Daily Determination of Plasma, Serum and White Cell-Platelet Ascorbic Acid in Relationship to the Excretion of Ascorbic and Homogentisic Acids by Adults Maintained on a Controlled Diet

and Conclusions Report is made of a study in which healthy adult women were maintained for 52 days on a controlled diet with a controlled intake of ascorbic acid. Daily measurements were made of total ascorbic acid in serum, plasma and white blood cells plus platelets, of reduced ascorbic acid in serum and plasma, of urinary ascorbic acid and of urinary homogentisic acid equivalents. Total ascorbic acid was measured in whole blood for the last 7 days. Data from this study show that: 1. The concentrations of both total and reduced ascorbic acid were significantly higher in serum than in plasma. 2. The concentration of total ascorbic acid was significantly higher than the concentration of reduced ascorbic acid in both serum and plasma. 3. A daily intake of 25 mg of ascorbic acid was not sufficient to maintain the ascorbic acid of the blood at a “good” level in 4 subjects. 4. A daily intake of 75 mg of ascorbic acid was sufficient to maintain the ascorbic acid of the blood at a “good” level in one subject. 5. There is no evidence, on the basis of homogentisic acid excretion, that a daily intake of 25 mg of ascorbic acid is not sufficient to maintain normal metabolism of tyrosine and phenylalanine. 6. White cell-platelet ascorbic acid levels fell to half or less of initial values in 4 subjects ingesting 25 mg of ascorbic acid daily.