Vitamin C and the common cold: a retrospective analysis of Chalmers' review.

1999

Medical Hypotheses

SUMMARYPlacebo-controlled trials have shown that vitamin C supplementation decreases the duration and severity of common cold infections. However, the magnitude of the benefit has substantially varied, hampering conclusions about the clinical significance of the vitamin. In this paper, 23 studies with regular vitamin C supplementation ( 1 g/day) were analyzed to find out factors that may explain some part of the variation in the results. It was found that on average, vitamin C produces greater benefit for children than for adults. The dose may also affect the magnitude of the benefit, there being on average greater benefit from 2 g/day compared to 1 g/day of the vitamin. In five studies with adults administered 1 g/day of vitamin C, the median decrease in cold duration was only 6%, whereas in two studies with children administered 2 g/day the median decrease was four times higher, 26%. The trials analyzed in this work used regular vitamin C supplementation, but it is conceivable that therapeutic supplementation starting early at the onset of the cold episode could produce comparable benefits. Since few trials have examined the effects of therapeutic supplementation and their results have been variable, further therapeutic trials are required to examine the role of vitamin C in the treatment of colds.

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Vitamin C supplementation and common cold symptoms: factors affecting the magnitude of the benefit

1999

Medical Hypotheses

“…Recently, Chalmers' review was shown to contain serious errors (16). For example, in some cases the data presented were inconsistent with the originally published results.…”

Section: Chalmers' 1975 Reviewmentioning

confidence: 94%

“…Anderson et al's (5) 1972 study was included in the table as the dose during the episodes was 4 g/d although the regular dose was only 1 g/d. Anderson's 1974 study was excluded since there is bias in the distribution of subjects in the study groups (15,16). For the studies by Anderson et al (5) and Pitt and Costrini (12), the days indoors and severity of symptoms, respectively, were selected as outcomes in the calculations.…”

Section: Introductionmentioning

confidence: 99%

Vitamin C supplementation and common cold symptoms: Problems with inaccurate reviews

1996

Nutrition

In 1971, Linus Pauling carried out a meta-analysis of four placebo-controlled trials and concluded that it was highly unlikely that the decrease in the "integrated morbidity of the common cold" in vitamin C groups was caused by chance alone (P < 0.00003). Studies carried out since then have consistently found that vitamin C ( 1 g/d) alleviates common cold symptoms, indicating that the vitamin does indeed have physiologic effects on colds. However, widespread conviction that the vitamin has no proven effects on the common cold still remains. Three of the most influential reviews drawing this conclusion are considered in the present article. Two of them are cited in the current edition of the RDA nutritional recommendations as evidence that vitamin C is ineffective against colds. In this article, these three reviews are shown to contain serious inaccuracies and shortcomings, making them unreliable sources on the topic. The second purpose is to suggest possible conceptual reasons for the persistent resistance to the notion that vitamin C might have effects on colds. Although placebo-controlled trials have shown that vitamin C does alleviate common cold symptoms, important questions still remain.

Vitamin C for preventing and treating the common cold

Rm¹,

Cochrane Database of Systematic Reviews

Chalker³

et al. 2004

Self Cite

163

161

Background The role of oral vitamin C (ascorbic acid) in the prevention and treatment of the common cold has been a subject of controversy for at least sixty years. Public interest in the topic continues to be high and vitamin C continues to be widely sold and used as a preventive and therapeutic agent for this common ailment. Objectives To discover whether oral vitamin C in doses of 200 mg or more daily, reduces the incidence, duration or severity of the common cold when used either as continuous prophylaxis or after the onset of cold symptoms. Search strategy This updated review added to earlier searches, a full search of the following electronic databases: the Central Register of Controlled Trials (CENTRAL) (