Intake of vitamin C and zinc and risk of common cold: a cohort study

To examine whether intake of vitamin C and zinc is associated with a decrease in the risk of a common cold, we analyzed data from a cohort study carried out in a population of 4,272 faculty and staff from five Spanish universities. Participants were 21-65 years of age, were full-time workers at those universities, and did not have antecedents of asthma or chronic obstructive pulmonary disease. Daily intake of vitamin C and zinc was assessed at baseline by means of a food frequency questionnaire of which the validity and reproducibility were determined in a sample of the population. Subjects were traced for 1 year to detect episodes of common cold, the diagnosis of which was based on symptoms and was validated by additional clinical signs. We detected 1,667 cases of common cold in 79,240 person-weeks of follow-up. Intake of vitamin C and zinc was not related to the occurrence of common cold. Compared with the first quartile of intake, women in the fourth quartile of vitamin C intake showed an adjusted incidence rate ratio of 1.0 (95% CI = 0.7-1.3), and for zinc intake this figure was 1.1 (95% CI = 0.8-1.5). The incidence rate ratios for men in the fourth quartile were 1.1 (95% CI = 0.8-1.4) for vitamin C and 1.3 (95% CI = 0.9-1.8) for zinc.