Reduction of common cold symptoms by encapsulated juice powder concentrate of fruits and vegetables: a randomised, double-blind, placebo-controlled trial

Abstract

Dietary supplements have been suggested in the prevention of the common cold, but previous investigations have been inconsistent. The present study was designed to determine the preventive effect of a dietary supplement from fruits and vegetables on common cold symptoms. In a randomised, double-blind, placebo-controlled trial, healthcare professionals (mainly nursing staff aged 18–65 years) from a university hospital in Berlin, Germany, were randomised to four capsules of dietary supplement (Juice Plus+®) or matching placebo daily for 8 months, including a 2-month run-in period. The number of days with moderate or severe common cold symptoms within 6 months (primary outcome) was assessed by diary self-reports. We determined means and 95 % CI, and differences between the two groups were analysed by ANOVA. A total of 529 subjects were included into the primary analysis (Juice Plus+®: 263, placebo: 266). The mean age of the participants was 39·9 (sd 10·3) years, and 80 % of the participants were female. The mean number of days with moderate or severe common cold symptoms was 7·6 (95 % CI 6·5, 8·8) in the Juice Plus+® group and 9·5 (8·4, 10·6) in the placebo group (P = 0·023). The mean number of total days with any common cold symptoms was similar in the Juice Plus+® and in the placebo groups (29·4 (25·8, 33·0) v. 30·7 (27·1, 34·3), P = 0·616). Intake of a dietary supplement from fruits and vegetables was associated with a 20 % reduction of moderate or severe common cold symptom days in healthcare professionals particularly exposed to patient contact.