the given population. Thus, when one predicting formula of 24-hr creatinine by the use of anthropometrics is applied to other populations, the difference of protein nutritional status should be carefully considered.
Moriyama
M
M
Department of Preventive Medicine and Health Promotion, Nagasaki University School of Medicine.
Saito
H
H
Nakano
A
A
Funaki
S
S
Kojima
S
S
D000328:Adult; D000367:Age Factors; D000886:Anthropometry; D001827:Body Height; D001835:Body Weight; D003404:Creatinine / Q000652:urine*; D004044:Dietary Proteins / Q000378:metabolism*; D005260:Female; D006801:Humans; D007564:Japan; D008297:Male; D008875:Middle Aged; D012621:Seasons
D004044:Dietary Proteins; D003404:Creatinine