Hydroxyproline excretion and nutritional status of children

Hydroxyproline excretion was measured in 15 healthy girls, 7 to 9 years of age who participated in a metabolic study for 36 days. During the last 30 days of the study, the diets supplied either 24 or 46 g protein daily. Hydroxyproline excretion by the girls receiving the lower protein intakes decreased from 75.3 ± 18.1 to 57.9 ± 19.2 mg/24 hr. Hydroxyproline excretion of the subjects fed 46 g protein daily remained essentially constant throughout the study. In a second experiment, two replicate metabolic studies, each with 16 girls, 7 to 9 years old, were conducted for 20 days. The basal diet daily supplied 25 g protein and 0.26 g calcium. During days 9 to 20, one-half the subjects were given supplements of lysine, threonine, and methionine and one-half were given an isonitrogenous amount of ammonium citrate. One-half of each group was given daily 1.01 g supplemental calcium as calcium lactate. Hydroxyproline excretion decreased in all groups. The average decrease in excretion was greater in the groups receiving the calcium supplements; however, the difference between the four groups was not statistically significant.