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NEWS: Owen Dyer Two strains of the SARS virus sequenced BMJ 2003; 326: 999 [Full text]

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Vitamin C and SARS

Harri Hemilä   (16 May 2003)

Vitamin C and SARS 16 May 2003
Harri Hemilä, lecturer Department of Public Health, University of Helsinki, Finland Send response to journal: Re: Vitamin C and SARS	EDITOR-Recently, the coronavirus was implicated as the cause of the severe acute respiratory syndrome (SARS) (May 10, p 999) (1). In the absence of a specific treatment for SARS, the possibility that vitamin C may show nonspecific beneficial effects on respiratory infections should be considered. The mechanisms whereby vitamin C affects the immune system are not well understood, but there are numerous reports indicating that it may affect the functions of phagocytes, the proliferation of T- lymphocytes, the production of interferon, and the replication of viruses (2). In particular, vitamin C has been shown to increase resistance of chick embryo tracheal organ cultures to infection caused by the avian coronavirus (3). Studies with animals have found that vitamin C modifies susceptibility to various bacterial and viral infections (2). Murphy et al. (4) inoculated marmosets with the parainfluenza virus, after which all control animals (n=7) became infected in three days; only 7 animals in the vitamin C group (n=14), however, became infected (P=0.03; Fisher's exact test, 1-tail). Studies on human subjects have reported decreased levels of vitamin C in plasma, leukocytes, and in urine during various infections, including pneumonia, which suggests that infections affect vitamin C metabolism (2). Placebo-controlled trials have shown quite consistently that the duration and severity of colds are reduced in the vitamin C group (2). Several authors have suggested that vitamin C may hasten convalescence from pneumonia (2), although I am aware of only one randomized trial pertinent to this issue; it was carried out in the UK with elderly patients suffering from pneumonia or bronchitis (5). Therapeutic vitamin C (0.2 g/day) caused a statistically significant decrease in a score of respiratory symptoms in the patients who were most severely ill when admitted to hospital, and a decrease bordering on statistical significance in all patients (5). Furthermore, there were 6 deaths during the trial, all due to respiratory infections: 5 of them in the placebo group (n=29), but only 1 in the vitamin C group (n=28) (P=0.09; Fisher's exact test, 1- tail). The possibility that therapeutic vitamin C supplementation may reduce the severity of respiratory infections seems to warrant further controlled trials, especially in the light of the SARS epidemic. 1 Dyer, O. Two strains of the SARS virus sequenced (news). BMJ 2003;326:999. 2 Hemilä H, Douglas RM. Vitamin C and acute respiratory infections. Int J Tuberc Lung Dis 1999;3:756-61. 3 Atherton JG, Kratzing CC, Fisher A. The effect of ascorbic acid on infection of chick-embryo ciliated tracheal organ cultures by coronavirus. Arch Virol 1978;56:195-9. 4 Murphy BL, Krushak DH, Maynard JE, Bradley DW. Ascorbic acid and its effects on parainfluenza type 3 virus infection in cotton-topped marmosets. Lab Anim Sci 1974;24:229-32. 5 Hunt C, Chakravorty NK, Annan G, Habibzadeh N, Schorah CJ. The clinical effects of vitamin C supplementation in elderly hospitalised patients with acute respiratory infections. Int J Vitam Nutr Res 1994;64:212-19. Competing interests:   None declared