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.

Keywords: Ascorbic acid/vitamin C bioavailability; Ester-C®; Leukocytes.

Fig. 1

Study flow diagram. *Washout periods were > 7 days; TP test period (24 h), EC Ester-C^®, AA ascorbic acid, PL placebo

Fig. 2

Flow chart of study subjects. EC Ester-C^®, AA ascorbic acid, PL placebo

Fig. 3

Mean vitamin C concentration and percent changes from baseline in plasma over a 24-h period: a concentration change, Ester-C^® versus placebo; b percent change, Ester-C^® versus placebo; c concentration change, Ester-C^® versus ascorbic acid; d percent change, Ester-C^® versus ascorbic acid. Data are mean ± standard error. Significant differences are indicated: *P < 0.001, Ester-C^® versus placebo; **P = 0.007, Ester-C^® versus placebo; ^†P < 0.001, within-group change from baseline for both Ester-C^® and ascorbic acid

Fig. 4

C_max, AUC_0–24h, and T_max of plasma vitamin C (correcting for baseline) over a 24-h period: a C_max, Ester-C^® versus placebo; b C_max, Ester-C^® versus ascorbic acid; c AUC_0–24h, Ester-C^® versus placebo; d AUC_0–24h, Ester-C^® versus ascorbic acid; e T_max, Ester-C^® versus placebo; f T_max, Ester-C^® versus ascorbic acid. Data are mean ± standard error. Significant differences are indicated: *P < 0.001, Ester-C^® versus placebo; **P = 0.039, Ester-C^® versus ascorbic acid

Fig. 5

Mean vitamin C concentration and percent changes in leukocytes over a 24-h period: a concentration change, Ester-C^® versus placebo; b concentration change, Ester-C^® versus ascorbic acid; c percent change, Ester-C^® versus placebo; d percent change, Ester-C^® versus ascorbic acid. Data are mean ± standard error. Significant differences are indicated: *P < 0.05, Ester-C^® versus placebo percent change (P = 0.042 at 8 h, P = 0.036 at 24 h); **P < 0.05, Ester-C^® versus ascorbic acid percent change (P = 0.028 at 8 h, P = 0.034 at 24 h); ^†P < 0.05, Ester-C^® within-group differences (concentration change P = 0.036 at 24 h; percent change P = 0.040, P = 0.013, and P = 0.001 at 4, 8, and 24 h, respectively)