Preventing the common cold with a vitamin C supplement: A double-blind, placebo-controlled survey

A recent UK trial found a reduction in recurrent colds in a nine-week trial in both sexes (RR 0.13; 95% CI 0.03 to 0.53).

“Nevertheless, a recent UK trial found a reduction in recurrent colds in a nine‐week trial in both sexes (RR 0.13; 95% CI 0.03 to 0.53) (Van Straten 2002) (seeHemilä 2006a).”

Another study captured the incidence and symptoms of the common cold.

“One study investigated the effect of Calcium ascorbate EC on immune function by assessing neutrophil functionality (phagocytosis) and the number of different lymphocyte subsets and natural killer cells after ex vivo stimulation [30], while another captured the incidence and symptoms of the common cold [28].”

Van Straten and Josling found a shorter duration of severe symptoms compared to placebo (average 1.8 vs 3.1 days, p < 0.03).

“Those in the Calcium ascorbate EC group had significantly fewer common cold episodes (37 in comparison with 50 in the placebo group, p < 0.05) and a shorter duration of severe symptoms compared to the placebo group (average of 1.8 vs. 3.1 days in the placebo group, p < 0.03).”

The lower infection risk reported with Calcium ascorbate EC is consistent with reported improvements in immune cell function and in leucocyte vitamin C reported in other studies.

“The lower infection risk reported with Calcium ascorbate EC in [28] is consistent with the reported improvements in immune cell function [30] and in leucocyte vitamin C reported in other studies [16,27].”

Van Straten and Josling found those in the Calcium ascorbate EC group had significantly fewer common cold episodes (37 vs 50 in placebo, p < 0.05).

“Those in the Calcium ascorbate EC group had significantly fewer common cold episodes (37 in comparison with 50 in the placebo group, p < 0.05) and a shorter duration of severe symptoms compared to the placebo group (average of 1.8 vs. 3.1 days in the placebo group, p < 0.03).”

In that study, indigestion occurred most frequently in the placebo group (10%) compared to 4% among those receiving 1000 mg Calcium ascorbate EC daily over 60 days, while heartburn incidence was 4% and 7%, respectively.

“Indigestion occurred most frequently in the placebo group, at 10%, compared to 4% among those receiving 1000 mg Calcium ascorbate EC daily over a 60-day period, while the incidence of heartburn was 4% and 7%, respectively.”

From the NICE checklist quality assessment of thirteen RCTs, ten (77%) showed low risk of bias, two (15%) high risk, and one (8%) unclear risk.

“From the assessment of the methodological quality of thirteen RCTs, ten (77%) showed a low risk of bias [12,16,27,28,29,30,31,32,35,37,38], two (15%) showed a high risk of bias [33,36] and one (8%) showed an unclear risk of bias [34].”

Van Straten and Josling found an overall low incidence of side effects among 168 participants.

“Van Straten and Josling [28] found an overall low incidence of side effects among the 168 participants in their study.”

Studies using Calcium ascorbate EC reported favorable effects on leukocyte vitamin C concentration, showed improved immunity based on cell functions and numbers, and reported fewer colds and a shorter duration of severe cold symptoms compared to placebo.

“Studies using Calcium ascorbate EC reported favorable effects on leukocyte vitamin C concentration [16,27], showed improved immunity (based on cell functions and numbers) [30], and reported fewer colds and a shorter duration of severe cold symptoms compared to placebo [28].”