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Immune-Enhancing Role of Vitamin C and Zinc and Effect on Clinical Conditions

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Abstract

Vitamin C concentrations in the plasma and leukocytes rapidly decline during infections and stress. Supplementation of vitamin C was found to improve components of the human immune system such as antimicrobial and natural killer cell activities, lymphocyte proliferation, chemotaxis, and delayed-type hypersensitivity. Vitamin C contributes to maintaining the redox integrity of cells and thereby protects them against reactive oxygen species generated during the respiratory burst and in the inflammatory response. Likewise, zinc undernutrition or deficiency was shown to impair cellular mediators of innate immunity such as phagocytosis, natural killer cell activity, and the generation of oxidative burst. Therefore, both nutrients play important roles in immune function and the modulation of host resistance to infectious agents, reducing the risk, severity, and duration of infectious diseases. This is of special importance in populations in which insufficient intake of these nutrients is prevalent. In the developing world, this is the case in low- and middle-income countries, but also in subpopulations in industrialized countries, e.g. in the elderly. A large number of randomized controlled intervention trials with intakes of up to 1 g of vitamin C and up to 30 mg of zinc are available. These trials document that adequate intakes of vitamin C and zinc ameliorate symptoms and shorten the duration of respiratory tract infections including the common cold. Furthermore, vitamin C and zinc reduce the incidence and improve the outcome of pneumonia, malaria, and diarrhea infections, especially in children in developing countries.
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Review
Ann Nutr Metab 2006;50:85–94
DOI: 10.1159/000090495
Immune-Enhancing Role of Vitamin C
and Zinc and Effect on Clinical Conditions
Eva S. Wintergerst
a
Silvia Maggini
a
Dietrich H. Hornig
b
a
Bayer Consumer Care Ltd., Basel , and
b
Reinach , Switzerland
quate intakes of vitamin C and zinc ameliorate symptoms
and shorten the duration of respiratory tract infections
including the common cold. Furthermore, vitamin C and
zinc reduce the incidence and improve the outcome of
pneumonia, malaria, and diarrhea infections, especially
in children in developing countries.
Copyright © 2006 S. Karger AG, Basel
Nutritional and Physiological Aspects of
Vitamin C and Zinc
Vitamin C (ascorbic acid) and zinc are essential nutri-
ents and play important roles in nutrition and mainte-
nance of human health. Both have profound effects on
cellular growth and differentiation, and are vital for the
optimal functioning of the immune system. Inadequacy
and clinical defi ciency of vitamin C and/or zinc lead to
impaired immune response with altered resistance to in-
fections, impaired growth, and weakened collagenous
structures with delayed wound healing.
The nutritional and physiological aspects of these es-
sential nutrients have been widely reviewed and a large
number of comprehensive publications on vitamin C [1,
2] and zinc [3, 4]
are available. Therefore, the nutritional
and physiological aspects of these essential nutrients are
only briefl y summarized here.
Vitamin C has direct antioxidant capacity and con-
tributes to the protection of cells from the damaging ef-
fects of endogenously produced or exogenous reactive
Key Words
Vitamin C Zinc Oxidative stress Effects on immune
response Risk of infections
Abstract
Vitamin C concentrations in the plasma and leukocytes
rapidly decline during infections and stress. Supplemen-
tation of vitamin C was found to improve components of
the human immune system such as antimicrobial and
natural killer cell activities, lymphocyte proliferation,
chemotaxis, and delayed-type hypersensitivity. Vitamin
C contributes to maintaining the redox integrity of cells
and thereby protects them against reactive oxygen spe-
cies generated during the respiratory burst and in the
infl ammatory response. Likewise, zinc undernutrition or
defi ciency was shown to impair cellular mediators of in-
nate immunity such as phagocytosis, natural killer cell
activity, and the generation of oxidative burst. Therefore,
both nutrients play important roles in immune function
and the modulation of host resistance to infectious
agents, reducing the risk, severity, and duration of infec-
tious diseases. This is of special importance in popula-
tions in which insuffi cient intake of these nutrients is
prevalent. In the developing world, this is the case in low-
and middle-income countries, but also in subpopula-
tions in industrialized countries, e.g. in the elderly. A
large number of randomized controlled intervention tri-
als with intakes of up to 1 g of vitamin C and up to 30 mg
of zinc are available. These trials document that ade-
Published online: December 21, 2005
Eva Wintergerst
International Medical Manager, Speciality Vitamins, Bayer Consumer Care Ltd.
Peter-Merian-Strasse 84
CH–4002 Basel (Switzerland)
Tel. +41 58 272 76 72, Fax +41 58 272 76 04, E-Mail eva.wintergerst.ew@bayer.ch
© 2006 S. Karger AG, Basel
0250–6807/06/0502–0085$23.50/0
Accessible online at:
www.karger.com/anm
Wintergerst /Maggini /Hornig
Ann Nutr Metab 2006;50:85–94
86
oxygen radicals and reactive nitrogen species, e.g. during
immune activation. Vitamin C was shown to protect neu-
trophils from reactive oxygen species generated during
phagocytosis [2] , to prevent endogenous oxidative dam-
age to lymphocytes and sperm DNA [5–7] , and vitamin
C supplementation decreased signifi cantly H
2
O
2
-induced
DNA damage in lymphocytes in healthy male and female
nonsmokers [5] . Vitamin C prevents oxidative damage to
lipids, proteins, and DNA, which has been implicated as
a major contributing factor in the development of chron-
ic diseases such as cardiovascular disease, cancer, and
cataract, respectively [2, 8] . Evidence further suggests
that vitamin C provides indirect antioxidant protection
by regenerating other biologically important antioxidants
such as glutathione and vitamin E to their active state [9] .
Vitamin C functions as an electron donor involving either
monooxygenase or dioxygenase activities in a number of
important enzymes: dopamine-
-hydroxylase (biosyn-
thesis of the catecholamines norepinephrine and epi-
nephrine), peptidyl-glycine monooxygenase (amidation
of peptide hormones) and is involved in tyrosine metab-
olism (4-hydroxyphenylpyruvate dioxygensase) [1, 2] . Vi-
tamin C further acts as a cofactor for hydroxylases and
oxygenase metalloenzymes. Proline and lysine hydroxy-
lase catalyze the posttranslational hydroxylation of pep-
tide-bound proline and lysine residues, which is essential
for the development of functionally active collagen in its
triple helical structure and thus for effective wound heal-
ing [10] . Further, it functions as a reducing agent for
mixed-function oxidases, which are of importance in the
drug-metabolizing system in the microsomes, and as a
consequence, in vitamin C defi ciency, the activity of the
drug-metabolizing enzymes and the cytochrome P-450
electron transport are lowered [2] . Ascorbic acid stimu-
lates non-hem iron absorption from the intestine and
modulates iron transport and storage [11] .
Zinc is important in cellular growth and differentia-
tion with profound effects on antioxidant defense, col-
lagen synthesis, and the immune system [3, 4] . A large
number of enzymes depend on zinc for catalytic activity
(e.g. alcohol dehydrogenase; zinc containing metallo-en-
zymes such as RNA polymerases, carbonic anhydrase,
and alkaline phosphatases), and removal of zinc results
in loss of the enzymatic activity without affecting the
enzyme protein irreversibly [12] . By its antioxidant ca-
pacity, zinc contributes to the protection of cells from the
damaging effects of reactive oxygen radicals and reactive
nitrogen species produced during e.g. immune activa-
tion. Zinc antagonizes the catalytic properties of the re-
dox-active metals iron and copper with regard to the for-
mation of hydroxyl radicals from H
2
O
2
and superoxide
by competing with certain types of binding sites for cop-
per and iron, and blocking the initiation of destructive
processes [13] .
Elevated levels of superoxide anions cause increased
formation of reactive oxygen species that can damage lip-
ids, proteins and DNA which has been implicated as a
major contributing factor in chronic diseases such as car-
diovascular disease, cancer and cataract [8] . The antioxi-
dant properties of zinc have recently been reviewed [13] .
The antioxidant enzyme Cu, Zn-superoxide dismutase
catalyzes the reduction of two superoxide anions to mo-
lecular oxygen and hydrogen peroxide. However, in this
enzyme, copper provides the catalytic activity whereas
the role of zinc is structural. Zinc is essential for the in-
tracellular binding of tyrosine kinase to T cell receptors,
which are required for T lymphocyte development and
activation [14, 15] . The mechanism that underlies the
antioxidant action causes acute and chronic effects. The
acute effect may involve protection of protein sulfhydryl
groups against oxidation and oxidative damage to mem-
branes, or reduction in the formation of hydroxyl radicals
from H
2
O
2
through the antagonism of redox-active tran-
sition metals such as copper and iron [16] . Thiol-depen-
dent enzymes and proteins containing thiol groups have
been shown to be protected by zinc from oxidation, e.g.
-aminolevulinate dehydratase, DNA-zinc binding pro-
teins (zinc fi ngers) or tubulin [13] . Studies in zinc-defi -
cient animals and cell systems have shown an increased
free radical production and enhanced injury from expo-
sure to oxidative stress [14] .
Zinc is important for structural integrity by facilitating
protein folding to generate biologically active molecules.
Structural sites or zinc fi ngers have a broad cellular dis-
tribution and are present in transcription and replication
factors, in nuclear hormonal receptors, and in signal
transduction factors. Examples for zinc fi nger transcrip-
tion factors are retinoic acid receptors and vitamin D
receptors. Nuclear hormone receptors include those for
estrogen, testosterone, and vitamin D. Zinc fi nger pro-
teins have a broad cellular distribution and are involved
in protein-protein interaction affecting cellular differen-
tiation and proliferation [17] . Removal of zinc from zinc
nger proteins with apometallothionein in vitro has been
shown for a transcription factor to result in loss of func-
tion [18] . Zinc fi ngers contribute to zinc requirement and
support the fundamental and critical physiological role of
zinc, such as the intracellular binding of tyrosine kinase
to T cell receptors, which are required for T lymphocyte
development and activation [19, 20] .
Potential of Vitamin C and Zinc in
Immune Function
Ann Nutr Metab 2006;50:85–94
87
This overview attempts to demonstrate that suffi cient
intakes of vitamin C and zinc are essential to support ad-
equate immune response, to elaborate on the clinical con-
sequences, such as the risk, severity and duration of infec-
tious diseases, and to demonstrate the relevance of the
immune response modulated by these nutrients to vari-
ous population groups.
Immune Function and Oxidative Stress
The immune system protects the organism from inva-
sion and damage from a wide range of microorganisms,
such as viruses, bacteria, fungi or parasites, by a highly
complex biological response, which involves cellular pro-
liferation, enhanced protein synthesis and infl ammatory
mediator production as well as physiological changes. In
the activation of the immune system, the process of cell
proliferation is most active among T lymphocytes. Con-
currently, protein synthesis, immunoglobulin synthesis
by B lymphocytes, and acute phase protein synthesis in
the liver are enhanced. Infl ammatory mediators such as
the proinfl ammatory cytokines (IL 1; IL 6) and tumor
necrosis factor-
(TNF-
), prostaglandins, leukotrienes,
and reactive oxygen and nitrogen species, are increased
[21] .
The generation of reactive oxygen species is part of the
physiological function of cells involved in host defense,
such as activated neutrophils and macrophages, especial-
ly during chemotactic locomotion and phagocytosis. The
reactive oxygen species play an essential role in the intra-
cellular killing of bacteria and other invading organisms.
Whereas this microbicidal activity is a benefi cial activity,
on the other side the immune system is particularly vul-
nerable to oxidative stress, since immune cells rely on
cell-cell communication via membrane receptors and any
damage to the signaling systems has been shown to impair
the ability to build up an immune response [22, 23] . How-
ever, besides the antimicrobial and therefore protective
properties of these oxidants, other biomolecules may be
vulnerable to free radical attack. Especially, cell mem-
branes rich in long-chain polyunsaturated fatty acids are
susceptible to oxidative destruction, which could lead to
a loss of membrane integrity, altered membrane fl uidity,
and may result in alterations of cell-cell communication,
herewith contributing to degenerative disorders such as
cancer and cardiovascular diseases [8] . Antioxidants,
such as vitamin C and zinc, could play an immunomod-
ulatory role by preventing tissue damage mediated by im-
mune-system-generated reactive oxidant species, espe-
cially in population groups with poor dietary habits. Mar-
ginal or clinical nutrient defi ciency may impair the
proper functioning of the immune system, suppressing
various immune functions, which are critical determi-
nants of host resistance. As a consequence, the defi cient
individual becomes more susceptible to infections. In
many cases, by supplying the defi cient nutrient, immune
function may be normalized and resistance to infections
restored [22, 23] .
Furthermore, vitamin C is involved as an antioxidant
in the maintenance of the endothelial function, mainly
by preventing or reversing endothelial dysfunctions lead-
ing to the development of cardiovascular diseases [24–
26] . Mechanisms discussed include suppression of the
induction of endothelial cell apoptosis [24] , protection of
nitric oxide against oxidative inactivation [26] , stimula-
tion of nitric oxide synthesis [27] , intracellular reduction
of oxidized glutathione [28] , and prevention of the forma-
tion of atherogenic oxidized phospholipids [29] .
Vitamin C and the Immune System
The high cellular concentration of vitamin C and its
rapid decline in plasma and leukocytes during stress and
infection suggest a role in the process of immune response
[30–32] . Vitamin C was found to be a stimulant of leuko-
cyte functions, especially of neutrophil and monocyte
movement. Supplementation of healthy adults (1–3 g/
day) and children (20 mg/kg/day) enhanced neutrophil
chemotaxis in vivo, but bactericidal activity was not en-
hanced [32] . Lymphocyte proliferation was not impaired
in vitamin C defi ciency in humans and the number of
circulating CD4+ or CD8+
cells was not altered [33] . Vi-
tamin C in doses of 1–5 g/day for 3 days and over sev-
eral weeks increased human T lymphocyte proliferation
and neutrophil motility towards lipopolysaccharide-acti-
vated autologous serum [34, 35] . In vitro treatment of
peritoneal macrophages with antioxidant vitamins, in-
cluding vitamin C, was shown to stimulate the entire pro-
cess of phagocytosis. The observed decrease of vitamin C
in plasma and leukocytes during infective periods sug-
gests that the increased generation of oxidizing agents is
counteracted by reaction with vitamin C, and herewith
the host is protected against any harmful oxidative action
[31] .
In studies in healthy subjects, administration of vita-
min C resulted in improvement of several components of
human immune parameters, such as antimicrobial and
natural killer cell activities, lymphocyte proliferation,
Wintergerst /Maggini /Hornig
Ann Nutr Metab 2006;50:85–94
88
chemotaxis, and DTH [35–38] . The effect of vitamin C
intake with the diet on immune function was studied in
young, healthy nonsmokers. The volunteers consumed a
vitamin-C-defi cient diet and then increased their vitamin
C intake from 5 to 250 mg/day. Upon ingestion of the
vitamin-C-defi cient diet, plasma and leukocyte vitamin
C concentrations were decreased by about 50%, and DTH
response to several antigens was decreased as well. With
higher doses (60 and 250 mg/day) the DTH response was
normalized, but lymphocyte proliferation was not affect-
ed [37] . In older people, known to have reduced vitamin
C plasma and leukocyte concentrations even if they are
not institutionalized, vitamin C supplementation result-
ed in enhanced cell-mediated immunity [39] . Intracellu-
lar concentrations of vitamin C in human leukocytes have
been shown to decline with increasing age, accompanied
by neutrophil function impairment. Oral administration
of vitamin C resulted in improved neutrophil functions
and serum immunoglobulin levels [40] . An earlier inves-
tigation showed that administration of 1 g of vitamin C
together with 200 mg of vitamin E for 16 weeks to healthy
elderly women enhanced neutrophil chemotaxis and
phagocytosis, and decreased concentrations in serum lip-
id peroxides, which is indicative of improved resistance
to oxidative stress [41] . Other studies, however, did not
show any alterations in indices of immune function fol-
lowing vitamin C administration, which may be due to
the fact that individuals participating in these studies had
already adequate vitamin C baseline concentrations [1] .
Vitamin C stimulated interferon production in vitro
when incubated with cultured mouse cells and in vivo
when administered to mice [42] . There is evidence that
ascorbic acid may also have antiviral activity in vivo [43,
44] . Topical application of ascorbic acid in patients with
herpes simplex virus infections decreased the duration of
the lesions and viral shedding [45] .
Zinc and the Immune System
The immune-related functions of zinc have been re-
viewed recently [46] . The innate or nonspecifi c immu-
nity as the fi rst line of defense is disturbed by altered zinc
concentrations. Lowered zinc status, such as in subclini-
cal defi ciency and zinc defi ciency impairs cellular media-
tors of innate immunity such as phagocytosis by macro-
phages and neutrophils, natural killer cell activity, gen-
eration of the oxidative burst, and complement activity
[47] . These alterations are considered to be important
contributors to increased susceptibility to infections, es-
pecially during childhood. Patients on total parenteral
nutrition without zinc supplementation showed reduced
resistance to infections that was corrected by addition of
zinc to their nourishment [48] . Zinc plays an essential role
in cell-mediated and humoral immunity, as observed in
in vitro studies and in studies in zinc-defi cient subjects
[46, 49] .
Consistent fi ndings in zinc defi ciency are a decrease in
lymphocyte numbers (lymphopenia), impaired lympho-
cyte development, reduced proliferation, increased apop-
tosis, and thymic atrophy [50] . Zinc defi ciency in experi-
mental animals is associated with low thymic weight, a
progressive loss of T lymphocytes and macrophages, de-
layed hypersensitivity and cytotoxic activity, impaired B
and T cell function, and reduced antibody recall respons-
es. Zinc is an essential cofactor for the thymic hormone
thymulin, which induces several T cell markers, and pro-
motes T cell function, including allogenic cytotoxicity,
suppressor functions, and interleukin-2 production. It
also modulates cytokine release by peripheral blood nu-
clear cells and induces the proliferation of CD8+ T cells,
which function as cytotoxic cells able to recognize and kill
pathogens [49] . In experimentally induced zinc defi cien-
cy, subjects show low serum thymulin activity, impaired
T cell and natural killer cell activities, and decreased in-
terleukin-2 and interferon production [51] .
Vitamin C and Zinc and Infectious Diseases
Vitamin C and zinc have been demonstrated to sup-
port important functions, which are essential in main-
taining health. Especially, their role in modulating host
resistance to infectious agents is considered of impor-
tance. Thus, undernutrition and defi ciency of these nu-
trients may already result in profound effects on overall
immune function with increased susceptibility to oxida-
tive stress and subsequent respiratory infections. Micro-
nutrient defi ciencies are quite common in the elderly and
even apparently healthy elderly, e.g. in European coun-
tries, were shown to have low dietary intake of at least
one nutrient [52] . Vitamin C intakes were reported in the
SENECA study to be insuffi cient in about 5–10% of the
elderly population in Europe [53] . But, also heavy chron-
ic smokers, exposed to continuous increased oxidative
stress, are known to have a reduced vitamin C status. The
NHANES III study showed signifi cantly lower leukocyte
vitamin C concentrations in smokers than in nonsmokers
[54] . This may be of importance, since the immune sys-
tem also becomes activated by environmental pollutants,
Potential of Vitamin C and Zinc in
Immune Function
Ann Nutr Metab 2006;50:85–94
89
burns, injury, exposure to radiation, and the presence of
chronic infl ammation. The proinfl ammatory cytokines
will indirectly ensure that vitamin C, and other antioxi-
dants, are released from host tissues and made available
for antioxidant defense. If not re-supplied, the host is at
risk of developing a defi ciency state.
Similarly to vitamin C, the body has no storage system
for zinc; a steady intake of zinc is thus necessary. Zinc
defi ciency in developed countries is rather seldom, but
risk groups for zinc undernutrition and zinc defi ciency
include vegetarians (decreased absorption), elderly (in-
suffi cient dietary intake), patients with intestinal diseases
(causing decreased absorption), children, pregnant and
nursing women, and patients with chronic infections or
infl ammatory diseases often seen especially in the elderly
(increased requirement) [55] . The NHANES III study in
the US reported groups at greatest risk of inadequate zinc
intake to be children aged 1–3 years, adolescent females
aged 12–19 years, and elderly people aged 1 71 years [56] .
In developing countries, infections very often coexist
with multiple nutritional defi ciencies which may be the
result of general malnutrition. Especially children, in the
case of zinc, and the elderly for both nutrients are af-
fected.
Vitamin C as well as zinc supplementation has been
shown to be of therapeutic value in specifi c clinical con-
ditions. In Chediak-Higashi syndrome, which is charac-
terized by clinical phagocytic cell dysfunction, in chronic
granulomatous disease, and in recurrent furunculosis, vi-
tamin C supplementation increases neutrophil chemo-
taxis, improves bactericidal activity and reduces the
length of clinical illness [36, 57, 58] . The rare autosomal
recessively inherited disease acrodermatitis enteropathi-
ca, caused by impaired absorption of zinc from the
gastrointestinal tract, is characterized by dermatitis, in-
termittent diarrhea, recurrent infections, growth retarda-
tion, impaired immune function and increased suscep-
tibility to infections [59] . Zinc defi ciency was shown to
result in impaired immune function and increased sus-
ceptibility to infections [60] .
Respiratory Infections and the Common Cold
Based on its immunostimulatory properties, vitamin
C has been postulated to be effective in ameliorating
symptoms of upper respiratory tract infections, especial-
ly the common cold, and a large number of placebo-con-
trolled studies in large cohorts have been carried out to
evaluate the potential role of vitamin C supplementation
in their prevention of the common cold. The most recent
overall review evaluated 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 con-
tinuous prophylaxis or as therapy after the onset of symp-
toms [61] . A meta-analysis of 29 trials involving 11,077
study participants indicated that routine prophylaxis
with high-dose vitamin C in the normal population did
not result in a reduction in the incidence of colds (RR
0.96; 95% CI 0.92–1.00), whereas a subgroup of 6 trials
involving 642 marathon runners, skiers, and soldiers on
sub-arctic exercise showed a 50% reduction in the risk of
colds (RR 0.50; 95% CI 0.38–0.66). A consistent and sta-
tistically signifi cant benefi t in reduction of cold duration
during prophylaxis with vitamin C of 8% (95% CI 3–13%)
for adults and 13.5% (95% CI 5–21%) for children was
observed in 30 comparisons involving 9,676 respiratory
episodes. The meta-analysis of severity of episodes while
on prophylaxis with vitamin C was based on 15 trial com-
parisons with 7,054 respiratory episodes. When taking
days confi ned to home and off work or school as measure
of severity (p = 0.02) or including only studies which used
symptom severity scores (p = 0.16), the pooled results re-
vealed a difference favoring vitamin C prophylaxis, which
is of great economic importance. No signifi cant differ-
ence in cold duration or cold severity was seen versus
placebo during therapy with up to 4 g of vitamin C when
started at onset of cold symptoms, but one large trial re-
ported benefi t from an 8 g therapeutic dose at onset of
cold symptoms. The authors concluded that prophylactic
vitamin C supplementation may not be justifi ed for com-
munity use, but could be of benefi t in persons exposed to
brief periods of severe physical exercise and/or cold en-
vironment. The consistent and statistically signifi cant
small benefi ts for duration and severity in those on regu-
lar vitamin C prophylaxis point to a role for vitamin C in
respiratory defense mechanisms [61] . Elderly patients
hospitalized with acute respiratory infections (pneumo-
nia; chronic bronchitis) showed a better overall status
measured as a ‘total respiratory clinical score’ when re-
ceiving 200 mg/day of vitamin C over 4 weeks [62] .
Following exercise, increased reactive oxygen species
are produced that may exceed antioxidant defense, result-
ing in oxidative damage and the stimulation of an infl am-
matory response with increased proinfl ammatory cyto-
kine production. Ultramarathon runners may therefore
benefi t from antioxidant supplementation. Subjects sup-
plemented with 600 mg vitamin C per day showed a sig-
nifi cant decrease in the incidence of postrace upper respi-
ratory infections and were able to cope better with the
oxidative stress response resulting from strenuous exer-
cise [63] . In a more recent study, it was shown that anti-
Wintergerst /Maggini /Hornig
Ann Nutr Metab 2006;50:85–94
90
oxidant supplementation of a mixture of 1 g vitamin C
and 300 mg vitamin E over 6 weeks prevented exercise-
induced oxidative stress, measured as F2-isoprostane as
marker for lipid peroxidation [64] .
Earlier in vitro studies have shown that zinc salts, at
concentrations of about 0.1 mmol/l, possess antiviral
properties and inhibit rhinovirus replication [65] . The
effects of zinc on rhinovirus replication were found to be
related to the concentration of Zn
2+
ions and were unre-
lated to total amount of zinc. The antiviral effect of Zn
2+
ions was found to be as effective as that of interferon [66] .
Alternatively, zinc salts may protect plasma membranes
against lysis by cytotoxic agents, such as microbial toxins
[67] .
On the basis of antiviral interaction, several random-
ized and placebo-controlled clinical trials were carried
out, mainly with lozenges of zinc gluconate. Several meta-
analyses were conducted, including 8 clinical trials [68] ,
and 7 clinical trials [69] . The summary odds ratio for the
presence of any cold symptoms at day 7 was 0.50 (95%
CI 0.19–1.29), and the authors concluded that convincing
evidence for the effectiveness of zinc gluconate lozenges
in reducing the common cold is lacking, but methodolog-
ical fl aws and small sample size made a defi nitive conclu-
sion diffi cult [68] . The meta-analysis by the Cochrane
Collaboration also concluded that there was no convinc-
ing evidence for zinc gluconate lozenges, since 4 trials
have shown that zinc may be effective in the treatment
of the common cold by reducing the duration and sever-
ity of symptoms, whereras 4 other trials have shown no
benefi t. But it was stated that due to diffi culties with re-
spect to blinding and bioavailability of zinc from the loz-
enges better designed studies are necessary before a fi nal
conclusion can be drawn [69] . Whereas most trials were
carried out on patients with community-acquired infec-
tions, in two studies volunteers were inoculated with rhi-
novirus, but the authors reported opposite fi ndings [70,
71] . As a treatment, zinc gluconate lozenges (containing
23 mg; 1 lozenge/2 waking hours for a total of 12 lozeng-
es/day for 4.5 days; 12 volunteers) shortened experimen-
tally induced rhinovirus-2 colds by a statistically signifi -
cant average of 4.8 days [70] . The other trial was carried
out in 55 individuals with zinc gluconate lozenges (con-
taining 23 mg of zinc gluconate and 90 mg citric acid; 1
lozenge every 2 h for a total of 8 lozenges/day for 5 days).
The treatment actually was found to prolong the cold by
1 day compared to placebo [71] .
Since the Cochrane review, three trials have been re-
ported [72–74] . Prevention and treatment of rhinovirus
infection with intranasal zinc gluconate in 91 subjects did
not show any effect [72] . The effi cacy of zinc acetate and
zinc gluconate lozenges in a study on 273 subjects chal-
lenged with rhinovirus and in 281 patients with sponta-
neous colds treated by intranasal application of zinc glu-
conate signifi cantly reduced the duration of the cold from
3.5 to 2.5 days in the rhinovirus-challenged group versus
placebo. No effects were seen in the zinc acetate group.
Likewise, no effect was observed on duration and sever-
ity with both treatments in those subjects with spontane-
ous colds [73] . In the third study, the effect of zinc acetate
in reducing the duration of symptoms of the common
cold was investigated in a randomized, double-blind, and
placebo-controlled trial in 50 volunteers. The partici-
pants were recruited within 24 h of developing symptoms
and received zinc acetate lozenges containing 12.8 mg of
zinc acetate every 2–3 h while awake as long as the symp-
toms prevailed. Measurements recorded daily for 12 days
included subjective scores for sore throat, nasal discharge,
nasal congestion, hoarseness, muscle ache, fever, and
headache. Compared with the placebo group, the zinc
acetate group showed a signifi cantly shorter overall dura-
tion of cold symptoms (4.5 vs. 8.1 days; p ! 0.005), cough
(3.1 vs. 6.3 days), nasal discharge (4.1 vs. 5.8 days) and
signifi cantly decreased total severity scores for all symp-
toms (p ! 0.002). The authors concluded that zinc acetate
may be effi cacious in reducing the duration of common
cold symptoms and should be preferred over zinc gluco-
nates [74] .
Overall, the available trials on the effect of zinc on
common colds report confl icting results. However, the
observation that prospective effi cacy of zinc lozenges
might be predicted based on the zinc ion availability from
chemically different zinc lozenge formulations, may at
least partly explain the differences in clinical outcome
[75] . Zinc ion availability identifi es the potential for ab-
sorption of Zn
2+
ions at physiological pH 7.4 into oral and
oropharyngeal mucosal membranes, which is infl uenced
by components in the lozenges (chelating substances;
food acids). The analyses of zinc lozenge formulations
used with regard to their zinc ion availability showed a
linear relationship with the reduction in the duration of
common colds in days, and suggests that the lozenges
containing zinc acetate without substances minimizing
zinc ion availability (e.g. chelators such as citric acid or
tartaric acid, EDTA, amino acids; salicylic acid) should
be investigated, since 100% of zinc acetate is released as
Zn
2+
ions at physiological pH [75] . Unfortunately, these
aspects were not considered so far by any meta-analysis
of the effect of zinc on the common cold. However, the
recent effective trial with zinc acetate lozenges to reduce
Potential of Vitamin C and Zinc in
Immune Function
Ann Nutr Metab 2006;50:85–94
91
duration and severity of symptoms actually seems to sup-
port the importance of the availability of zinc ions [74] .
Thus, further carefully conducted clinical trials are neces-
sary to prove or disprove the effi cacy of zinc acetate loz-
enges against the common cold, and such trials may be of
high economic value. Nevertheless, the mechanism un-
derlying a potential effect of zinc acetate in the treatment
of the common cold is still unclear.
The Zinc Investigators’ Collaborative Group [76] eval-
uated the effect of zinc supplementation in doses ranging
from 10 to 30 mg/day in children aged 3–36 months, on
the incidence of pneumonia in a meta-analysis including
4 randomized controlled trials and found a 41% reduc-
tion (95% CI 17–59%). This fi nding was confi rmed in
children, in whom recent trials showed a 26% reduction
in the risk of pneumonia [77] . The revised pooled analy-
sis of all 5 trials showed a 34% reduction in the incidence
of pneumonia infections (95% CI 17–47%) [76, 78] . Zinc
supplementation together with antibiotics resulted in a
30% reduction versus placebo with regard to the duration
of severe pneumonia and individual markers of disease
severity (fast breathing, hypoxia), and a mean reduction
of 25% with regard to the duration of hospital stays [79] .
A benefi t of daily zinc supplementation to Bangladeshi
children with diarrhea (20 mg for 14 days) showed a sta-
tistically nonsignifi cant downward trend in the incidence
and in hospital admission for acute lower respiratory in-
fection in the intervention group [80] . A recent study
showed that zinc treatment (10 mg zinc as acetate twice
daily for 4 days) of 153 children aged 2–24 months with
acute respiratory infection signifi cantly reduced the dura-
tion of fever (p = 0.003) and very ill status (p = 0.004) in
boys, but not in girls [81] .
Effect of Nutritional Status
Viral and bacterial infections are the most common
causes of acute diarrhea. Worldwide, acute infectious di-
arrhea has a huge impact, causing over 5 million deaths
per year. The clinical condition of diarrhea does not seem
to be related to decreased vitamin C status. Zinc defi -
ciency is highly prevalent in children in developing coun-
tries due to inadequate dietary intake, lack of intake of
animal foods, and reduced bioavailability of zinc due to
a high phytate:zinc ratio in the diet [82] . The adverse ef-
fects of zinc defi ciency on the immune response are like-
ly to increase the susceptibility of children to infectious
diarrhea, and chronic or persistent diarrhea may further
compromise the zinc status and many children become
zinc defi cient due to increased fecal losses of zinc during
diarrhea [83] .
Diarrhea is clearly established to increase the rate of
loss of endogenous zinc from the intestinal mucosa [84] .
Results are available from a large number of randomized
controlled intervention trials in developing countries as-
sessing the effect of zinc supplementation in the preven-
tion of diarrhea. The Zinc Investigators’ Collaborative
Group performed a pooled analysis of trials in children
to assess the effects of zinc supplementation in the pre-
vention of diarrhea and pneumonia and found an 18%
reduction in the incidence of diarrhea. Zinc also had a
positive therapeutic effect in the treatment of acute and
persistent diarrhea (34 and 27% reduction, respectively).
Overall, zinc was found to have signifi cant therapeutic
effects in persistent diarrhea by decreasing the duration
of episodes, lowering stool frequencies, and reducing
treatment failures or deaths by 40%. These trials were
conducted in children aged between 6 months and 3 years
and zinc treatment ranged from 10 to 30 mg/day [76, 78] .
Subsequent trials in Bangladesh [85, 86] , India [87, 88] ,
and Brazil [89] replicated these fi ndings. It is thus sug-
gested that zinc supplementation could be an important
adjuvant therapy for treating acute diarrhea in children
in developing countries [85] .
Zinc is essential for several lymphocyte functions
which have been related to resistance to malaria infec-
tions, such as production of immunoglobulin IgG, inter-
feron-
, and tumor necrosis factor-
, and just like vita-
min C, it is also most important in the microbicidal activ-
ity of macrophages [31, 49]. In children with acute
malaria infection, baseline plasma zinc concentrations
are very low ( ! 9.2
mol/l) and were found to be inverse-
ly correlated with C-reactive protein and the degree of
parasitemia [90] . Cross-sectional studies showed an as-
sociation between low zinc status and increased incidence
of malaria [91] . The Zinc Against Plasmodium Study
Group evaluated the therapeutic effect of zinc adminis-
tered as an adjuvant to standard treatment in large dou-
ble-blind controlled trials and was not able to fi nd any
effect [92] , whereas zinc supplementation in patients suf-
fering from malaria infections showed on average a 36%
decrease in the incidence of febrile illness [93] .
Conclusion
Adequate intakes of vitamin C and zinc are essential
for health. These nutrients interact with the human im-
mune system by supporting immune responses and by
providing antioxidant protection to exogenously derived
and endogenously generated reactive oxygen species pro-
Wintergerst /Maggini /Hornig
Ann Nutr Metab 2006;50:85–94
92
duced during the infl ammatory response. Vitamin C
stimulates neutrophil chemotaxis and contributes to
maintaining the redox integrity of cells thereby protecting
them against reactive oxygen species. The latter are gen-
erated during the respiratory burst to kill pathogens and
are elevated in the infl ammatory response. Likewise, zinc
undernutrition or defi ciency was shown to impair cellular
mediators of innate immunity such as phagocytosis, nat-
ural killer cell activity, and the generation of oxidative
burst.
Both vitamin C and zinc have been investigated to
determine their role in the amelioration of the common
cold. Zinc salts as lozenges have been investigated for
their potential therapeutic effect on the common cold on
the basis of their direct anti-viral activity. Available trials
on the effect of oral administration of zinc salts as loz-
enges reported confl icting results and the available evi-
dence is inconclusive. However, a recent therapeutic tri-
al with zinc acetate showed a signifi cant reduction in the
overall duration of symptoms and overall severity score.
The discrepancies in clinical outcome with zinc salts on
the common cold have recently been suggested to be due
to the different zinc ion availability from these formula-
tions to the oral and oropharyngeal mucosal membranes.
Therefore, more studies are required, especially with zinc
acetate.
The current belief is that regular prophylactic intakes
of vitamin C at doses of 200 mg or more daily have no
effect on the incidence of the common cold, but may be
benefi cial in the reduction of the severity and duration of
the symptoms, suggesting that vitamin C plays some role
in the respiratory defense mechanisms. However, the el-
derly, who have been shown to have a lowered vitamin C
status and may therefore be more prone to infections,
persons exposed to continuous oxidative stress, such as
chronic smokers, and persons exposed to heavy physical
exercise and/or cold environment may benefi t from a
moderate continuous vitamin C intake.
Other vulnerable population groups include children.
Due to the high prevalence of zinc defi ciency, especially
in children in developing countries, and to the impaired
immune status, susceptibility to infectious diarrhea, ma-
laria, and pneumonia is found to be substantially in-
creased. Large intervention trials with daily intakes of
10–30 mg of zinc have shown that zinc supplementation
could be an important adjuvant therapy for treating
these infectious diseases in children in developing coun-
tries.
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... The ability of Vitamin C and Vitamin E to enhance platelet count and morphology is supported by the results of others, who demonstrated their roles in stabilizing cell membranes and reducing oxidative injury. Levamisole's role in modulating immune and hematopoietic function likely complements the actions of antioxidants (Wintergerst et al., 2006). ...
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... Zinc is crucial for maintaining skin health, controlling the secretion and production of immune regulatory factors, influencing lymphoid organ development, and synthesizing antibodies. Additionally, zinc is involved in nucleic acid and protein metabolism, indirectly affecting immune function [152]. ...
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Aging is the result of a complex interplay of physical, environmental, and social factors, leading to an increased prevalence of chronic age-related diseases that burden health and social care systems. As the global population ages, it is crucial to understand the aged immune system, which undergoes declines in both innate and adaptive immunity. This immune decline exacerbates the aging process, creating a feedback loop that accelerates the onset of diseases, including infectious diseases, autoimmune disorders, and cancer. Intervention strategies, including dietary adjustments, pharmacological treatments, and immunomodulatory therapies, represent promising approaches to counteract immunosenescence. These interventions aim to enhance immune function by improving the activity and interactions of aging-affected immune cells, or by modulating inflammatory responses through the suppression of excessive cytokine secretion and inflammatory pathway activation. Such strategies have the potential to restore immune homeostasis and mitigate age-related inflammation, thus reducing the risk of chronic diseases linked to aging. In summary, this review provides insights into the effects and underlying mechanisms of immunosenescence, as well as its potential interventions, with particular emphasis on the relationship between aging, immunity, and nutritional factors.
... Zinc is vital for cell growth and diff erentiation of both innate and humoral immune cells, and also modulate cytokine release and trigger T cell CD8 + proliferation (Wintergerst et al., 2007). Zinc is also vital for the intracellular binding of tyrosine kinase at T cell receptors, which is required for the development and activation of T lymphocytes (Wintergerst et al., 2006). Furthermore, zinc is a cofactor for 750 transcriptional factors for protein synthesis related to the immune and a cofactor for 200 enzymes involved in the formation of antioxidants, such as superoxide dismutase (SOD) and SMAD anti-inflammatory protein, by stabilizing the tertiary structure and being an essential component on the catalytic site of enzymes (Andreini et al., 2011;Gammoh & Rink, 2017). ...
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COVID-19 has become a pandemic in the last 3 years worldwide and cases cause high mortality and morbidity. To reduce COVID-19 infection, we need to keep our immune system healthy. Several nutrients have been shown to have specific abilities to increase the power of the immune system, but their use in the treatment of COVID-19 is still being debated. This review aims to determine the role of minerals and synbiotics in increasing immunity during the COVID-19 pandemic. Specific minerals such as zinc, selenium, iron and copper have promising potential to treat COVID-19 by reducing clinical impact, markers of inflammation, and improving immunological biomarkers. In addition to increasing mineral intake, maintaining a healthy immune system can also be done by improving the health of the gut microbiota. One of the therapies that is considered to have a positive impact on handling COVID-19 is using synbiotics (a combination of prebiotics and probiotics). However, the safety and efficacy of mineral and synbiotic supplementation in COVID-19 patients as adjunctive therapy still requires further research. Minerals and synbiotics can help boost the immune system and reduce symptoms during a COVID-19 infection.
... Zinc also plays an essential role in cell-mediated and humoral immunity [89]. Moreover, it can modulate the release of cytokines and the induction of CD8 T cell proliferation which are involved in defense against pathogens [90]. Its efficacy depends on the type of zinc salt used, with zinc acetate offering greater benefits than other zinc salts [91]. ...
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It is well known that during prolonged, high-intensity physical training, athletes experience a state of immunosuppression and that balanced nutrition can help maintain immunity. This review summarizes the effects (amplified by virus infection) of high-intensity, long-term exercise on immunity, critically presenting key micronutrients and supplementation strategies that can influence athletes’ performance and their immune system. The main conclusion is that micronutrient supplementation with diet could help to protect the immune system from the stress effects induced by intense physical activities. The importance of personalized supplementation has been also recommended.
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Background: Coronavirus disease 2019 (COVID-19) can cause pulmonary and systemic inflammation in both children and adults. Investigating the potential impact of micronutrient deficiencies on COVID-19 infection is of great importance. Objectives: This case-control study was designed to compare the serum levels of vitamins D and C and zinc between healthy children and children with mild or severe COVID-19 infection, as well as to investigate the impact of micronutrient deficiencies on the clinical symptoms of patients. Methods: This case-control study was conducted at a teaching hospital in Tehran, Iran. Control subjects were recruited from healthy children, and cases were included from children with mild and severe symptoms of COVID-19. Blood samples were obtained from participants to measure the levels of micronutrients and were analyzed using statistical software. Results: A total of 85 subjects were included (33 controls, 25 cases with mild symptoms, and 27 cases with severe symptoms). We found no differences in the means of serum vitamin D and vitamin C levels between the studied groups. However, the mean serum zinc level was significantly lower in severe patients compared to the controls (P < 0.01). Moreover, no significant difference was observed in the frequency of patients with micronutrient deficiencies based on their clinical conditions. Conclusions: Our findings revealed zinc deficiency in children with severe COVID-19 infection, while no significant differences were found in the mean serum levels of vitamins D and C between healthy children and patients. More studies are necessary to provide more robust evidence.
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Kombucha, a functional beverage rich in glucuronic acid, is fermented in the presence of acetic acid bacteria and yeast as the primary microorganisms. Glucuronic acid is recognized for its various physiological benefits, such as detoxification, antioxidation, and anti-inflammation. To optimize the glucuronic acid content in kombucha, various strain combinations by selecting fermented sources were accomplished. According to the experimental results, kombucha produced through co-fermentation with Pichia anomala and Komagataeibacter hansenii, with glucose-added black tea as the carbon source, exhibited the highest glucuronic acid production. A response surface methodology found that under optimized conditions of a 12.27% (w/v) carbon source concentration, a 10.07% (w/v) substrate concentration, and a 28.4 °C temperature, the highest glucuronic acid production reached 80.16 g/L, which represented a 2.39-fold increase compared to the original kombucha. Furthermore, the total polyphenol content increased by 3.87-fold, while DPPH and ABTS free radical–scavenging capacities increased by 1.86- and 2.22-fold, respectively. To sum up, these observations reveal the potential for commercial production of glucuronic acid–enriched kombucha and contribute to the development of functional food products related to kombucha in the future.
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Ovarian cancer is the most fatal of all the reproductive cancers within the female population, mainly due to its late diagnosis that limits surgery and medical treatment. Classically, ovarian cancer therapy has included conventional chemotherapy, and other therapeutic approaches are now being used to treat these patients, but the outcomes of the disease are still poor. Therefore, new strategies are needed to improve life expectancy and life quality of ovarian cancer patients. Considering that, we investigated the effect of the nutritional supplement Ocoxin Oral Solution (OOS) in ovarian cancer models. OOS contains several nutritional supplements, some of them with demonstrated antitumoral action. In vitro studies showed that OOS inhibited the proliferation of several ovarian cancer cell lines, especially of those representative of the endometrioid subtype, in a time- and dose-dependent manner. A fast cell death induction after OOS treatment was observed, and when the molecular mechanisms leading to this effect were investigated, an activation of the DNA damage checkpoint was detected, as shown by activation (phosphorylation) of CHK1 and CHK2 kinases that was followed by the phosphorylation of the target protein histone H2AX. When tested in animal models of ovarian cancer, OOS reduced tumor growth without any observed secondary effects. Moreover, such reduction in tumor proliferation was caused by the induction of DNA damage as corroborated by the in vivo phosphorylation of CHK2 and Histone H2AX. Finally, OOS potentiated the action of carboplatin or olaparib, the standard of care treatments used in ovarian clinics, opening the possibility of including OOS in combination with those standard of care agents in patients with ovarian cancer.
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Background: Zinc supplementation in young children has been associated with reductions in the incidence and severity of diarrheal diseases, acute respiratory infections, and malaria. Objective: The objective was to evaluate the potential role of zinc as an adjunct in the treatment of acute, uncomplicated falciparum malaria; a multicenter, double-blind, randomized placebo-controlled clinical trial was undertaken. Design: Children (n = 1087) aged 6 mo to 5 y were enrolled at sites in Ecuador, Ghana, Tanzania, Uganda, and Zambia. Children with fever and greater than or equal to 2000 asexual forms of Plasmodium falciparum/muL in a thick blood smear received chloroquine and were randomly assigned to receive zinc (20 mg/d for infants, 40 mg/d for older children) or placebo for 4 d. Results: There was no effect of zinc on the median time to reduction of fever (zinc group: 24.2 h; placebo group: 24.0 h P = 0.37), a greater than or equal to 75% reduction in parasitemia from baseline in the first 72 h in 73.4% of the zinc group and in 77.6% of the placebo group (P = 0.11), and no significant change in hemoglobin concentration during the 3-d period of hospitalization and the 4 wk of follow-up. Mean plasma zinc concentrations were low in all children at baseline (zinc group: 8.54 +/- 3.93 mumol/L; placebo group: 8.34 +/- 3,25 mumol/L), but children who received zinc supplementation had higher plasma zinc concentrations at 72 h than did those who received placebo (10.95 +/- 3.63 compared with 10.16 +/- 3.25 mumol/L, P < 0.001). Conclusion: Zinc does not appear to provide a beneficial effect in the treatment of acute, uncomplicated falciparum malaria in preschool children.
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: Plasma concentrations of some micronutrients are altered in the setting of acute infectious or inflammatory stress. Previous studies have provided conflicting evidence concerning the extent and direction of changes in plasma zinc concentrations during the acute phase response. We carried out an observational cohort study in 689 children enrolled in a randomized trial of zinc supplementation during acute falciparum malaria in order to evaluate the relation between plasma zinc concentration and the acute phase response. Plasma zinc was measured by atomic absorption spectrophotometry. On admission, 70% of all subjects had low plasma zinc (<9.2 micromol/L). Multivariate analysis of predictors of admission plasma zinc showed that admission C-reactive protein (CRP), parasite density, and study site were the most important predictors. Predictors of changes in plasma zinc from admission to 72 h included baseline CRP, change in CRP, treatment group, study site, and baseline zinc concentration. In children with acute malaria infection, baseline plasma zinc concentrations were very low and were inversely correlated with CRP (r = -0.24, P < 0.0001) and the degree of parasitemia (r = -0.19, P < 0.0001). Even when CRP and time were taken into account, zinc supplementation increased plasma zinc concentration from admission to 72 h. When available, plasma zinc concentrations should be interpreted with concurrent measures of the acute phase response such as CRP. In children whose age, diet, and/or nutritional status place them at risk of zinc deficiency, those with low plasma zinc levels should be supplemented with oral zinc and followed for clinical and/or biochemical response.
Chapter
This book contains 18 chapters discussing the roles of specific nutrients in maintaining the immune response and protection against infection and non-communicable diseases, and the influence of various factors, such as exercise and aging, on the interaction between nutrition and immune function. The contents include methods for studying nutrient-immune function interactions, the impact of undernutrition on immune function and infection, the influences of fatty acids, amino acids, antioxidant vitamins, various minerals and probiotics on immunity, food allergies, immunological effects of changes throughout the life cycle, and public health policy implications.
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Background: Zinc supplementation in young children has been associated with reductions in the incidence and severity of diarrheal diseases, acute respiratory infections, and malaria. Objective: The objective was to evaluate the potential role of zinc as an adjunct in the treatment of acute, uncomplicated falciparum malaria; a multicenter, double-blind, randomized placebo-controlled clinical trial was undertaken. Design: Children (n = 1087) aged 6 mo to 5 y were enrolled at sites in Ecuador, Ghana, Tanzania, Uganda, and Zambia. Children with fever and ≥2000 asexual forms of Plasmodium falciparum/μL in a thick blood smear received chloroquine and were randomly assigned to receive zinc (20 mg/d for infants, 40 mg/d for older children) or placebo for 4 d. Results: There was no effect of zinc on the median time to reduction of fever (zinc group: 24.2 h; placebo group: 24.0 h; P = 0.37), a ≥75% reduction in parasitemia from baseline in the first 72 h in 73.4% of the zinc group and in 77.6% of the placebo group (P = 0.11), and no significant change in hemoglobin concentration during the 3-d period of hospitalization and the 4 wk of follow-up. Mean plasma zinc concentrations were low in all children at baseline (zinc group: 8.54 ± 3.93 μmol/L; placebo group: 8.34 ± 3.25 μmol/L), but children who received zinc supplementation had higher plasma zinc concentrations at 72 h than did those who received placebo (10.95 ± 3.63 compared with 10.16 ± 3.25 μmol/L, P < 0.001). Conclusion: Zinc does not appear to provide a beneficial effect in the treatment of acute, uncomplicated falciparum malaria in preschool children.
Article
OBJECTIVE: To evaluate the effect on morbidity and mortality of providing daily zinc for 14 days to children with diarrhoea. DESIGN: Cluster randomised comparison. SETTING: Matlab field site of International Center for Diarrhoeal Disease Research, Bangladesh. PARTICIPANTS: 8070 children aged 3-59 months contributed 11 881 child years of observation during a two year period. INTERVENTION: Children with diarrhoea in the intervention clusters were treated with zinc (20 mg per day for 14 days); all children with diarrhoea were treated with oral rehydration therapy. MAIN OUTCOME MEASURES: Duration of episode of diarrhoea, incidence of diarrhoea and acute lower respiratory infections, admission to hospital for diarrhoea or acute lower respiratory infections, and child mortality. RESULTS: About 40% (399/1007) of diarrhoeal episodes were treated with zinc in the first four months of the trial; the rate rose to 67% (350/526) in month 5 and to >80% (364/434) in month 7 and was sustained at that level. Children from the intervention cluster received zinc for about seven days on average during each episode of diarrhoea. They had a shorter duration (hazard ratio 0.76, 95% confidence interval 0.65 to 0.90) and lower incidence of diarrhoea (rate ratio 0.85, 0.76 to 0.96) than children in the comparison group. Incidence of acute lower respiratory infection was reduced in the intervention group but not in the comparison group. Admission to hospital of children with diarrhoea was lower in the intervention group than in the comparison group (0.76, 0.59 to 0.98). Admission for acute lower respiratory infection was lower in the intervention group, but this was not statistically significant (0.81, 0.53 to 1.23). The rate of non-injury deaths in the intervention clusters was considerably lower (0.49, 0.25 to 0.94). CONCLUSIONS: The lower rates of child morbidity and mortality with zinc treatment represent substantial benefits from a simple and inexpensive intervention that can be incorporated in existing efforts to control diarrhoeal disease.