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.
Moyad
Mark A
MA
Department of Urology, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0330, USA. moyad@umich.edu
Combs
Maile A
MA
Vrablic
Angelica S
AS
Velasquez
Janet
J
Turner
Benilda
B
Bernal
Samuel
S
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