ArticlePDF Available

Cochrane review: Vitamin C for preventing and treating the common cold

  • Australian National University(


Background The role of vitamin C (ascorbic acid) in the prevention and treatment of the common cold has been a subject of controversy for 60 years, but is widely sold and used as both a preventive and therapeutic agent.Objectives To discover whether oral doses of 0.2 g or more daily of vitamin C reduces the incidence, duration or severity of the common cold when used either as continuous prophylaxis or after the onset of symptoms.Search strategyWe searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 4, 2006); MEDLINE (1966 to December 2006); and EMBASE (1990 to December 2006).Selection criteriaPapers were excluded if a dose less than 0.2 g per day of vitamin C was used, or if there was no placebo comparison.Data collection and analysisTwo review authors independently extracted data and assessed trial quality. 'Incidence' of colds during prophylaxis was assessed as the proportion of participants experiencing one or more colds during the study period. 'Duration' was the mean days of illness of cold episodes.Main resultsThirty trial comparisons involving 11,350 study participants contributed to the meta-analysis on the relative risk (RR) of developing a cold whilst taking prophylactic vitamin C. The pooled RR was 0.96 (95% confidence intervals (CI) 0.92 to 1.00). A subgroup of six trials involving a total of 642 marathon runners, skiers, and soldiers on sub-arctic exercises reported a pooled RR of 0.50 (95% CI 0.38 to 0.66).Thirty comparisons involving 9676 respiratory episodes contributed to a meta-analysis on common cold duration during prophylaxis. A consistent benefit was observed, representing a reduction in cold duration of 8% (95% CI 3% to 13%) for adults and 13.6% (95% CI 5% to 22%) for children.Seven trial comparisons involving 3294 respiratory episodes contributed to the meta-analysis of cold duration during therapy with vitamin C initiated after the onset of symptoms. No significant differences from placebo were seen. Four trial comparisons involving 2753 respiratory episodes contributed to the meta-analysis of cold severity during therapy and no significant differences from placebo were seen.Authors' conclusionsThe failure of vitamin C supplementation to reduce the incidence of colds in the normal population indicates that routine mega-dose prophylaxis is not rationally justified for community use. But evidence suggests that it could be justified in people exposed to brief periods of severe physical exercise or cold environments.Plain language summaryVitamin C for preventing and treating the common coldThe term 'the common cold' does not denote a precisely defined disease, yet the characteristics of this illness are familiar to most people. It is a major cause of visits to a doctor in Western countries and of absenteeism from work and school. It is usually caused by respiratory viruses for which antibiotics are useless. Other potential treatment options are of substantial public health interest.Since vitamin C was isolated in the 1930s it has been proposed for respiratory infections, and became particularly popular in the 1970s for the common cold when (Nobel Prize winner) Linus Pauling drew conclusions from earlier placebo-controlled trials of large dose vitamin C on the incidence of colds. New trials were undertaken.This review is restricted to placebo-controlled trials testing at least 0.2 g per day of vitamin C. Thirty trials involving 11,350 participants suggest that regular ingestion of vitamin C has no effect on common cold incidence in the ordinary population. It reduced the duration and severity of common cold symptoms slightly, although the magnitude of the effect was so small its clinical usefulness is doubtful. Nevertheless, in six trials with participants exposed to short periods of extreme physical or cold stress or both (including marathon runners and skiers) vitamin C reduced the common cold risk by half.Trials of high doses of vitamin C administered therapeutically (starting after the onset of symptoms), showed no consistent effect on either duration or severity of symptoms. However, there were only a few therapeutic trials and their quality was variable. One large trial reported equivocal benefit from an 8 g therapeutic dose at the onset of symptoms, and two trials using five-day supplementation reported benefit. More therapeutic trials are necessary to settle the question, especially in children who have not entered these trials.
Evid.-Based Child Health 3: 723 728 (2008)
Published online in Wiley InterScience ( DOI: 10.1002/ebch.261
Commentaries on ‘Vitamin C for preventing and treating
the common cold’ with responses from the review author
Larissa Shamseer,1Sunita Vohra,1* Renske Bax,2** Leo Spee,2Marieke Madderom2and Harri Hemil¨
1CARE Program, Department of Pediatrics, Faculty of Medicine and School of Public Health, University of Alberta, Edmonton, Canada
2Department of General Practice, Erasmus MC-University Medical Center, Rotterdam, The Netherlands
3Department of Public Health, University of Helsinki, Finland
These are commentaries on a Cochrane review, published in this issue of EBCH, first published as: Douglas
RM, Hemil¨
a H, Chalker E, Treacy B. Vitamin C for preventing and treating the common cold. Cochrane
Database of Systematic Reviews 2007, Issue 3. Art. No.: CD000980. DOI: 10.1002/14651858.CD000980.
Further information for this Cochrane review is available in this issue of EBCH in the accompanying EBCH
Summary and Characteristics and Key Findings Tables.
Larissa Shamseer and Sunita Vohra’s
Despite dozens of clinical studies with conflicting or
inconclusive results, vitamin C is frequently touted as
the natural ‘fix’ for upper respiratory tract infections
(URTI). In their recent Cochrane systematic review,
Douglas et al. (1) report that while prophylactic vita-
min C did not significantly reduce the incidence or
severity of the common cold, it reduced mean cold
duration by 8% in adults [95% Confidence Intervals
(CI) 3–13%] and 13.6% in children (95% CI 5–22%).
When used as treatment, vitamin C was reported to
have no significant effect on duration or severity of
The common cold affects people worldwide and is
likely the most common illness known. There is no
known cure and it is associated with substantial eco-
nomic loss (2). The incidence and prevalence of the
common cold are difficult to estimate as most affected
do not seek medical care, making tracking through
health care utilization difficult. While the use of con-
ventional over-the-counter medications may be easily
measured using financial reports, utilization of natu-
ral health products (NHPs) is more challenging since
a given product may have multiple potential clinical
indications. In Canada, NHPs are defined as vitamins,
*Correspondence to: Sunita Vohra, 8223B Aberhart Centre #1, Uni-
versity of Alberta, Edmonton, Alberta, Canada T6G 2J3.
** Correspondence to: Renske Bax, Department of General Practice,
Room Ff322, Erasmus Medical College, University Medical Center
Rotterdam, PO Box 2040, 3000CA, Rotterdam, The Netherlands.
*** Correspondence to: Harri Hemil ¨
a, Department of Public Health,
University of Helsinki, FIN-00014, Finland.
minerals, herbal remedies, homeopathic remedies, tra-
ditional medicines, probiotics and other products like
amino acids and essential fatty acids that are manu-
factured, sold, or represented for use in the diagnosis,
treatment or prevention of a disease or disorder, for
restoring or correcting organic functions or for mod-
ifying organic functions in a manner that maintains
and/or promotes health (3). NHPs are most often used
by the public as self-care and interest into their safety
and efficacy is increasing: to date there have been at
least five published Cochrane protocols or completed
reviews on NHPs for the common cold (1,4–7).
This large and timely review addresses the impor-
tant question of whether oral doses of 0.2 g or more
daily of vitamin C reduce the incidence, duration or
severity of the common cold when used either as con-
tinuous prophylaxis or after the onset of symptoms. To
aid in interpretation of these findings, we would like
to draw attention to three key variables in the review:
study inclusion criteria, choice of databases searched,
and the generalizability of the included studies. The
authors’ decision to limit included trials to those that
could be ‘methodologically assessed using the Jadad
quality score’ is unusual, since virtually any trial
should be assessable using the Jadad scale. Although
they state that ‘study quality was not used as an exclu-
sion criterion’, nor were any trials excluded on this
basis, it is worth noting that 46 out of 56 included stud-
ies were on the mid-high end of the quality continuum
with Jadad quality ratings 3 (8). Choice of included
studies is difficult to interpret due to the absence of
assessment or discussion of publication bias.
Publication bias is particularly important to assess
in studies of complementary and alternative medicine
(CAM), an umbrella term which includes NHPs.
Copyright 2008 John Wiley & Sons, Ltd.
724 L. Shamseer, S. Vohra, R. Bax, L. Spee, M. Madderom and H. Hemil¨
Unlike conventional medicine, in which high qual-
ity, positive findings are most frequently published in
leading, high-impact journals (9), the reverse occurs in
CAM research: high quality, negative studies are more
likely to get published in the same journals (10 12).
Further, it is well-known that CAM journals are less
likely to be indexed in mainstream databases, such
as those examined in this review, than conventional
medical journals (13). In fact, one study examining
publication location of CAM RCTs found that the
Commonwealth Agriculturall Bureaux (CAB Health),
Cumulative Index to Nursing and Allied Health Lit-
erature (CINAHL) and Allied and Complementary
Medicine Database (AMED) databases contain unique
material not available from MEDLINE and EMBASE
(14). None of the included studies in this review are
from CAM journals; all are from conventional medi-
cal journals, the majority of which are higher impact
journals. This may mean that more studies with neg-
ative results have been systematically included for
analysis, thereby contributing to the lack of signifi-
cant positive effect for all but one primary outcome.
The authors also failed to mention whether foreign lan-
guage studies were sought, identified, or included in
the review, also potentially contributing to publication
bias. Unfortunately, the absence of a funnel plot to
delineate if and where publication bias exists, and the
choice of databases searched for this review renders
its findings difficult to interpret.
The findings of this review are particularly impor-
tant to children, given their high prevalence of the
common cold and pediatric NHP use in North Amer-
ica. The Center for Disease Control and Prevention
estimates that there is an annual loss of 22 million
school days due to the common cold in the United
States (15). The National Institute of Allergy and
Infectious Disease estimates that children experience
between 6 and 10 colds per year, likely due to
their close proximity in the school setting (16). With
regards to NHP utilization, use among children is
widespread up to 35% reportedly use NHPs, most
commonly vitamins and botanical products (17,18).
By 2005, at least 24 RCTs of vitamin C for illnesses
including the common cold had been identified in pop-
ulations including children (19). Therefore it is quite
evident that vitamin C is already of high interest and
use in pediatric populations. Douglas et al. presented
subgroup analysis for children for only one of five
primary outcomes (i.e. the effect of vitamin C admin-
istered before cold onset on duration), when all would
have been of potential interest and relevance to this
Finally, it is important to note that the included
trials were primarily conducted in developed countries,
perhaps representing differences in terminology used
to describe the common cold worldwide. Given the
differences in nutritional status between developing
countries and those included in the review, caution
should be applied when generalizing its results.
Overall, the findings of the review demonstrate that
in developed countries, vitamin C may not prevent
the common cold, but may have a modest effect in
reducing cold duration when taken prophylactically.
For a benign self-limited condition such as the com-
mon cold, careful consideration of the risk : benefit
ratio is warranted. Its effect seems most promising in
as prophylaxis in very physically active individuals.
For the general population, if vitamin C’s only effect
is a modest reduction in the duration of cold symp-
toms, and to achieve this effect, a daily prophylactic
dose is required, it may not warrant further consid-
eration. A definitive answer may require additional
well-designed trials in this area, particularly those that
examine for potential dose-effect, as a recurring crit-
icism of NHP research is the study of inappropriate
doses, leading to erroneous conclusions about efficacy.
Future systematic reviews should include a broader
range of databases, inclusion of CAM journals and
careful examination for the effects of publication bias.
In the absence of such data, given the modest effect
sizes currently reported, it is premature to prescribe
vitamin C to prevent or treat URTI.
Declaration of Interest
Sunita Vohra receives salary support from the Alberta
Heritage Foundation for Medical Research and the
Canadian Institutes of Health Research.
Response from the Review Author to the
Commentary by Shamseer and Vohra
I share Shamseer and Vohra’s concern about publica-
tion bias in the leading medical journals. For example,
in 1975 the American Journal of Medicine published
a highly influential review on vitamin C and the com-
mon cold by Thomas Chalmers (20). When I became
interested in the same topic, I was puzzled by the
great discrepancy between the original trial reports and
Chalmers’ selection and description of them. I wrote
a critique of Chalmers’ review, but my paper was
rejected by the same journal and it was published in a
minor journal (21,22). Obviously, the leading journals
must be highly selective in the acceptance of papers,
but that leads to bias in reports reaching wide reader-
Nevertheless, I do not agree that publication bias
might substantially affect the main conclusions of our
Cochrane review (1). We drew several conclusions
and they should be considered individually. We con-
cluded that there is strong evidence of heterogeneity
in the effect of vitamin C on common cold incidence.
Vitamin C halved the number of colds in participants
under heavy acute physical stress, but had no effect
on the incidence of colds in the general community.
How could such heterogeneity be generated by publi-
cation bias? Furthermore, based on 30 trials with 9,676
Copyright 2008 John Wiley & Sons, Ltd. Evid.-Based Child Health 3: 723 –728 (2008)
DOI: 10.1002/ebch.261
Commentaries on ‘Vitamin C for Preventing and Treating the Common Cold’ 725
recorded common cold episodes in all, we concluded
that regular vitamin C supplementation shortens the
duration of colds. The proposal that this effect is
explained by publication bias presumes that several
large trials with negative findings remain unpublished,
which does not seem a reasonable assumption. Pub-
lication bias may affect the point estimates of our
analyses, but it is unlikely to affect our main con-
Shamseer and Vohra comment that we might have
included more data bases in our literature searches.
However, even though MEDLINE and EMBASE can
miss some trials published in CAM journals, we also
searched the Cochrane CENTRAL which collects tri-
als independent of them being recorded in MED-
LINE or EMBASE. Furthermore, we describe in the
Cochrane review that I have been actively collecting
literature on vitamin C and common cold trials for over
two decades. Because of my familiarity with the liter-
ature, I pointed out that an extensive literature search
(23,24) had missed six placebo-controlled trials (25).
If Shamseer and Vohra consider that we may have
missed relevant trials, they should search and describe
examples instead of just speculating. Furthermore, as
described above, our main conclusions are not sensi-
tive to a few unidentified or unpublished trials.
Shamseer and Vohra state that we did not men-
tion whether foreign language trials were sought and
included. We did not describe selection by language
which means that we selected trials independent of
their language. The reference section of our review
shows that we found and assessed trials published in
Finnish, German, Spanish and Swedish.
Shamseer and Vohra argue that we should have
constructed a funnel plot to explore the possibility
of publication bias. Funnel plot has been popular;
however, it is not a valid method. For example, dif-
ferent metrics lead to different shapes of the funnel
plot. Furthermore, asymmetry can arise from biologi-
cal heterogeneity so that asymmetry is no evidence of
publication bias. Because of various problems, the use
of the funnel plot has been strongly discouraged (26).
In fact, our Cochrane review serves as a good example
against the funnel plot. The six trials with participants
under heavy acute physical stress, which found that
vitamin C halved the number of colds, are all small.
In a funnel plot of all 30 trials measuring incidence,
these six small trials would lead to asymmetry. Thus,
the funnel plot would ‘explain’ the positive findings by
publication bias, which would discourage further trials.
In contrast, our subgroup analysis in which the pos-
itive results are explained by the special participants
and conditions suggests direction for further research
to test a justified hypothesis.
Shamseer and Vohra notice that we presented sub-
group analysis for children for only one of five primary
outcomes. In the incidence analysis, statistically sig-
nificant heterogeneity disappeared when we divided
trials to those with participants under acute physical
stress and to those with participants of the general
community. Trials with children are consistent with the
pooled estimates of these two subgroups. The largest
trial with children of the general community, by Lud-
vigsson et al. with 615 Swedish schoolchildren (27),
found no effect by vitamin C on common cold inci-
dence consistent with the adult trials in the general
community. The single trial with children under acute
physical stress, by Ritzel at a skiing school in the
Swiss Alps (28), found 45% (95% CI: 5 68%) reduc-
tion in common cold incidence consistent with five
trials with adults. Another outcome was the severity
of colds in regular supplementation trials. We divided
trials to two subgroups by the outcome: severity mea-
sured by a severity score and by the mean days off
work or school (p=0.004 for the benefit of vitamin C
over placebo in the two subgroups with 15 trials). The
complex outcome and the limited number of trials did
not allow further subgroup analyses. Two outcomes
were restricted to therapeutic trials and we state that
‘none of the therapeutic trials examined the effect of
vitamin C on children’. Thus, there are clear reasons
why we presented subgroup analysis for children for
only one of the five outcomes.
I agree with Shamseer and Vohra’s comment that
generalizing our results is hampered by the fact that
most of the trials were carried out in developed
countries. On the other hand, a group of four trials
in the UK with schoolboys and male students found a
30% (95% CI 19–40%) reduction in common cold
incidence by vitamin C supplementation (29). This
subgroup is mentioned in our discussion, but two
of the trials used doses less than 200 mg/day and
were therefore excluded from the Cochrane analyses.
Nevertheless, as regards the developing countries, this
group of trials is interesting, because at the time of
those four trials the dietary vitamin C intake in the
UK was substantially lower than in other western
countries and might have been suboptimal (29). A
Canadian trial with adults also suggested that vitamin
C supplementation effect might be modified by dietary
vitamin C intake (30). ‘Days confined to house per
subject’ was reduced by 48% in participants who had
low intake of fruit juices and by 22% in those who had
high intake of juices; vitamin C dosage was 1 g/day
regularly and 3 g/day extra during colds (30). Thus,
as Shamseer and Vohra suggest, it seems possible that
vitamin C might have a greater effect on the common
cold and other respiratory infections (31) in developing
countries in which low dietary vitamin C intake and
high burden of respiratory infections coexist.
Harri Hemil¨
Renske Bax, Leo Spee and Marieke
Madderom’s Commentary
The common cold is an acute, self-limiting, innocent
but frequent viral infection of the upper respiratory
tract. A variety of agents, ranging from anecdotal folk
Copyright 2008 John Wiley & Sons, Ltd. Evid.-Based Child Health 3: 723 –728 (2008)
DOI: 10.1002/ebch.261
726 L. Shamseer, S. Vohra, R. Bax, L. Spee, M. Madderom and H. Hemil¨
remedies to extensively studied medications have been
suggested as therapy. Ascorbic acid (vitamin C) is
one of these possible agents. However, its role in
preventing and treating the common cold has been
controversial for many years. Public interest is high,
and vitamin C continues to be widely used as a
preventive and therapeutic agent for this condition.
Infants and children have more colds and experience
more prolonged symptoms compared to adults so
might be a group that can benefit from the use of
vitamin C.
Douglas RM et al. (1) systematically reviewed all
published trials regarding vitamin C as a prophylac-
tic or as a therapeutic agent on the incidence, the
duration and the severity of the common cold. The
authors concluded that the prophylactic supplementa-
tion of vitamin C did not reduce the incidence of the
common cold in studies including a mixed population
of adults and children. The therapeutic trials provided
inconsistent evidence for an effect of vitamin C on the
severity and duration of the common cold.
The meta-analysis in prophylactic studies on dura-
tion of common colds was divided into two subgroups:
adults and children. Regarding children, this was the
only outcome reported. All of the participating chil-
dren were of school age. The authors found an 8%
reduction in common cold duration within the adult
participants and a 13.6% reduction within the child
The aforementioned reduction in the duration of
common colds within children was based on 12
prophylactic comparison trials, which include 2,434
episodes of illness. In these trials the dosage of
vitamin C varied from 0.2 g to 2.0 g. The pooled
effect of 13.6% reduction had a 95% CI 5.621.6%.
The authors estimated this would result in an average
reduction of symptomatic days from about 28 days to
24 days per year per child.
In order to be able to comment on the clinical rel-
evance of these findings we would like to highlight
some questions that arise after reading this careful
review. The authors found a reduction in the duration
of common cold when using vitamin C as a pro-
phylaxis, but did not comment on the compliance of
the participating children. Low compliance may have
underestimated the effect of vitamin C.
Furthermore, we question the dosages used in the
different trials. Adults and children were taking the
same dosage of vitamin C. Optimal dosages for
children were not studied and we wonder if the
differences in dosage for weight could explain the
difference in outcome between adults and children. In
addition, we wonder if the effect of vitamin C would
increase with higher dosages without increasing the
risk of adverse events.
The prophylactic trials included in the review varied
in study period from 2 weeks to 9 months. We con-
sider the duration of these studies too short to get a
reliable estimate of reduction in duration of common
colds throughout the year, especially because informa-
tion on the season in which studies were performed
was lacking. In addition, generalizability of the study
results is questionable because there is no information
on the geographic locations of the trials and social eco-
nomic background or nutritional state of the children,
all factors that might be of influence on the results.
Because it is doubtful whether a reduction of 4 days
of common cold throughout a year will increase the
child’s well being, the real beneficial effect of vitamin
C prophylaxis in children might well be the reduction
in sick leave for the parents. This effect has economic
consequences and should be weighted against the costs
of taking vitamin C. In order to make a balance
between costs and benefit, information on the duration
of medication intake is needed. Unfortunately, this
information was not presented. Therefore, questions
important for clinical decision making, such as: ‘how
long do you have to take prophylactic vitamin C to
achieve an effect?’ cannot be answered.
As for now, given the small clinical relevance of the
reduction in duration of an innocent ailment we do not
recommend vitamin C as a prophylaxis for common
cold in children. Compliance, optimal dosage and
duration of intake need clarification before important
questions about the cost effectiveness of vitamin C
intake in children can be answered. In the mean time,
we would like to advise parents, recognizing the kiwi
as a rich vitamin C source, to take heed to an adapted
old saying: ‘A kiwi a day keeps the doctor away’.
Declaration of Interest
Response from the review author to the
commentary by Bax, Spee and Madderom
I agree with Bax et al.’s proposal that the dose
per weight may be a fundamentally important vari-
able when considering the effect of vitamin C on
colds. However, each scientific report is a compro-
mise between the length and details, and our Cochrane
review is already long for an average reader (1). Not
all specifics could be discussed, yet the dose-response
question was briefly commented on, with the reader
being guided to a separate systematic review (32).
In 1999, I divided the vitamin C common cold
trials simultaneously by dose: 1 g/day vs. 2 g/day
regularly over the trial, and by participants: children
vs. adults (32). A major challenge in the analysis
was choosing an appropriate outcome. Essentially all
trials report the duration of common cold symptoms.
However, for the patient and the society, the days off
work or school or the subjective severity may be much
more relevant outcomes than the length of time for
which the nose is running. Vitamin C might have a
different effect on different outcomes. For example,
Copyright 2008 John Wiley & Sons, Ltd. Evid.-Based Child Health 3: 723 –728 (2008)
DOI: 10.1002/ebch.261
Commentaries on ‘Vitamin C for Preventing and Treating the Common Cold’ 727
with 615 Swedish schoolchildren, Ludvigsson et al.
(27) found that 1 g/day vitamin C shortened the
symptoms of upper respiratory tract infection (URI)
by just 6% (P =0.5), but the absence from school
because of URI was reduced by 14% (P =0.016).
In the 1999 analysis, when several outcomes were
published in a trial report, I selected the outcomes
seemingly most important for the patient, such as days
off work or school (32), which made the outcomes
more relevant but more heterogeneous. In five trials
with adults who were administered 1 g/day of vitamin
C, the mean decrease in cold duration was only
7%, whereas in two trials with children administered
2 g/day the mean decrease was four times higher, 26%
(32–34). Children administered 1 g/day and adults
administered 2 g/day were in the middle with mean
effects of 13% and 20%, respectively. The pattern
of results supports dose dependency, given also the
lower average weight of children (32). Nevertheless,
the conclusions must be cautious, because the outcome
is heterogeneous.
One trial with children tested different vitamin C
doses for separate groups using the same outcome
definition (33). Compared with the placebo group,
colds were 12% shorter in children administered
1 g/day of vitamin C and 29% shorter in those
administered 2 g/day (33); however, the groups were
small and children given the higher dose were older.
The most crucial trial that tested dose-dependency
administered 3 and 6 g/day of vitamin C to adults
randomized to four groups (35); the higher dose caused
twice the effect of the lower dose (25, 32, 35, 36).
So far, there is no definite evidence to claim dose-
dependency in the region of high doses, but the
described trends are consistent with such a conception.
Bax et al. suggest that low compliance might have
been a problem in trials with children. In fact, there is
empirical evidence to support their proposal. During
the trial, vitamin C levels increased in the plasma of
older children (33) and in the urine of schoolboys
(37) given a placebo, suggesting that tablets were
exchanged by playful children. The trial by Carr et al.
(38) with twins aged 14 to 64 years (mean 25 y) is
also interesting inasmuch as a significant reduction in
common cold duration was observed in twins living
apart (35%, P <0.01), but no effect was seen in
twins living together (0%), who probably swapped
their tablets to a great extent - not so easy for twins
living apart. Thus, in some trials with children the
mischief of the subjects may have confounded the
results and the observed difference may underestimate
the true physiological effect.
Bax et al. claim that in our Cochrane review “there
is no information on the geographic locations of the
trials.” However, our table “Characteristics of included
studies” describes for each included trial the country
in which the trial was carried out (1).
Although Bax et al.’s advice to give children kiwi
as a source of vitamin C is a pleasant ending to their
commentary, evidence and consideration of cost effec-
tiveness should be required for such an advice, too.
One gram of vitamin C cost pennies, but corresponds
to some half kilograms of kiwi (about 200 mg vita-
min C/100 g fruit) which has a substantially higher
cost. Thus, if we assume that vitamin C is the impor-
tant substance in the kiwi fruit, it is much more
cost effective to use pure vitamin C. Moreover, if
we assume that it is not vitamin C that is beneficial
in kiwi, then we should require evidence indicating
that kiwi in general is effective for some health out-
Based on our Cochrane review, regular vitamin
C supplementation to prevent the common cold in
ordinary children and adults should be discouraged.
On the other hand, given the evidence that vitamin C
reduces the incidence of colds in children and adults
under heavy acute physical stress, it seems reasonable
to test the effect of vitamin C at an individual level for
children who exercise heavily and have a concomitant
problem of frequent respiratory infections.
The consistent effect of regular vitamin C supple-
mentation on the duration and severity of colds indi-
cates a biological effect. With such an effect on com-
mon cold symptoms, it would appear reasonable to
administer vitamin C therapeutically, starting immedi-
ately after the first symptoms; however, no therapeutic
trials have been carried out in children (1,32). The lack
of therapeutic trials with children may justify a con-
clusion that vitamin C should not be recommended for
treating colds in children, because there is no direct
evidence of benefit.
On the other hand, there is indirect justification to
test vitamin C for treating colds in children. Two
trials with children administered 2 g/day vitamin C
regularly, and they found a 26% reduction in common
cold duration (3234). A single trial has compared the
effect of regular and therapeutic (5 days during colds)
vitamin C supplementation (3 g/day) on common cold
duration (35). There was no evidence that the 5-day
therapeutic supplementation would be less effective
than regular supplementation (36). Consequently, the
26% effect on children given 2 g/day vitamin C
regularly may serve as a crude estimate for the
benefit of a similar therapeutic dosage for children.
Furthermore, the result of a controlled trial is always
an average for a group. Accordingly, vitamin C
is much more (and much less) effective for some
individual people than suggested by a single trial,
or by the pooled results of a meta-analysis. Thus,
there seems to be a justification to test therapeutic
vitamin C at the individual level for children who
have problems with respiratory infections, because
there is strong evidence that vitamin C differs from
placebo, it is inexpensive and safe and, unlike the
antibiotics (39), it does not cause harms on microbial
Harri Hemil¨
Copyright 2008 John Wiley & Sons, Ltd. Evid.-Based Child Health 3: 723 –728 (2008)
DOI: 10.1002/ebch.261
728 L. Shamseer, S. Vohra, R. Bax, L. Spee, M. Madderom and H. Hemil¨
1. Douglas RM, Hemil¨
a H, Chalker E, Treacy B. Vitamin C for
preventing and treating the common cold. Cochrane Database
of Systematic Reviews 2007, Issue 3. Art. No.: CD000980. DOI:
2. McElroy BH, Miller SP. Effectiveness of zinc gluconate glycine
lozenges (Cold-Eeze) against the common cold in school-aged
subjects: a retrospective chart review. Am J Ther. 2002; 9(6):
472– 475.
3. Natural Health Product Directorate. Natural Health Product
Regulations. 2004; Available at:
mps/prodnatur/about-apropos/glance-apercu e.html. Accessed May
13, 2008.
4. Bhasale A, Lissiman E. Garlic for the Common Cold. (Protocol).
Cochrane Database of Systematic Reviews 2006 Issue 4. Art. No.:
5. Linde K, Barrett B, W¨
olkart K, Bauer R, Melchart D. Echinacea
for preventing and treating the common cold. Cochrane Database
of Systematic Reviews 2006, Issue 3. Art. No.: CD000530.
6. Marshall I. Zinc for the common cold. Cochrane Database of
Systematic Reviews 2006 Issue 3. Art. No.: CD001364.
7. Wu T, Zhang J, Qiu Y, Xie L, Liu GJ. Chinese medicinal herbs
for the common cold. Cochrane Database of Systematic Reviews
2007, Issue 1. Art. No.: CD004782.
8. Jadad AR, Moore RA, Carroll D, Jenkinson C, Reynolds DJM,
Gavaghan DJ, et al. Assessing the quality of reports of randomized
clinical trials: is blinding necessary? Controlled Clin Trials. 1996;
17(1): 1– 12.
9. Dickersin K. The existence of publication bias and risk factors for
its occurrence. JAMA. 1990; 263(10): 1385–1389.
10. Pittler MH, Abbot NC, Harkness EF, Ernst E. Location bias in
controlled clinical trials of complementary/alternative therapies.
J Clin Epidemiol. 2000; 53(5): 485 489.
11. Ernst E, Pittler MH. Re-analysis of previous meta-analysis of
clinical trials of homeopathy. J Clin Epidemiol. 2000; 53(11):
12. Caufield T, DeBow S. A systematic review of how homeopathy
is represented in conventional and CAM peer reviewed journals.
BMC Complement Alternat Med. 1999; 5(12).
13. Bloom BS, Retbi A, Dahan S, Jonsson E. Evaluation of random-
ized controlled trials on complementary and alternative medicine.
Int J Technol Assess Health Care. 2000; 16(1): 13– 21.
14. Sampson M, Campbell K, Ajiferuke I, Moher D. Randomized
controlled trials in pediatric complementary and alternative
medicine: where can they be found? BMC Pediatrics. 2003; 3(1).
15. Center for Disease Control and Prevention. Nonspecific Upper
Respiratory Tract Infection. 2006; Available at:
germstopper/materials/home work school.pdf. Accessed May 9,
16. National Institutes of Health. National Institute of Allergy
and infectious disease. NIAID Health & Science Topic:
Common Cold. 2007; Available at:
healthscience/healthtopics/colds. Accessed May 2005, 2007.
17. Goldman RD, Rogovik AL. Complementary and Alternative
Medicine use for Children – do we know enough? BMC
Complement Alternat Med. 2005; 82(2): 131 134.
18. Wilson K, Busse JW, Gilchrist A, Vohra S, Boon H, Mills E.
Characteristics of pediatric and adolescent patients attending a
naturopathic college clinic in Canada. Pediatrics. 2005; 115(3):
19. Drug Therapy and Hazardous Substances Committee. Children and
natural health products: What a clinician should know. Paediatr
Child Health. 2005; 10(4): 227 –232.
20. Chalmers TC. Effects of ascorbic acid on the common cold: an
evaluation of the evidence. Am J Med. 1975; 58: 532 –536.
21. Hemil¨
a H, Herman ZS. Vitamin C and the common cold: a
retrospective analysis of Chalmers’ review. J Am Coll Nutr. 1995;
14: 116– 123.
22. Hemil¨
a H. Do vitamins C and E affect respiratory infections? [PhD
Thesis]. Helsinki, Finland: University of Helsinki, 2006; 36– 38.
Available at:
(see also:
23. Kleijnen J, Riet G, Knipschild PG. Vitamin C and the common
cold; a review of the megadose literature [in Dutch]. Ned Tijdschr
Geneeskd. 1989; 133: 1532– 1535.
24. Kleijnen J, Knipschild P. The comprehensiveness of Medline and
Embase computer searches. Pharm Weekbl Sci Ed. 1992; 14:
316– 320.
25. Hemil¨
a H. Do vitamins C and E affect respiratory infections? [PhD
Thesis]. Helsinki, Finland: University of Helsinki, 2006; 20–27
and 38– 40.
26. Lau J, Ioannidis JPA, Terrin N, Schmid CH, Olkin I. The case of
the misleading funnel plot. BMJ. 2006; 333: 597 –600.
27. Ludvigsson J, Hansson LO, Tibbling G. Vitamin C as a preventive
medicine against common colds in children. Scand J Infect Dis.
1977; 9: 91– 98.
28. Ritzel G. Critical analysis of the role of vitamin C in the
prophylaxis and treatment of the common cold [in German]. Helv
Med Acta. 1961; 28: 63–68 (English translation available at:
29. Hemil¨
a H. Vitamin C intake and susceptibility to the common cold.
Br J Nutr. 1997; 77: 59 72. Discussion in: 1997; 78: 857–866.
30. Anderson TW, Reid DBW, Beaton GH. Vitamin C and the
common cold: a double-blind trial. Can Med Assoc J. 1972; 107:
503– 508. Erratum in: 1973; 108: 133.
31. Hemil¨
a H, Louhiala P. Vitamin C may affect lung infections. JR
Soc Med. 2007; 100: 495 –498.
32. Hemil¨
a H. Vitamin C supplementation and common cold
symptoms: factors affecting the magnitude of the benefit. Med
Hypotheses 1999; 52: 171– 178.
33. Coulehan JL, Reisinger KS, Rogers KD, Bradley DW. Vitamin C
prophylaxis in a boarding school. N Engl J Med 1974; 290: 6–10.
34. Bancalari A, Seguel C, Neira F, Ruiz I, Calvo, C. Prophylactic
value of vitamin C in acute respiratory infections of schoolchildren
[in Spanish]. Rev Med Chile 1984; 112: 871 876. (English transla-
tion available at:
35. Karlowski TR, Chalmers TC, Frenkel LD, Kapikian AZ, Lewis TL,
Lynch JM. Ascorbic acid for the common cold: a prophylactic and
therapeutic trial. JAMA 1975; 231: 1038–1042.
36. Hemil¨
a H. Vitamin C, the placebo effect, and the common cold: a
case study of how preconceptions influence the analysis of results.
J Clin Epidemiol 1996; 49: 1079 1084. Discussion in: 1996; 49:
1085– 1087.
37. Miller JZ, Nance WE, Norton JA, Wolen RL, Griffith RS, Rose RJ.
Therapeutic effect of vitamin C: a co-twin control study. JAMA
1977; 237: 248– 251.
38. Carr AB, Einstein R, Lai LYC, Martin NG, Starmer GA. Vitamin
C and the common cold: a second MZ cotwin control study. Acta
Genet Med Gemellol 1981; 30: 249 –255.
39. Gonzales R, Sande M. What will it take to stop physicians from
prescribing antibiotics in acute bronchitis? Lancet 1995; 345:
665– 666.
Copyright 2008 John Wiley & Sons, Ltd. Evid.-Based Child Health 3: 723 –728 (2008)
DOI: 10.1002/ebch.261
... Enhanced outbreak and severity of pneumonia and different infections [40,41]. Reduced resistance to infection and cancer, Reduced delayed-type hypersensitivity reaction, impaired wound healing and concerning its supplement, antioxidant attributes defend leukocytes and lymphocytes from oxidative stress [42] For elderly people possible reduction in an incidence and period of pneumonia [41] For Children: reduced period and severity of respiratory disease signs [43]; amended outcomes in pneumonia, malaria, and diarrhoeic symptoms. As a result, Increased the risk of all types of infection (bacterial, viral, and fungal), however particularly diarrhea and pneumonia [44]. ...
... When less vitamin C situation, conjointly, will increase susceptibleness to infections like pneumonia [45], in all probability, as a result of low levels of antioxidants like vitamin C, could not counteract the oxidative stress distinctive in pneumonia [40]. Enhanced production of ROS throughout the immune reaction to pathogens would possibly reduce vitamin C levels extra [43]. The lack of Vitamin D also increases the risk of infection and autoimmune diseases like multiple sclerosis and diabetes by the activity of vitamin D receptors [46,47]. ...
... Vitamin C supplements lead to reduces the period and severity of common cold signs in adults [43]. When you are in those beneath physical stress (e.g., at work, throughout sports, and under extreme temperatures) [40] or in cases wherever levels of vitamin C are somewhat below suggested levels, vitamin C supplements lead to reduce respiratory disease occurrence. ...
Full-text available
Coronaviruses belong to the order Nidovirales and have families such as Coronaviridae, Arteriviridae, and Roniviridae. Coronavirida has two subfamilies named Coronavirinae and Torovirinae. Alpha, beta, gamma, and delta are also four groups of the Coronavirinae subfamily. All viruses belonging to the order Nidovirales are coated and positive-sense single-stranded RNA with a viral genome length of 27 to 34 kilobases. The particles are composed of 20-nm-diameter polymers that resemble a solar corona or a royal corona in the view of electron microscopy, which is why members of the family have named it Coronavirus. In this review article, we briefly describe coronaviruses, how they spread, the pathogenicity, current prevention and treatment strategies, and the association and effect of food with the virus.
... In a metaanalysis of 29 controlled trials with 11,306 participants, it was shown that regular intake of about 1 g of vitamin C per day did not prevent upper respiratory tract infection (URTI). However, the same experiments showed that vitamin C shortened and reduced URTIs (reducing the duration of infection by 8% in adults and 14% in children) during the course of vitamin C administration [45]. Based on the above results, and given that COVID-19 is often much more severe than normal URTIs, and while COVID-19 is highly prevalent, a regular increase in daily vitamin C intake may be justifiable. ...
Full-text available
The COVID-19 pandemic, which causes severe respiratory tract infections in humans, has become a global health concern and is spreading rapidly. At present, the most important issue associated with COVID-19 is the immune system and the factors that affect it. It is well known that cow’s milk is highly rich in micronutrients that increase and strengthen the immune system. Research shows that the administration of these nutrients is very effective in fighting COVID-19, and a deficiency in any of them can be a weakness in the fight against the virus. On the other hand, cow’s milk is accessible to the whole population, and drinking colostrum, raw, and micro-filtered milk from cows vaccinated against SARS-CoV-2 could provide individuals with short-term protection against the SARS-CoV-2 infection until vaccines become commercially available. This review aimed to discuss the effects of milk vitamins, minerals, and bioactive peptides on general health in humans to combat viral diseases, especially COVID-19, and to what extent cow’s milk consumption plays a role in providing these metabolites. Cow’s milk contains many bioactive compounds that include vitamins, minerals, biogenic amines, nucleotides, oligosaccharides, organic acids, and immunoglobulins. Humans can meet a significant portion of their requirements for vitamins and minerals through the consumption of cow’s milk. Recent studies have shown that micronutrients such as vitamins D, E, B, C, and A as well as minerals Zn, Cu, Mg, I, and Se and bioactive peptides, each can have positive and significant effects on strengthening the immune system and general health in humans.
... A meta-analysis that included 29 trials and 11,306 participants found that taking vitamin C regularly did not have an impact on cold incidence. Within this review, a comparison of 31 studies that included 9745 common cold episodes determined use of vitamin C in colds was associated with reducing cold duration by 8% in adults and by 14% in children 79 . Based on published trials reviewed, this meta-analysis did not conclusively show that routine use of vitamin C in therapeutic trials was effective; however, more research is warranted based on findings from regular supplementation trials demonstrating effectiveness. ...
Full-text available
In the Hubei region of China, a pneumonia outbreak occurred in December 2019, which was confirmed to be caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). It quickly became known as Coronavirus Disease 2019 or simply COVID-19, a pandemic that continues to devastate countries across the world. Through this COVID-19 pandemic, pharmacists across the globe have continued to offer direct patient care and provided frontline service to society. However, while the frontline staff is heralded, they are relegated to the background and overlooked most of the time. The most reachable healthcare providers are pharmacists because they can provide direct medical services despite tight regulations and restrictions related to the pandemic. During this pandemic, the involvement of pharmacists to handle COVID-19 and its complications proved to be crucial in alleviating the burden on the already strained healthcare system. They have provided very important services such as distributing medications to patients, encouraging adherence to medications for better control of chronic diseases, consulting on minor illnesses, clarifying myths regarding COVID-19, and contributing to COVID-19 screening. The treatment or management of COVID-19 was based on initial findings but is now being updated several times based on viral mutation, different studies across the globe, etc. This review focuses on recent clinical updates and tools that would help pharmacists with a more systematic approach to properly handling COVID-19 and its complications.
... Moreover, foods containing 200 mg or more vitamin C may be labeled with an additional health claim: 'Vitamin C contributes to maintain the normal function of the immune system during and after intense physical exercise' [40]. The evidence for vitamin C's additional health claim comes from three systematic reviews examining the role of vitamin C supplementation in the prevention, severity, and treatment of the common cold [41][42][43]. The results of the reviews showed that there is some evidence suggesting that individuals who are exposed to short periods of vigorous exercise and/or cold environments benefit from regular vitamin C intake above 200 mg/day based on the duration and severity of the common cold [40]. ...
Full-text available
The importance of a well-functioning and balanced immune system has become more apparent in recent decades. Various elements have however not yet been uncovered as shown, for example, in the uncertainty on immune system responses to COVID-19. Fungal beta-glucans are bioactive molecules with immunomodulating properties. Insights into the effects and function of beta-glucans, which have been used in traditional Chinese medicine for centuries, advances with the help of modern immunological and biotechnological methods. However, it is still unclear into which area beta-glucans fit best: supplements or medicine? This review has highlighted the potential application of fungal beta-glucans in nutrition and medicine, reviewing their formulation, efficacy, safety profile, and immunomodulating effects. The current status of dietary fungal glucans with respect to the European scientific requirements for health claims related to the immune system and defense against pathogens has been reviewed. Comparing the evidence base of the putative health effects of fungal beta-glucan supplements with the published guidance documents by EFSA on substantiating immune stimulation and pathogen defense by food products shows that fungal beta-glucans could play a role in supporting and maintaining health and, thus, can be seen as a good health-promoting substance from food, which could mean that this effect may also be claimed if approved. In addition to these developments related to food uses of beta-glucan-containing supplements, beta-glucans could also hold a novel position in Western medicine as the concept of trained immunity is relatively new and has not been investigated to a large extent. These innovative concepts, together with the emerging success of modern immunological and biotechnological methods, suggest that fungal glucans may play a promising role in both perspectives, and that there are possibilities for traditional medicine to provide an immunological application in both medicine and nutrition.
... And despite the available standards of orthodox management and treatment of diarrhea, a high number of people in developing countries depend on herbs for the management and treatment of diarrhea (Umer et al., 2013).Currently the used medications in diarrhea treatment are essential in the management of diarrhea, but however, they are Vitamin C is a powerful antioxidant vitamin and its role played in various toxicity conditions in the body cannot be overemphasized because of its ability to scavenge free radicals that promotes toxicity (Danbatureet al., 2015). Several investigations have been carried out on physiological benefits of ascorbic acid and its application as therapeutic agents in various disease states (Hemila & Chalker, 2013). ...
... /2020 Vitamin C is a powerful antioxidant vitamin and its role played in various toxicity conditions in the body cannot be overemphasized because of its ability to scavenge free radicals that promotes toxicity (Danbature et al., 2015). Several investigations have been carried out on physiological benefits of ascorbic acid and its application as therapeutic agents in various disease states (Hemila & Chalker, 2013). ...
Full-text available
Background Diarrhea is distinguished by prevalence of bowel movement accompanied by a loose consistency of stools, resulting from hyper peristalsis of the small intestine or colon, Diarrhea is a major challenge among infants and growing children. The study was carried out to assess the result of combined treatment of vitamin C and loperamide on intestinal Na ⁺ , K ⁺ - ATPase, alkaline phosphatase, and lipid peroxidation in castor oil induced diarrheal wistar rats. Method A total of 18 wistar rats weighing 180-200g were randomly divided into 6 groups, (Group 1 Normal control no castor oil, no treatment administered, Group 2 Experimental control were given castor oil 3.0 ml/kg body weight with no treatment, Group 3 Standard control were given castor oil 3.0 ml/kg body weight + loperamide, Group 4 Treatment 1 were administered 3.0 ml/kg body weight + 25 mg/kg combined effect of vitamin C and loperamide, Group 5 Treatment 2 were administered 3.0 ml/kg body weight + 50 mg/kg combined effect of vitamin C and loperamide, and Group 6 were administered 3.0 ml/kg body weight + 100 mg/kg combined effect of vitamin C and loperamide) with 3 rats per group; the experiment lasted for 24 hours. The action of intestinal alkaline phosphatase, Na ⁺ , K ⁺ - ATPase and malondialdehyde were determined. Result Descriptive statistical analysis was adopted using SPSS version 20. Combined effect of vitamin C and loperamide significantly (p<0.05) lowered the elevated levels of malondialdehyde caused by castor oil induced diarrhea; the Na ⁺ , K ⁺ - ATPase intestinal activity treatment with both vitamin C and loperamide significantly elevated the activity of Na ⁺ , K ⁺ ATPase when compared with the normal control, but both treatments (loperamide alone and vitamin C plus loperamide were not significantly different (p<0.05) to themselves. However, at 50 mg/kg body weight of combined effect of vitamin C and loperamide it showed significant difference in the action of intestinal alkaline phosphatase. Conclusion Findings of this study therefore, indicate that a combined effect of loperamide and vitamin C will be an effective therapeutic agent in the management of diarrhea by scavenging of free radicals generated in the cause of diarrheal to reduce lipid peroxidation. Therefore, combined effect of vitamin C and loperamide should be encouraged in the management of diarrhea. Further research should be directed towards assessing the therapeutic action of vitamin C only in the management of diarrhea.
... In several experimental settings vitamin C has proved to increase the functioning of phagocytes, proliferation of T lymphocytes and production of interferon and also plays important role in virus replication. Several controlled trials have proved vitamin C to be effective in improving endothelial functions [30][31] , lowering blood pressure [32] , decreasing blood glucose level in type 2 diabetes [33] , decreasing broncho-constrictions [34,35] and prevention from cold [35][36][37][38] . A number of researchers have suggested that vitamin C in high doses is directly virucidal [39][40][41][42] . ...
... Konuya ilişkin olarak C vitamininin üst solunum yolu enfeksiyonları üzerine etkisinin araştırıldığı 29 çalışma ve 11306 bireyin dâhil edildiği bir Cochrane derlemesinde, ortalama 1 g/gün C vitamini alımının üst solunum yolu enfeksiyonunu önlemediği belirlenmiştir. Ancak üst solunum yolu enfeksiyonu süresini yetişkinlerde ortalama %8, çocuklarda %14 kısalttığı bildirilmiştir (Hemilä & Chalker, 2013). ...
Full-text available
Pandemi olarak kabul edilen koronavirüs hastalığı 2019 (COVID-19) ülkelerin sağlık sistemleri ve ekonomileri için önemli bir tehdit haline gelmiştir. Güncel durumda, bu virüs salgınını kesin olarak önleyebilen veya tedavi edebilen herhangi bir ilaç bulunmamaktadır. Bu nedenle, hastalıktan korunmak ve hastalığı yönetmek için sağlıklı bir bağışıklık sistemine sahip olmak önemlidir. Vitamin ve mineraller, sağlıklı bir bağışıklık yanıtının oluşturulmasında etkin rol oynayan ve vücudun enfeksiyonlara karşı olan direncini arttıran önemli besin ögeleridir. Vitamin ve minerallerin, makrofajlar, nötrofiller ve doğal öldürücü hücrelerin gelişiminin ve farklılaşmasının sağlanması, T ve B lenfosit yanıtının düzenlenmesi gibi bağışıklık sistemi üzerinde çeşitli etkileri mevcuttur. COVID-19 pandemisinde bu vitamin ve mineraller hem literatürde hem de medyada yaygın olarak tartışılmaya başlanmıştır. Bu nedenle, bu derlemede COVID-19 odağında viral enfeksiyonlarda vitamin ve minerallerin rolü incelenmiştir.
Full-text available
Background: COVID-19 is a pandemic infectious disease caused by the Corona virus, has become a major global threat. The coronavirus mainly targets the human respiratory system. Cytokine storm and other altered immune responses have been shown to be associated with pathogenesis of diseases. The immune and the digestive systems both have been shared the important functions in terms of nutrients acquisition and host defense as gut microbiota. The main purpose of this study was to state the importance of healthy nutrition to boost immunity and its effect on the prevention and treatment of COVID-19. Materials and methods: In this review study, articles were collected by searching databases including PubMed, Google Scholar, Science Direct and Scopus using the keywords COVID-19 pandemic, Immunity system, Nutrients, and Nutritional supplement. Based on the inclusion and exclusion criteria, 82 qualified articles related to the subjected were evaluated. Results: Micronutrients and macronutrients such as vitamins as well as other elements such as zinc, iron, selenium, and copper, proteins, and omega-3 long chain fatty acid play an important role in strengthening the immune system and increasing resistance to respiratory infections such as COVID-19. Conclusion: A healthy diet to maintenance the host macro- and micronutrient and probiotics in food can be an effective and promising agent for the prevention and treatment of COVID-19 disease.
Preparations of the plant Echinacea (familiy Compositae) are widely used in some European countries and in North America for common colds. Most consumers and physicians are not aware that products available under the term Echinacea differ appreciably in their composition, mainly due to the use of variable plant material, extraction methods and addition of other components. Now we assessed whether there is evidence that Echinacea preparations are 1) more effective than no treatment; 2) more effective than placebo; 3) similarly effective to other treatments in A) the prevention and B) the treatment of the common cold. Outcomes of interest in prevention trials were: number of individuals with one or more colds, and severity and duration of colds; and in treatment trials: total symptom scores, nasal symptoms and duration of colds. Sixteen trials including a total of 22 comparisons of an Echinacea preparation and a control group met the inclusion criteria. The majority had reasonable to good methodological quality. A variety of different Echinacea preparations were used. None of the three comparisons in the prevention trials showed an effect over placebo. Comparing an Echinacea preparation with placebo as treatment, a significant effect was reported in nine comparisons, a trend in one, and no difference in six. More than one trial was available only for preparations based on the aerial parts from Echinacea purpurea. Therefore we concluded that preparations based on aerial parts of E. purpurea might be effective for the early treatment of colds in adults but results are not fully consistent. Beneficial effects of other Echinacea preparations and for preventative purposes might exist but have not been shown in independently replicated, rigorous randomized trials. [1,2] Again a recent meta-analysis reported that standardized extracts of Echinacea were effective in the prevention of symptoms of the common cold after clinical inoculation, compared with placebo. [3] References: [1] Linde K., Barrett B. et al. (2006) The Cochrane Database of Systematic Reviews Issue 1. [2] Gillespie E.L., Coleman C.I. (2006) Conn. Med. 70: 93–97. [3] Schoop R., Klein P. et al. (2006) Clin. Ther. 28: 174–183.
A prospective, randomized, double-blind study was carried out to determine whether vitamin C prophylaxis, 2.0 g/day, vs placebo prophylaxis would reduce the incidence or morbidity of the common cold and other respiratory illnesses in 674 marine recruits during an eight-week period. Whole-blood ascorbic acid levels measured six weeks after initiation of the study were significantly higher in the vitamin C group. There was no difference between the two groups in the incidence or duration of colds. The vitamin C group rated their colds as being less severe, but this was not reflected in different symptom complexes or in fewer sick-call visits or training days lost. This study and the literature do not support the prophylactic use of vitamin C to prevent the common cold. (JAMA 241:908-911, 1979)
Objectives: Use of complementary and alternative medicine (CAM) is growing in all Western countries. The goal of this study was to evaluate quality of randomized controlled trials (RCTs) of CAM interventions for specific diagnoses to inform clinical decision making. Methods: MEDLINE and related databases were searched for CAM RCTs. Visual review was done of bibliographies, meta-analyses, and CAM journals. Inclusion criteria for review and scoring were blinded RCT, specified diagnosis and intervention, complete study published between January 1, 1966 and July 31, 1998 in an English-language, peer-reviewed journal. Two reviewers independently scored each study. Results: More than 5,000 trials were found, but only 258 met all study inclusion criteria. The main cause for rejection (> 90%) was that the study was not an RCT or had no blinding. Mean score across 95 diagnosis/intervention categories was 44.7 (S.D. +/- 14.3) on a 100-point scale. Ordinary least-squares regression found date of publication, biostatistician as author or consultant, published in one of five widely read English-language medical journals and diagnosis/intervention category of hypertension/relaxation as significant predictors of higher scores. Conclusions: The overall quality of evidence for CAM RCTs is poor but improving slowly over time, about the same as that of biomedicine. Thus, most services are provided without good evidence of benefit.