Micronutrient supplementation for malaria control – hype or hope?

keywords malaria control, malnutrition, micronutrient supplementation, iron, vitamin A, zinccorrespondence Olaf Mu¨ller, Department of Tropical Hygiene and Public Health,Ruprecht-Karls-University, Im Neuenheimer Feld 324, 69120 Heidelberg, Germany.E-mail: olaf.mueller@urz.uni-heidelberg.dePrevailing poverty and lack of functioning health servicesare the main reasons why malaria remains a majorcontributor to morbidity and mortality in many regions ofthe world, particularly in sub-Saharan Africa (WHO1997). Despite renewed interest in malaria control sincethe 1990s the armoury against malaria remains limited andexisting tools such as drugs and insecticides are rapidlylosing their efcacy (Marsh 1998). New tools for malariacontrol would thus be very welcome, and nutritionalinterventions have been considered to be promisingcandidates (Shankar 2000). So what is the evidence forchanges in nutritional status being effective in malariacontrol?Malnutrition is known to cause one-third to one-halfof childhood deaths and substantial proportions ofinfectious disease morbidity in developing countries(Rice et al. 2000), where young children and pregnantwomen are the groups most affected by both poornutrition and malaria. Impoverished, disease-prone envi-ronments, low levels of income and weak public healthsystems interact in a detrimental triangle. The questionof strategic health policy remains in this larger context;what role for specic interventions, and what emphasison change of the larger context of poverty and healthenvironment itself?The association between malaria and protein-energymalnutrition (PEM) has been discussed controversially fora long time. While from the 1950s until the 1980s anumber of experimental and epidemiological studiesprovided substantial evidence for PEM being associatedwith reduced malaria morbidity and mortality, this hasnot been conrmed in more recent studies (Tshikuka et al.1997; Man et al. 1998; Shankar 2000). There is also anold debate on iron and a more recent one on vitamin Aand zinc regarding their relation to malaria. In earlierstudies iron supplementation was found to be associatedwith an increased risk for malaria, a nding which couldnot be conrmed in more recent investigations (Murrayet al. 1978; Oppenheimer et al. 1986; Menendez et al.1997; Ekvall et al. 2000). In a current meta-analysiswhich included 13 trials, iron supplementation was notassociated with increased malaria infection or morbidity,but with a rise in haemoglobin levels by an average of1.2 g/dl and with a reduction in anaemia by 50%(Shankar 2000).Vitamin A and zinc deciencies are common in youngchildren in low-income countries, and both micronutrientsare considered essential for the normal functioning of theimmune system (Levin et al. 1993; Shankar & Prasad1998). Consequently vitamin A supplementation has beenshown to reduce infectious disease morbidity and all-causemortality in young children of developing countries, andthis intervention is now being widely implemented (Beatonet al. 1993; Levin et al. 1993). Zinc supplementation,given to pregnant women or young children, reducesmorbidity attributed to gastrointestinal and respiratoryinfections and has been considered likely to also reduceall-cause mortality in children of developing countries(Zinc Investigators’ Collaborative Group et al. 1999;Umeta et al. 2000; Mu¨ller et al. 2001; Osendarp et al.2001). However, results from large community-basedstudies on the effects of both vitamin A and zinc on malariaare inconclusive. While Shankar et al. (1999, 2000)reported on reduced malaria morbidity associated withboth vitamin A and zinc supplementation in pre-schoolchildren of Papua New Guinea, such effects were not