Preventative measures to help protect against the common cold virus have traditionally included supplements containing herbs and vitamins, but research into their efficacy has yielded inconsistent results.
Consumers in many Western countries are advised to consumer between five and nine portions of fruit and vegetables a day, but many find these targets hard to achieve.
Researchers from Charite University Medical Centre in Berlin, Germany, set out to investigate the possible preventative effects of a supplement from fruits and vegetables on the common cold.
For their study, published in the British Journal of Nutrition, Stephanie Roll and team used a supplement called Juice Plus+ supplied in powder concentrate by a company called NSA in the United States. The supplement contains vitamins C and E, beta carotene and folate, and previous research has linked it to strengthened immune function.
Their subjects were healthcare professionals, mainly nursing staff, aged between 18 and 65 years
The design was randomised, double-blind and placebo-controlled. The subjects received either four capsules of the supplement per day or a matching placebo for eight months, including a two month run-in period.
The subjects self-reported the number of days with moderate or severe cold symptoms in six months over the winter.
While the mean number of total days with cold symptoms was seen to be the same in the Juice Plus+ group and the placebo group, the former reported a mean of 7.6 days with moderate to severe symptoms.
By contrast, the placebo group reported a mean of 9.5 days with moderate to severe symptoms.
The researchers concluded that the supplement was associate with few days with at least moderate cold symptoms, but they recommended more research to establish whether longer term use could further reduce frequency or severity of colds, and the underlying mechanism.
British Journal of Nutrition (2010)
Reduction of common cold symptoms by encapsulated juice powder concentrate of fruits and vegetables: a randomised, double-blind, placebo-controlled trial.
Authors: Roll, S., Nocon, M., Willich, S.