Effect of preventive supplementation with zinc and other micronutrients on malaria and diarrhoeal morbidity in African children

J. Veenemans

Research output: Thesisinternal PhD, WU


Background: Zinc is important for innate and adaptive immune responses
to infection. Preventive zinc supplementation has been shown to reduce
the incidence of acute diarrhoea by 20%. Few trials have evaluated its effect
against malaria. Because trial results for both outcomes are inconsistent,
research priorities must shift from studies to measure efficacy to identifying
factors that determine the magnitude of the effect of zinc supplementation.
We hypothesized that protection by zinc supplementation depends on
concomitant supplementation with other nutrients.
Objectives: Specific objectives were: a) to assess the effect of supplementation
with zinc, alone or in combination with other nutrients, on the rates of malaria
(primary objective); b) to assess intervention effects on rates of diarrhoea and
other common diseases; c) to identify factors that determine the magnitude
of the effect of the interventions. Our studies also provided an opportunity to
assess effects of α+-thalassaemia on malaria and malaria-associated anaemia.
This haemoglobin disorder is highly prevalent in eastern Africa and that has
recently been reported to protect against severe malaria.
Methods: In a highly malaria-endemic area in rural Tanzania, we randomised
children (n=612) aged 6-60 months with height-for-age z-score ≤ –1.5 SD to
daily supplementation with: a) zinc, vitamins and other mineral elements
(‘multi-nutrients’); b) zinc; c) multi-nutrients without zinc; or d) placebo.
Those with Plasmodium infection at baseline were treated. Field staff
and participants were blinded to treatment. Sick children were detected
and evaluated in a research clinic. The primary outcome, an episode of
malaria, was pre-defined as current Plasmodium antigenaemia in children
with guardian-reported fever and any of the following: a) confirmed fever
(axillary temperature ≥ 37.5 °C), or b) unconfirmed fever with inflammation
(whole blood C-reactive protein concentrations ≥ 8 mg/L), separated by at
least 14 days from a previous malaria episode.
Results: The primary analysis included 1,572 episodes of malaria and 526
child-years of observation. The prevalence of zinc deficiency (plasma zinc
concentration < 9.9 μmol/mL) was 67% overall, and 60% in those without
inflammation (plasma C-reactive protein concentration < 8 mg/L). This
prevalence was dramatically reduced by zinc supplementation.
We found no evidence that concurrent supplementation with multi-nutrients
influenced the magnitude of the effect of zinc on rates of malaria or diarrhoea,
so that marginal effects will be presented in the remainder of this summary.
Although we found no evidence that zinc alone protected against malaria, it
reduced rates of diarrhoea by 24% (95% CI: 4%–40%) and of episodes of fever
without localising signs by 25% (4%–43%), two disorders with mutually
exclusive case definitions.
We found no effect of multi-nutrients on the overall rate of malaria episodes,
regardless the case definition used, but the effect estimate was likely
underestimated by children becoming asymptomatically infected in the
course of the intervention period. In the first 100 days of intervention, and
in the analysis of first events, supplementation with multi-nutrients, with
or without zinc, increased the hazard of malaria by one-third. In addition,
subgroup analysis indicated that this effect depended strongly on age and
iron status at baseline, with rates of episodes with parasite densities > 10,000
parasites/ μL increasing by 27 % (1%-61%) and 53% (11%–111%) in the
youngest children (6-17 months) and in children with iron deficiency, whilst
there was no evident effect in older children or those without iron deficiency
(p-values for interaction: 0.02 and 0.007).
Despite the increase in malaria rates, the children who had the lowest
haemoglobin concentrations during malaria (those aged 6-17 months)
were better able to maintain their haemoglobin concentrations when
having received multi-nutrients. Direct epidemiological evidence is
lacking, however, if and under what conditions the higher haemoglobin
concentrations during malaria (and expected reduced risk of death due to
severe malarial anemia) outweigh the possible increase in other potentially
lethal disease manifestations.
Multi-nutrient supplementation seemed to increase the rate of diarrhoea by
19% (–6% to 50%). Subgroup analysis indicated that this effect depended
on Giardia intestinalis infection at baseline (p-values for interaction: 0.03): in
those without multi-nutrients, infection was associated with a reduction in
rates of diarrhoea by 68% (34%-85%), whilst there was no evidence for such
protection in those receiving multi-nutrients. Similar effect modification was
found for fever without localizing signs.
Of 612 children in the trial, 50% had normal genotype, whilst 41% and 9%
were heterozygote and homozygous, respectively, for α+-thalassaemia. We
found no evidence of group differences in malaria rates between genotypes.
Subgroup analysis suggested, however, that the effect of α+-thalassemia
depended on age. Thus in children below 18 months, malaria rates were
increased by 30% (2%–65%) in heterozygotes, whereas they were decreased
by 20% (5%–32%) in older children (p-value for interaction: 0.001). Similar
patterns were found for homozygotes, even though estimates were less
precise due the smaller numbers of children in this age class. Based on data
from a pilot survey and a study in Kenya, we found that children with α+-
thalassaemia (particularly homozygotes) were protected against the decline in
haemoglobin concentration associated with mild to asymptomatic infections,
particularly when these infections were accompanied by inflammation.
Interpretation and conclusions for policies: We found no evidence that addition
of vitamins and other mineral elements increased the health benefits of zinc
supplements. The beneficial effects of zinc described in this thesis strengthen
the case for scaling up zinc interventions in deficient populations of African
children, without concerns that it will cause adverse effects due to malaria.
Multi-nutrient supplementation may be unsafe in malaria-endemic areas,
particularly in young children with iron deficiency. Thus the recommendation
by the World Health Organization that iron supplements should be
administered routinely to iron-deficient infants in settings with adequate
access to anti-malarial treatment is insufficiently supported by evidence and
should be reconsidered. Our results underscore that supplementation or
home fortification, even when targeting deficient subgroups in settings with
access to adequate primary care, should not be recommended in malariaendemic
areas until their safety has been demonstrated.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Wageningen University
  • Savelkoul, Huub, Promotor
  • Prentice, A.M., Promotor, External person
Award date18 Feb 2011
Print ISBNs9789085858294
Publication statusPublished - 2011


  • zinc
  • trace elements
  • food supplements
  • malaria
  • diarrhoea
  • disease prevention
  • preventive nutrition
  • children
  • tanzania
  • kenya
  • adverse effects
  • nutrient deficiencies

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