Abstract
Thirty four young female subjects living in the metabolic unit in the college were fed the experimental diets, 24-hour urine throughout the experimental periods were collected and urinary creatinine and creatine contents were analyzed. Three subjects were fed the diet with 200 g meat for five days after five day period of meat free diet. Creatinine excretion increased on the first day of the meat diet and maintained constant level following four days. Creatine excretion increased successively throughout the meat diet. Other five subjects were fed protein free diet for ten days and the following ten days the diet including 250g egg were fed. Creatinine excretion decreased slowly throughout the protein free diet and the egg diet periods. Creatine excretion decreased immediately into very low level in the protein free diet period but slightly increased by the egg diet. Other three subjects were fed meat free diet (protein 80g) for three days after the ten days period of protein free diet, but both creatinine and creatine excretion did not increase at all compared with the prior period. Another group of subjects were fed meat free and 100g, 200g, 300g of meat containing diet for three or four days each. Their creatinine excretion increased as increasing meat intake, but no significant difference was observed between the urinary creatinine level with meat free diet and meat 100 g diet.
These results suggest that when lean body mass is estimated by urinary creatinine content in the field work, it is necessary to collect the urine for three to five days in which period creatine rich foodstuffs-meat, fish or poultry intake are restricted less than 100g. Furthermore another equation to calculate lean body mass by urinary creatinine for Japanese people should be deviced in the future, because the equations suggested up to the present are calculated from the subjects whose diet contained meat or protein far higher level than usual Japanese diet.
