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VIDARIS is a double blind randomised placebo controlled trial investigating the effect of vitamin D supplementation on the incidence and/or severity of acute respiratory infections-colds and flu in adults.

  • Three hundred and twenty two participants have been recruited from staff and students from the University of Otago Christchurch campus and the Canterbury District Health Board.
  • Each month for 18 months (covering two winters), study participants receive either 100,000 IUs of vitamin D or placebo.
  • Throughout the study duration participants report any instance of cold or flu-like symptoms (sore throat, cough, runny nose, nasal stuffiness) and fill out symptom severity score sheets for up to 14 days for each reported episode.
  • From this, we can determine whether vitamin D supplementation decreases the incidence and/or severity of acute respiratory infections.
  • The trial period was completed in November 2011.

The findings

journal cover - Journal of the American Medical AssociationThe main study findings have been published in the Journal of the American Medical Association (JAMA, 2012; 308(13): 1333-1339).

In brief, over the 18 month trial period participants reported a total of 1204 upper respiratory tract infections (cold/flu-like illnesses).

Of these, 593 were reported by those taking vitamin D (at an average of 3.7 episodes per person over 18 months) and 611 were reported by those taking placebo (at an average of 3.8 episodes per person over 18 months).

The average duration of each cold/flu-like illness was 12 days and the average amount of time off work because of the illness was 0.76 days and was the same irrespective of whether participants were taking vitamin D or placebo.

Therefore, our main finding from VIDARIS is that vitamin D supplementation did not affect the incidence, duration or severity of cold/flu-like illnesses compared with placebo.

Although, we did not find any affect of vitamin D supplementation, the results of the study are still very important as this is the first study to convincingly provide this information.

The results have already attracted international interest and have increased dramatically now the paper is published.

For more information or enquiries contact

Dr Sandy Slow
VIDARIS Co-ordinator
Department of Pathology
University of Otago, Christchurch
PO Box 4345
Christchurch 8140


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