Effect of vitamin C deprivation on the duration of colds in the Sheffield study (1953): a statistical analysis

The Sheffield study on the vitamin C requirement of human adults was carried out in the UK from 1944 to 1946. The main goal was to establish the minimum dose of the vitamin that cures scurvy. The participants were 19 men and 1 woman, aged 21-34; they lived a normal life without strenuous physical work. Evidently the conclusions are limited, given that the majority were male, the age range was small, and the lifestyles were sedentary.

The Sheffield study is small and old, but it is a study of great importance. For example, it is the first reference in the current UK recommendations for vitamin C. For ethical reasons it is highly unlikely that a similar trial will be carried out in the future. Therefore, a critical analysis of the data is important even now. A recent (2022) reanalysis showed that the original conclusions about the impact of vitamin C on scar strength were flawed.

In the study, participants were divided into 3 groups: 10 participants were “deprived” and not given vitamin C supplements (diet contained ~1 mg/day), 7 participants were administered 10 mg/day vitamin C as a supplement, and 3 participants were administered 70 mg/day.

One of the recorded outcomes was the duration of common cold episodes. The statistician for the study (C. H. Jowett) calculated that colds lasted on average 6.4 days during vitamin C deprivation, compared with 3.3 days on the 10-70 mg/day dosage. Thus, deprivation nearly doubled the duration of colds. Jowett concluded that “such evidence as there is, however, definitely confirms the hypothesis that the absence of vitamin C tended to cause colds to last longer” and “the data support the hypothesis that colds of deprived subjects lasted longer, but do not establish it.”

In this paper, the data on common cold duration is reanalyzed. There were 18 cold episodes during vitamin C deprivation, and 21 cold episodes when participants were administered 10-70 mg/day vitamin C.
Vitamin C deprivation increased the duration of colds on average by 77% (P = 0.014).
Vitamin C deprivation decreased the recovery rate from colds by 60% (P = 0.008).
Vitamin C deprivation extended the duration of 1-day colds by 2.2 days (95% CI 1.0 to 5.4 days).

The finding that vitamin C deprivation extended the duration of colds was not reported in the summaries of the trial published in the Lancet (1948) and in the Proceedings of the Nutrition Society (1953). In addition, this finding is also not mentioned in the current UK recommendations for vitamin C. As a consequence, readers have not been fully informed about the common cold results of the Sheffield trial for several decades.