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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.

The common cold is one of the major causes of work absenteeism. Former studies, based on artificial inoculation of rhinovirus, implicated psychological stress in the occurrence of this syndrome, either by increasing susceptibility to the virus or by causing the subject to overrate the perception of the symptoms. Nevertheless, few studies on the effect of stress on the naturally acquired common cold have been conducted. We carried out a 1-year prospective cohort study among the faculty and staff of a Spanish university (N = 1,149). By means of standardized questionnaires, validated in a random sample of the population, we assessed the relation between the occurrence of common cold episodes and exposure to four dimensions of stress: stressful life events, negative affect, positive affect, and perceived stress. All four aspects of stress were related to the occurrence of the common cold. Subjects with a high (fourth quartile) index of negative affect showed an incidence rate ratio of 3.7 (95% confidence interval = 2.2-6.2). The incidence rate ratios for the fourth quartile were 2.5 (95% confidence interval = 1.5-4.1) and 1.9 (95% confidence interval = 1.1-3.2) for perceived stress and stressful events, respectively. A high index of positive affect was associated with an incidence rate ratio of 0.6 (95% confidence interval = 0.3-1.0). These findings suggest that psychological stress is a risk factor for the common cold.