Truswell’s mini-review (1986)

by Harri Hemilä

This text is based on page 45 of Hemilä (2006).
This document has up to date links to documents that are available via the net.
Harri Hemilä
Department of Public Health
University of Helsinki,  Helsinki, Finland

This file is at:

Version May 29, 2012

A. Steward Truswell is an eminent nutritionist who was a co-editor of a major textbook of nutrition (Davidson et al. 1975, 1979), and the author of a popular book ABC of Nutrition, which is currently printed as the fourth edition (Truswell 2003). Truswell (1986) reviewed the vitamin C trials in a letter to the New England Journal of Medicine. The main text of the letter was only half a column long, but a journal with great prestige and a wide circulation makes the statements in Truswell’s mini-review influential and worthy of a critical look. This mini-review was cited in Truswell’s own book on nutrition (2003 p 64) as the only reference to the topic of vitamin C and the common cold.

Truswell did not present any figures or P-values of the original reports, merely providing subjective comments about the trials. Neither did he make any effort to rationalize the great variations in the reported results. For example, on pharmacological grounds it is highly plausible that the effect depends on the dose. Truswell, however, listed the Karlowski et al. trial (1975) in which vitamin C dose was up to 6 g/day and the Dahlberg et al. trial (1944) in which the dose was only 0.05 g/day side-by-side without mentioning that there was a 120-fold discrepancy in vitamin C dosage. Obviously, such trials are not equivalent.

At the end of his mini-review, Truswell stated that "In another five combined trials there appeared to be slight amelioration of symptoms, which was not statistically significant." In fact, the 5 papers cited by Truswell contained 6 trials and not 5 (Table 21; Hemilä 1996a). Furthermore, all 6 trials reported a statistically significant benefit in at least one of the outcomes (Table 21). Thus Truswell’s statement is gravely misleading, even though the 5 papers did contain some other outcomes in which the benefit was not significant statistically. Some further problems in Truswell’s minireview are discussed elsewhere (Hemilä 1996a).

Table 21. 'Five' trials in which the amelioration of common cold symptoms by vitmin C was not statistically significant according to Truswell (1986)

Trial No. of subjects Vitamin C dose (g/d) The effect of vitamin C (%) P [2-tail] Outcome
Karlowski-1975 103 6 -17 0.047 Duration of symptoms
Pitt-1979 674 2 -5 0.023 Severity of symptoms
Ludvigsson-1977a 1 158 1 -39 0.003 Duration of symptoms
Ludvigsson-1977b 1 615 1 -14 0.016 Absense from school
Carr-1981 190 1 -19 <0.05 Duration of symptoms
Wilson-1973 2 128 0.2 -45 0.035 Intensity of symptoms

All 6 trials were placebo-controlled and the effect of vitamin C refers to the difference between the vitamin C and placebo groups. The exact P
values were calculated where appropriate data was available. This table was originally published in Hemilä (1996).
1 Ludvigsson et al. (1977) reported the results of 2 separate trials in the same paper.
2 ‘Whole colds’ among girls administered 0.2 g/day of vitamin C; for details, see the reference.


NOTE: All of the links in the main text should be freely accessible at least as an abstract, but some links below require a permission from publisher for any access.

Carr AB, Einstein R, Lai LYC, et al. (1981b) Vitamin C and the common cold: using identical twins as controls. Med J Aust 2:411-2

Dahlberg G, Engel A, Rydin H (1944) The value of ascorbic acid as a prophylactic against common colds. Acta Med Scand 119:540-61

Davidson S, Passmore R, Brock JF, Truswell AS, eds (1975) Human Nutrition and Dietetics, 6th edn. London: Churchill Livingstone

Davidson S, Passmore R, Brock JF, Truswell AS, eds (1979) Human Nutrition and Dietetics, 7th edn. London: Churchill Livingstone

Hemilä H (1996a) Vitamin C supplementation and common cold symptoms: problems with inaccurate reviews. Nutrition 12:804-9   CH

Karlowski TR, Chalmers TC, Frenkel LD, Kapikian AZ, Lewis TL, Lynch JM (1975) Ascorbic acid for the common cold: a prophylactic and therapeutic trial. JAMA 231:1038-42 

Ludvigsson J, Hansson LO, Tibbling G (1977) Vitamin C as a preventive medicine against common colds in children. Scand J Infect Dis 9:91-8

Pitt HA, Costrini AM (1979) Vitamin C prophylaxis in marine recruits. JAMA 241:908-11

Truswell AS (1986) Ascorbic acid [letter]. N Engl J Med 315:709   BM

Truswell AS (2003) ABC of Nutrition, 4th edn. London: BMJ Books

Wilson CWM, Loh HS, Foster EG (1973) The beneficial effect of vitamin C on the common cold. Eur J Clin Pharmacol 1973;6:26- 32

© 2006-2009 Harri Hemilä. This text is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 

Creative Commons License
Truswell’s mini-review (1986) by Harri Hemilä is licensed under a Creative Commons Attribution 1.0 Finland License.
Based on a work at

Valid HTML 4.01 Transitional