Positive Health Online

Abstract

HEMILA and DOUGLAS, Department of Public Health, University of Helsinki, Finland. Harri.hemila@helsinki.fi. write that over 60 studies have studied the effects of vitamin C on the common cold . The authors review the field (70 references).

Background

Methodology

Results

No effect on common cold incidence was demonstrated in the 6 largest studies, indicating that vitamin C has no preventive effects in normally nourished people in Western countries. However, there are smaller studies reporting benefit, including 3 trials of people under heavy acute physical stress, where incidence of common cold decreased by on average 50%, and in 4 trials with British males, where incidence of common cold decreased by on average 30% in the groups given vitamin C. The authors write that dietary vitamin C intake in the UK is low, and the benefit may be due to the correction of a marginal deficiency, rather than high vitamin doses. Regular vitamin C supplementation (> or = 1 g/day) quite consistently reduced duration of colds ; however the size of the benefit has varied greatly, with duration of cold reduced only by 5% in the 4 largest studies. In two of these studies, however, absence from school and work was reduced by 14-21% per episode, which may be relevant. 3 controlled studies recorded a reduction of at least 80% in pneumonia incidence in the vitamin C group, and one randomised trial reported substantial treatment benefit from vitamin C in elderly UK patients hospitalised with pneumonia or bronchitis.

Conclusion

The preventive effects of supplementation are mainly limited to those with low dietary vitamin C intake; however, therapeutic effects may occur in wider population groups. Further well-designed research studies are required to explore the effects of vitamin C.

References

Hemila H and Douglas RM. Vitamin C and acute respiratory infections. The International Journal of Tuberculosis and Lung Disease 3(9): 756-61. Sep 1999.