title: Determination of plasma and leukocyte vitamin C concentrations in a randomized, double-blind, placebo-controlled trial with Ester-C(®).
abstract: BACKGROUND
  Rapid uptake of vitamin C into blood and retention in tissues are important indicators of the efficacy of vitamin C supplementation and its immune-supporting role. The objective of this study was to evaluate the bioavailability of vitamin C in plasma (reflective of recent intake) and leukocytes (reflective of tissue stores and influences on immune function) from a novel vitamin C formulation, Ester-C(®).
  
  
  METHODS
  The study was a double-blind, placebo-controlled, crossover trial. Thirty-six subjects, 18-60 years of age, were randomized to receive placebo (PL, 0 mg vitamin C), ascorbic acid (AA, 1000 mg vitamin C), and Ester-C(®) (EC, 1000 mg vitamin C). Plasma and leukocyte vitamin C were measured baseline and at 2, 4, 8 and 24 h postdose.
  
  
  RESULTS
  The concentration and percent change from baseline in plasma were significantly higher with EC at all time points when compared to PL. No significant differences between EC and AA were observed in plasma concentration. Maximum plasma concentration was higher for EC compared to AA (P = 0.039) and PL (P < 0.001). Plasma area under the curve (AUC0-24h) was higher for EC (P < 0.001) compared to PL. The concentration change from baseline in leukocyte vitamin C was increased with EC at 24 h post-dose (P = 0.036) while no significant within-group changes were observed in AA or PL at any time point. The percent change in leukocyte vitamin C concentration was higher for EC at 8 and 24 h compared to AA (P = 0.028 and P = 0.034, respectively) and PL (P = 0.042 and P = 0.036, respectively).
  
  
  CONCLUSIONS
  A single dose of EC resulted in favorable percent change in leukocyte vitamin C concentration compared to AA and PL, indicating EC is retained longer within leukocytes. Trial registration ClinicalTrials.gov Identifier NCT01852903.
authors: Department of Nutrition & Scientific Affairs, NBTY, Inc., Ronkonkoma, NY 11779 USA.
authors: Susan H
authors: SH
authors: Mitmesser
authors: Department of Nutrition & Scientific Affairs, NBTY, Inc., Ronkonkoma, NY 11779 USA.
authors: Qian
authors: Q
authors: Ye
authors: KGK Synergize, Suite 1440, One London Place 255 Queens Avenue, London, ON N6A 5R8 Canada.
authors: Mal
authors: M
authors: Evans
authors: Department of Nutrition & Scientific Affairs, NBTY, Inc., Ronkonkoma, NY 11779 USA.
authors: Maile
authors: M
authors: Combs
keywords: Ascorbic acid/vitamin C bioavailability; Ester-C®; Leukocytes