Vitamin C metabolites, independent of smoking status, significantly enhance leukocyte, but not plasma ascorbate concentrations.
BACKGROUND
The objective of this study was to test the effects of acute doses of vitamin C alone, calcium ascorbate with vitamin C metabolites, and placebo, on total plasma and leukocyte vitamin C concentrations over 24 hours.


METHODS
A double-blind, placebo-controlled, four-way crossover study was performed consisting of four separate phases lasting 24 hours each and utilizing one of four oral 1000-mg preparations within each phase (one of vitamin C alone, two separate vitamin C formulations of calcium ascorbate with vitamin C metabolites, and placebo). There was a 7-day washout between phases, and blood draws at seven time points within each phase of the study for a total of 28 serologic measurements per subject and 420 total measurements for the entire clinical trial. Vitamin C concentration in plasma and leukocytes were measured by high-performance liquid chromatography at baseline and at six sequential time periods over 24 hours.


RESULTS
Fifteen healthy males were enrolled, aged 18-39 years; nine were had never smoked and six were chronic smokers. No significant difference in plasma vitamin C levels was observed when comparing the different preparations. However, at 24 hours, calcium ascorbate with metabolites resulted in significantly higher concentrations of vitamin C in leukocytes (P<0.0001) compared with vitamin C alone. These results were similar for both metabolite formulations, and independent of smoking status.


CONCLUSIONS
Regardless of smoking status, vitamin C metabolites may enhance leukocyte utilization of vitamin C itself, despite no consistent difference in plasma levels among the different preparations. A larger clinical investigation is warranted to confirm these preliminary findings, and to determine the clinical relevance of this impact on overall immune function.
Department of Urology, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0330, USA. moyad@umich.edu
Mark A
MA
Moyad
Maile A
MA
Combs
Angelica S
AS
Vrablic
Janet
J
Velasquez
Benilda
B
Turner
Samuel
S
Bernal
D000293:Adolescent; D000328:Adult; D001205:Ascorbic Acid / Q000097:blood / Q000493:pharmacokinetics*; D001224:Aspartic Acid / Q000097:blood; D002851:Chromatography, High Pressure Liquid; D018592:Cross-Over Studies; D004311:Double-Blind Method; D006801:Humans; D007962:Leukocytes / Q000378:metabolism*; D008297:Male; D012907:Smoking / Q000378:metabolism*; D014815:Vitamins / Q000493:pharmacokinetics*; D055815:Young Adult
D014815:Vitamins; D001224:Aspartic Acid; D001205:Ascorbic Acid