Purpose: Viral upper respiratory infections are associated with significant health and economic impact. This study sought to determine the efficacy of routine immune system micronutrient supplementation on the incidence, duration and severity of common cold symptoms.
Methods: This pilot study was a randomized, double-blinded, placebo-controlled trial of N = 259 with asymptomatic participants aged 18 to 65 in two cold seasons of 2016 and 2017. The treatment group received an immune system targeted micronutrient caplet, while the placebo group received a micronized cellulose caplet externally identical to the treatment caplet. Weekly surveys were sent electronically to participants to document common cold incidence, duration and severity. Primary statistical results were obtained using mixed-effects logistic regressions to account for longitudinal measurements for participants.
Results: The odds of acquiring an upper respiratory infection, adjusted for potential confounders, was estimated to be 0.74 times lower in the treatment group (p = 0.14). The odds of reporting specific symptoms were statistically lower in the treatment arm compared to the placebo arm for runny nose (OR = 0.53, p = 0.01) and cough (OR = 0.51, p = 0.04). Shorter durations of runny nose and cough were also observed in the treatment arm compared to placebo (both p < 0.05). There was no significant difference in severity of symptoms in either group. The observed proportion of reported cold symptoms in the treatment group was lower compared to the placebo group between late January and February in two consecutive cold seasons. Given the physical, workplace and economic impact of upper respiratory infections, this low cost and low risk intervention should be further studied with more robust investigation and meticulous experimental design.