URINARY HYDROXYPROLINE EXCRETION AND VITAMIN-C STATUS IN HEALTHY-YOUNG MEN

The relationship between ascorbic acid status and the urinary excretion of hydroxyproline was examined in 11 healthy male subjects fed an ascorbic acid-deficient diet for 14 wk while in a metabolic unit. The diet provided 5 mg ascorbic acid/d and was supplemented with ascorbic acid to give intakes of 65 mg/d (2 wk), 5 mg/d (4 wk), 605 mg/d (3 wk), 5 mg/d (4 wk), and an average 375 mg/d (1 wk). The urinary excretion of hydroxyproline increased by an average of 16% and 30% after the first and second depletion periods, respectively, and decreased to baseline values after supplementation with normal or high doses of vitamin C. Significant (p < 0.05) inverse correlations were found between urinary hydroxyproline and plasma, red cell, and leukocyte ascorbic acid. These results showed that urinary hydroxyproline excretion increases during human vitamin C deficiency but that this effect is not strong enough to provide a reliable marker of mild vitamin C deficiency.