Problems with statements by vitamin C experts

by Harri Hemilä

  1. Nutritional authorities
  2. Experts in clinical trials, systematic reviews and nutrition
  3. US nutritional recommendations
  4. UK nutritional recommendations
  5. Textbooks of infectious diseases
  6. Bias against vitamin C

This text is based on pages 61-62 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:

Version May 29, 2012

... Since then I never pay any attention to anything by ‘experts.’
I calculate everything myself.
I’ll never make that mistake again, reading the experts’ opinions.
Of course, you only live one life, and you make all your mistakes,
and learn what not to do, and that’s the end of you.

    Richard Feinman, 1985
    “Surely You're Joking, Mr. Feinman”

Have no respect whatsoever for authority; forget who said it and instead look at what he starts with, where he ends up, and ask yourself, “is it reasonable?”

    Richard Feinman, 1988
    “What Do You Care What Other People Think?”

When an old and distinguished person speaks to you, listen to him carefully - and with respect but do not believe him. Never put your trust in anything but your own intellect. Your elder, no matter whether he has grey hair or has lost his hair, no matter whether he is a Nobel Laureate, may be wrong. The world progresses, year by year, century by century, as the members of the younger generation find out what was wrong among the things that their elders said. So you must always be skeptical - always think for yourself.
    There are, of course, exceptional circumstances: when you are taking an examination, it is smart to answer the questions not by saying what you think is right, but rather what you think the professor thinks is right.

    Linus Pauling, 1955
    Advice to Students

I wish to propose for the reader’s favourable consideration a doctrine which may, I fear, appear wildly paradoxical and subversive. The doctrine in question is this: that it is undesirable to believe a proposition when there is no ground whatever for supposing it true, I must, of course, admit that if such an opinion became common it would completely transform our social life and our political system; since both are at present faultless, this must weight against it. I am also aware (what is more serious) that it would tend to diminish the incomes of clairvoyants, bookmakers, bishops and others who live on the irrational hopes of those who have done nothing to deserve good fortune here or hereafter.

    Bertrand Russell, 1928
    Sceptical Essays

… Where I have been necessarily led, in this disagreeable part of the work, to criticise the sentiments of eminent and learned authors, I have not done it with a malignant view of depreciating their labours, or their names; but from a regard to truth, and to the good of mankind. I hope such motives will, to the candid, and to the most judicious, be a sufficient apology for the liberties I have assumed.

    James Lind, 1753
    A Treatise of the Scurvy

The status of an ‘expert’ implies that an individual is thoroughly familiar with the particular field. Unfortunately, in the vitamin C field, the track record of many experts is poor.

Nutritional authorities

James A Olson, Robert E Hodges, and Victor Herbert (see Safety) were all members of the first committee preparing the 10th edition of the US RDA nutritional recommendations, which plays a central role in US governmental policy, and indirectly affects policy in numerous other counties (FNB 1989a). James A. Olson was also an editor of a major textbook on nutrition (Shils, Olson, et al. 1994, 1999). The review of vitamin C by Olson and Hodges (1987), which contained the anecdotal stories of vitamin C toxicity (see Safety), was planned as the vitamin C section of the 10th edition of the RDA recommendations (Olson 1986; Pellett 1988). The US National Academy of Sciences decided, however, not to publish the RDA draft by the first committee because of an impasse resulting from scientific differences of opinion between the first committee and the scientific reviewers appointed by the National Academy of Sciences (Press 1985; Marshall 1985). One reason for the disagreements was the proposal that the RDA level for vitamin C recommendation be lowered from 60 mg/day to 40 mg/day for men and 30 mg/day for women. The second RDA committee kept the vitamin C level at 60 mg/day for both men and women (FNB 1989a).

Victor Herbert, who reiterated the anecdotal stories of vitamin C toxicity (see Safety) in one of his papers (Herbert 1993), was also a member of the committee preparing the 9th edition of the US RDA nutritional recommendations (FNB 1980). Herbert received the 1972 McCollum Award for outstanding scientific accomplishment in the field of nutrition (Anonymous 1973), and was the president of the American Society for Clinical Nutrition in 1980-1981. In 1984 Herbert received the FDA Commissioner’s Special Citation Award for "outstanding and consistent contributions against the proliferation of nutrition quackery to the American consumer" (Halsted 2003; Oransky 2003: Scott 2004). In his reminiscences Pauling described an acrimonious exchange of letters with Victor Herbert who rejected the results of all placebo-controlled trials on vitamin C and the common cold without any reasonable argument. Pauling commented that "I finally became sufficiently irritated by this fellow that I decided I ought to do something about it. So I sat down one summer and in two months wrote a book, Vitamin C and the Common Cold " (Marinacci 1995 pp 248-51). In this respect Herbert was, paradoxically, indirectly behind the increase in the popular enthusiasm for vitamin C supplementation that resulted from Pauling’s book. The current author pointed out that Herbert’s conclusions (1993), that there is no reliable data to show that vitamin C supplementation may provide any benefit and that vitamin C supplements may instead be highly harmful, were based on a grossly biased selection of references (Hemilä 1994b).

Stephen Barrett (2007) has written several books on nutritional quackery (Barrett 1980; Barrett & Herbert 1994), and received the FDA Commissioner’s Special Citation in 1984 for "outstanding and consistent contributions against the proliferation of nutrition quackery to the American consumer." Barrett also received the 2001 Distinguished Service to Health Education Award from the American Association for Health Education. However, Barrett’s presentation of facts related to the findings from studies on vitamin C and the common cold have been markedly biased. In a comment on Barrett’s paper (1995) claiming there is no evidence that vitamin C might affect colds, Hemilä (1995b) pointed out that "Anderson et al. (1972) found that vitamin C supplementation (1-4 g/ day) decreased the ‘numbers of days confined to house’ per subject by 48% in subjects with a low dietary intake of fruit juices [see Hemilä 2006 Table 13, p 35]. Barrett’s claim that at best there is only a slight reduction in symptoms appears grossly misleading considering the published results." Stephen Barrett replied to this that "Anderson’s first study found … a 30% difference." In a subsequent letter Edgar Villchur (1995) pointed out that "Barrett’s reply in the same issue challenges Hemilä’s reporting accuracy, but Hemilä is correct … Barrett, however, doesn’t say he is citing a different part of the Anderson data, and thus makes it seem that Hemilä has either misread or misrepresented Anderson." In a reply to this accusation, Stephen Barrett (1995) conceded that "Villchur is correct that Hemilä and I referred to different figures."

Experts in clinical trials, systematic reviews and nutrition

Thomas Chalmers, Paul Meier, A. Steward Truswell, and Jos Kleijnen are experts in controlled trials, medical statistics, nutrition, and systematic reviews, yet their reviews on vitamin C and the common cold contain lots of factual errors and misleading statements (see Hemilä 2006 pp 36-45; problems in reviews). The Chalmers (1975) and Dykes and Meier (1975) reviews were cited in major textbooks of infectious diseases and in the US RDA recommendations, although some of the numerous shortcomings of both reviews should have been apparent to any expert even superficially familiar with the original study reports.

US nutritional recommendations

In the most recent US nutritional recommendations (FNB 2000 pp 126-7), Chalmers’ review (1975) and the Hemilä and Herman criticism (1995; see Criticism) of Chalmers’ review are cited in the same paragraph without mentioning that the latter paper shows that the former review is invalid. Thus, the experts writing the vitamin C chapter did not read or understand the two papers cited to see that they were incompatible. Although the most recent recommendations extensively discuss the observational studies related to the possibility that vitamin C intake might affect chronic diseases, the recommendations ignore some 40 placebo-controlled trials that have examined the preventive effect of vitamin C on colds (FNB 2000 p 117, p 127; Douglas, Hemilä, et al. 2007). Only 4 controlled trials are cited in the US recommendations (Peters et al. 1993; Coulehan et al. 1976; Miller et al. 1977; Ludvigsson et al. 1977). Since the Ludvigsson et al. trial (1977) mentioned in the recommendationsis is only one of the 6 largest (Hemilä 1997) , 83% (5/6) of the largest common cold trials are simply ignored, and some 90% of all the placebo-controlled trials on vitamin C and the common cold are ignored in the current US nutritional recommendations.

Even in the case of the Ludvigsson paper (1977), the study findings are disregarded in the recommendations (FNB 2000 p 127). Ludvigsson et al. (1977) found a 14% reduction (P = 0.008) in the duration of ‘absence from school because of upper respiratory tract infection’ in the main trial, and a 39% reduction (P = 0.002) in the duration of ‘upper respiratory tract infection’ in the smaller trial, but these findings are not mentioned in the recommendations. Two large trials reporting that vitamin C supplementation significantly increased the proportion of participants who remained free of illness during supplementation (Hemilä 2006 Table 20, p 44) are not cited in the recommendations either, or any of the UK trials that found a significant proportion of participants benefiting when the outcome is ≥2 colds during the trial (Hemilä 2006 Table 22, p 47). Neither were any of the 3 trials that found a significant reduction in pneumonia incidence by vitamin C supplementation (Hemilä 1997; Hemilä and Louhiala 2007) mentioned in the recommendations. It is not clear to what extent the poor coverage of literature is caused by lack of knowledge of the studies, and how much by an intentional decision to discard studies that do not fit with a preconception that vitamin C is useless for colds and other respiratory infections.

In systematic reviews it is essential to cover the published studies widely and analyze the results objectively (Ian Chalmers & Altman 1995; Higgins & Green 2006), but this was not done in the most recent US nutritional recommendations (FNB 2000). Although the common cold trials do not allow explicit conclusions to be drawn about what might be the best doses of vitamin C intake, the published trials do show that large doses affect common cold severity and duration in large groups of people, and the incidence of colds in some people. Objective discussion of the common cold trials also provides justification to carry out further study, and to use susceptibility to and severity of infections as potential outcomes of interest in considering the ‘optimal intake levels’ instead of focusing only on cancers and cardiovascular diseases, and using ‘maximal neutrophil concentration with minimal urinary loss’ as a surrogate with no established validity against clinically relevant outcomes.

The problems of expert reliability in nutritional recommendations are also seen in other vitamin C issues. In the 10th edition of RDA, comments on vitamin C and cholesterol metabolism were based on 2 trials that did not use placebo-control (FNB 1989a pp 120-1), and 3 placebo-controlled studies which found a significant decrease in elevated cholesterol levels with vitamin C supplementation were disregarded (Hemilä 1992c1993).

UK nutritional recommendations

Similar problems are faced in the UK nutritional recommendations (DH 1991 [see Hemilä 1997d]), where no mention is made of the possible role of vitamin C on the common cold, although some 40 placebo-controlled trials have been carried out. Furthermore, one of the trials cited in the UK recommendations did report that the geometric mean duration of colds was 6.4 days in vitamin C-deprived subjects and 3.3 days in non-deprived subjects. The authors 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" (Bartley, Krebs & O’Brien 1953 p 43), but the authors of the UK recommendations disregarded this (DH 1991). The brief discussion of the vitamin C and cholesterol issue referred to a single uncontrolled intervention study, and disregarded 11 published placebo-controlled trials (DH 1991; Hemilä 1992c, 1997d).

Textbooks of infectious diseases

In the most recent editions of Mandell et al.’s textbook of infectious diseases (Gwaltney 2000, 2005), Chalmers’ review (1975) is no longer cited; however, comments on vitamin C and the common cold are based on 2 small trials with artificially inoculated colds (Walker et al. 1967; Schwartz et al. 1973). These 2 trials recorded only 36 and 21 common cold episodes respectively, whereas none of the 5 large-scale trials recording over 1,000 natural common cold episodes per trial (Hemilä 2006: Table 14) is cited (Gwaltney 2000, 2005). In a classic paper, Thomas Chalmers pointed out that negative findings from small trials may correspond to the type II error in statistics and concluded that "Concern for the probability of missing an important therapeutic improvement because of small sample sizes deserves more attention in the planning of clinical trials" (Freiman et al. 1979). Thus, drawing conclusions from trials with 36 and 21 common cold episodes may lead to a false negative conclusion. Furthermore, it is possible that natural colds differ from artificially induced colds. The rate of the former is about 1 per year or 0.02 per week for adults, whereas the rate of the latter was 0.4 to 1.0 per week (Walker et al. 1967; Schwartz et al. 1973), indicating that the exposure level to viruses was orders of magnitude higher in the artificially inoculated colds, which may affect the role of vitamin C.

Bias against vitamin C

Pauling (1971b, 1976a pp 121-38, 1986a pp 225-36) also provided several examples of how the authorities in nutrition misinterpreted and ignored the findings of published trials. Evidently, a personal problem for Pauling was that "Medical experts have a long history of resisting scientific innovations from what they define as ‘the outside’ " (Barber 1961).

The poor quality of expert comments on vitamin C and the common cold is puzzling. Goodwin and Tangum (1998) provided several examples to support the conclusion that there has been systematic bias against the concept that vitamins might be beneficial in levels higher than the minimum required to avoid classic deficiency diseases: "Throughout much of the 20th century, American academic medicine was resistant to the concept that micronutrient supplementation might prove beneficial. This resistance is evident in several ways: (1) by uncritical acceptance of bad news about micronutrient supplements; reports of toxic effects were rarely questioned and widely quoted; (2) by the scornful, dismissive tone of the discussions about micronutrient supplementation in textbooks of medicine, a tone avoided in most medical controversies; and (3) by the skeptical reaction greeting any claim of efficacy of a micronutrient, relative to other therapies; indeed, most claims were simply ignored."

Bias against vitamin C was also documented by Richards (1988, 1991; Galloway 1991; Huxtable 1992; Segerstråle 1992) who compared the attitudes and arguments of physicians to three putative cancer medicines: 5-fluorouracil, interferon, and vitamin C.

The evaluation of the potential effectiveness of a therapeutic method usually depends greatly on the possibility of biologically rationalizing the method. Goodwin and Goodwin (1981, 1984) reviewed several cases in which an effective method of treatment was erroneously rejected due to a lack of understanding of the physiological mechanism of the effect. They designated this problem ‘the tomato effect’, since the tomato was considered poisonous in the USA in the 1700s because several other plants in the same family were poisonous: "The tomato effect in medicine occurs when an efficacious treatment for a certain disease is ignored because it does not ‘make sense’ in the light of accepted theories of disease mechanism and drug action." Thus, the question of evaluating a new method of therapy is not just whether a moderate effect is reproducible in controlled trials, but substantially depends on conceptual issues related to the biological explanations (Vandenbroucke 1998a; Vandenbroucke & de Craen 2001). It is possible, for example, that the claim in the biochemistry textbooks that vitamin C participates in the hydroxylation of proline in collagen (Berg et al. 2002) leads to a misleading impression of the mechanism of vitamin C action, as the effects of vitamin C on other biochemical reactions (Englard & Seifter 1986; Padh 1990) and on the immune system (Hemilä 1997a, 2003a) are not mentioned at all. Some further possible conceptual reasons for the bias against the effects of vitamin C on common cold have been discussed elsewhere (Hemilä 1996a, 1997a).


NOTE: All 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.

Anderson TW, Reid DBW, Beaton GH (1972) Vitamin C and the common cold: a double-blind trial. Can Med Assoc J 107:503-8

Anonymous (1973) McCollum Award: Victor D. Herbert. Am J Clin Nutr 26:907-9

Barber B (1961) Resistance by scientists to scientific discovery. Science 134:596-602

Barrett S (1980) The Health Robbers: How to Protect Your Money and Your Life, 2nd edn. Philadelphia, PA: George F Stickley

Barrett S (1995) The dark side of Linus Pauling’s legacy. Skeptical Inquirer 19(1; Jan/Feb):18-20; slightly revised version: (2001) * comments in: Hemilä (1995b) 

Barrett S (2007) 

Barrett S, Herbert V (1994) The Vitamin Pushers: How the Health Food Industry Is Selling America a Bill of Goods. Amherst, NY: Prometheus

Chalmers TC (1975) Effects of ascorbic acid on the common cold: an evaluation of the evidence. Am J Med 58:532-6

Chalmers I, Altman DG, eds (1995) Systematic Reviews. London: BMJ Publishing Group 

Coulehan JL, Eberhard S, Kapner L, et al. (1976) Vitamin C and acute illness in Navajo schoolchildren. N Engl J Med 295:973-7

DH [Department of Health] (1991) Vitamin C. In: Dietary Reference Values for Food Energy and Nutrients for the United Kingdom. Report of the Panel of Dietary Reference Values of the Committee on Medical Aspects of Food Policy. Rep Health Soc Subj (Lond) 41:117-22 London: HMSO

Douglas RM, Hemilä H, Chalker EB, Treacy B (2007) Vitamin C for preventing and treating the common cold [systematic review]. Cochrane Database  Syst Revs (4): CD000980     Cochrane Org

Dykes MHM, Meier P (1975) Ascorbic acid and the common cold: evaluation of its efficacy and toxicity. JAMA 231:1073-9

Englard S, Seifter S (1986) The biochemical functions of ascorbic acid. Annu Rev Nutr 6:365-406 

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FNB [Food and Nutrition Board, Institute of Medicine] (2000) Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium and Carotenoids. Washington DC: National Academy Press  vitamin C pp 95-185  

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Goodwin JS, Goodwin JM (1981) Failure to recognize efficacious treatments: a history of salicylate therapy in rheumatoid arthritis. Persp Biol Med 31:78-92

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Goodwin JS, Tangum MR (1998) Battling quackery: attitudes about micronutrient supplements in American Academic medicine. Arch Intern Med 158:2187-91

Halsted CH (2003) Victor Herbert MD, 1927-2002. Am J Clin Nutr 77:757-9  *  see also: 

Hemilä H (1992c) Vitamin C and plasma cholesterol. Crit Rev Food Sci Nutr 32:33-57

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Hemilä H (1997) Vitamin C intake and susceptibility to the common cold. Br J Nutr 77:59-72

Hemilä H (1997a) Vitamin C and infectious diseases. In: Vitamin C in Health and Disease [Packer L, Fuchs J, eds]. NY: Marcel Dekker. pp 471-503    other extract

Hemilä H (1997d) Vitamin C intake and susceptibility to the common cold – Reply. Br J Nutr 78:861-6 

Hemilä H (2003a) Vitamin C, respiratory infections, and the immune system. Trends Immunol 11:579-80

Hemilä H, Herman ZS (1995) Vitamin C and the common cold: a retrospective analysis of Chalmers’ review. J Am Coll Nutr 14:116-23

Hemilä H, Louhiala P (2007) Vitamin C for preventing and treating pneumonia. Cochrane Database  Syst Rev (1):CD005532

Herbert V (1993) Does mega-C do more good than harm, or more harm than good? Nutr Today 28(1):28-32  

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Pellett PL (1988) The R.D.A. controversy revisited. Ecol Food Nutr 21:315-20

Peters EM, Goetzsche JM, Grobbelaar B, Noakes TD (1993) Vitamin C supplementation reduces the incidence of postrace symptoms of upper-respiratory-tract infection in ultramarathon runners. Am J Clin Nutr 57:170-4

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Copyright: © 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.  

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