Effect of iron prophylaxis on morbidity due to infectious disease: report on clinical studies in Papua New Guinea

Comments on Background Papers Related to Iron, Folic Acid, Malaria and Other Infections

This review comments on and summarizes five expert presentations and reports made at a meeting hosted by the World Health Organization (WHO) in Lyon, France, 12–14 June 2006, related to iron and folate supplementation and their interactions with infection. The meeting was called because of the mortality implications of the Pemba iron study and the possible need to change WHO policy as soon as possible. Six tabled presentations were reviewed. A majority of these expert reviews regarded the Pemba study as indicating a specific adverse interaction between iron supplementation and malaria. A majority regarded such an effect as already reviewed, demonstrated, and predicted in existing literature published prior to the Pemba study. A majority concluded that there was a risk of malarial morbidity associated with oral iron supplementation. A majority made recommendations for change, indicating either that the 1998 WHO/UNICEF recommendation for iron supplementation in malarious areas should be suspended pending further research or that it should be stopped. A majority felt that folate supplementation was a less likely cause of the Pemba result; two mentioned the interference of oral folate with antifolate antimalarials; a majority suggested suspension of folic acid supplementation to children in malarious areas. Only one presentation argued for net population benefits of folate and none for iron.

Oral iron supplements for children in malaria-endemic areas

BACKGROUND

Iron-deficiency anaemia is common during childhood. Iron administration has been claimed to increase the risk of malaria.

OBJECTIVES

To evaluate the effects and safety of iron supplementation, with or without folic acid, in children living in areas with hyperendemic or holoendemic malaria transmission.

SEARCH METHODS

We searched the Cochrane Infectious Diseases Group Specialized Register; the Cochrane Central Register of Controlled Trials (CENTRAL), published in the Cochrane Library, MEDLINE (up to August 2015) and LILACS (up to February 2015). We also checked the metaRegister of Controlled Trials (mRCT) and World Health Organization International Clinical Trials Registry Platform (WHO ICTRP) up to February 2015. We contacted the primary investigators of all included trials, ongoing trials, and those awaiting assessment to ask for unpublished data and further trials. We scanned references of included trials, pertinent reviews, and previous meta-analyses for additional references.

SELECTION CRITERIA

We included individually randomized controlled trials (RCTs) and cluster RCTs conducted in hyperendemic and holoendemic malaria regions or that reported on any malaria-related outcomes that included children younger than 18 years of age. We included trials that compared orally administered iron, iron with folic acid, and iron with antimalarial treatment versus placebo or no treatment. We included trials of iron supplementation or fortification interventions if they provided at least 80% of the Recommended Dietary Allowance (RDA) for prevention of anaemia by age. Antihelminthics could be administered to either group, and micronutrients had to be administered equally to both groups.

DATA COLLECTION AND ANALYSIS

The primary outcomes were clinical malaria, severe malaria, and death from any cause. We assessed the risk of bias in included trials with domain-based evaluation and assessed the quality of the evidence using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. We performed a fixed-effect meta-analysis for all outcomes and random-effects meta-analysis for hematological outcomes, and adjusted analyses for cluster RCTs. We based the subgroup analyses for anaemia at baseline, age, and malaria prevention or management services on trial-level data.

MAIN RESULTS

Thirty-five trials (31,955 children) met the inclusion criteria. Overall, iron does not cause an excess of clinical malaria (risk ratio (RR) 0.93, 95% confidence intervals (CI) 0.87 to 1.00; 14 trials, 7168 children, high quality evidence). Iron probably does not cause an excess of clinical malaria in both populations where anaemia is common and those in which anaemia is uncommon. In areas where there are prevention and management services for malaria, iron (with or without folic acid) may reduce clinical malaria (RR 0.91, 95% CI 0.84 to 0.97; seven trials, 5586 participants, low quality evidence), while in areas where such services are unavailable, iron (with or without folic acid) may increase the incidence of malaria, although the lower CIs indicate no difference (RR 1.16, 95% CI 1.02 to 1.31; nine trials, 19,086 participants, low quality evidence). Iron supplementation does not cause an excess of severe malaria (RR 0.90, 95% CI 0.81 to 0.98; 6 trials, 3421 children, high quality evidence). We did not observe any differences for deaths (control event rate 1%, low quality evidence). Iron and antimalarial treatment reduced clinical malaria (RR 0.54, 95% CI 0.43 to 0.67; three trials, 728 children, high quality evidence). Overall, iron resulted in fewer anaemic children at follow up, and the end average change in haemoglobin from base line was higher with iron.

AUTHORS' CONCLUSIONS

Iron treatment does not increase the risk of clinical malaria when regular malaria prevention or management services are provided. Where resources are limited, iron can be administered without screening for anaemia or for iron deficiency, as long as malaria prevention or management services are provided efficiently.

Dietary and prophylactic iron supplements : Helpful or harmful?

Mild hypoferremia represents an aspect of the ability of the body to withhold iron from pathogenic bacteria, fungi, and protozoa, and from neoplastic cells. However, our iron-withholding defense system can be thwarted by practices that enhance iron overload such as indiscriminate iron fortification of foods, medically prescribed iron supplements, alcohol ingestion, and cigarette smoking. Elevated standards for normal levels of iron can be misleading and even dangerous for individuals faced with medical insults such as chronic infection, neoplasia, cardiomyopathy, and arthritis. We are becoming increasingly aware that the wide-spread hypoferremia in human populations is a physiological response to insult rather than a pathological cause of insult, and that attempts to correct the condition by simply raising iron levels may not only be misguided but may actually impair host defense.

Iron and infection: narrative review of a major iron supplementation study in Papua New Guinea undertaken by the Department of Tropical Paediatrics, Liverpool School of Tropical Medicine, 1979-1983, its aftermath and the continuing relevance of its results

In 1978, I returned from a 2-year government posting as provincial paediatrician to East and West Sepik provinces of Papua New Guinea (PNG), having already enrolled on the Diploma of Tropical Medicine and Hygiene (DTM&H) course at the Liverpool School of Tropical Medicine. I had been too late to enrol for the more relevant Diploma in Tropical Paediatrics course, but, whilst on the DTM&H course, made up for lost time by presenting myself to Professor Ralph Hendrickse in his office. I outlined my proposal for a double-blind, controlled, randomised trial of iron intervention with the aim of improving iron nutrition and decreasing susceptibility to and morbidity from infections in a cohort of infants in PNG. My reason for suggesting such a study was the high rate of anaemia in infants there and my perception from the literature of the time that the balance of studies favoured a beneficial effect of iron supplementation on infectious susceptibility, and that iron deficiency was associated with reversible abnormalities of immune function (although it had and has since been difficult to demonstrate the severity and relevance of these in observational in-vivo studies in humans).1,2 Ralph made an on-the-spot decision, immediately offering me the opportunity to join his department on 1 January 1979 on temporary funding while I applied for (and secured) a major grant from the Wellcome Trust for this work.

Oral iron supplements for children in malaria-endemic areas

BACKGROUND

Iron-deficiency anaemia is common during childhood. Iron supplementation has been claimed to increase the risk of malaria.

OBJECTIVES

To assess the effect of iron on malaria and deaths.

SEARCH STRATEGY

We searched The Cochrane Library, PUBMED, MEDLINE, LILACS; and trial registry databases, all up to June 2011. We scanned references of included trials.

SELECTION CRITERIA

Individually and cluster randomized controlled trials conducted in hypoendemic to holoendemic malaria regions and including children below 18 years of age. We included trials comparing orally administered iron, iron with antimalarial treatment, or iron with folic acid versus placebo or no treatment. Iron fortification was excluded. Antihelminthics could be administered to either group. Additional micronutrients had to be administered equally to both groups.

DATA COLLECTION AND ANALYSIS

The primary outcomes were clinical (symptomatic) malaria, severe malaria, and death. Two authors independently selected the studies and extracted the data. We assessed heterogeneity and conducted subgroup analyses by the presence of anaemia at baseline, age, and malaria endemicity. We assessed risk of bias using domain-based evaluation. We performed a fixed-effect meta-analysis for all outcomes and random-effects meta-analysis for hematological outcomes. We adjusted analyses for cluster randomized trials.

MAIN RESULTS

Seventy-one trials (45,353 children) were included. For clinical malaria, no significant difference between iron alone and placebo was detected, (risk ratio (RR) 0.99, 95% confidence intervals (CI) 0.90 to 1.09, 13 trials). The results were similar in the subgroups of non-anaemic children and children below 2 years of age. There was no significant difference in deaths in hyper- and holoendemic areas, risk difference +1.93 per 1000 children (95% CI -1.78 to 5.64, 13 trials, 17,898 children). Iron administered for treatment of anaemia resulted in a larger increase in haemoglobin than iron given for prevention, and the benefit was similar in hyper- or holoendemic and lower endemicity settings. Iron and folic acid supplementation resulted in mixed results for severe malaria. Overall, the risk for clinical malaria was higher with iron or with iron plus folic acid in trials where services did not provide for malaria surveillance and treatment. Iron with antimalarial treatment significantly reduced malaria. Iron supplementation during an acute attack of malaria did not increase the risk for parasitological failure, (RR 0.96, 95% CI 0.74 to 1.24, three trials) or deaths.

AUTHORS' CONCLUSIONS

Iron alone or with antimalaria treatment does not increase the risk of clinical malaria or death when regular malaria surveillance and treatment services are provided. There is no need to screen for anaemia prior to iron supplementation.

Iron deficiency: beyond anemia

Iron deficiency is the most common nutritional disorder affecting at least one third of world's population. Though anemia is common manifestation of iron deficiency, other effects of iron deficiency on various tissues, organs and systems are usually under recognized. Impaired brain development and cognitive, behavioural and psychomotor impairment are most worrisome manifestations of iron deficiency. Studies have demonstrated that some of these changes occurring during period of brain growth spurt (<2 years age) may be irreversible. Association of iron deficiency with febrile seizures, pica, breath holding spells, restless leg syndrome and thrombosis is increasingly being recognized. Impaired cell-mediated immunity and bactericidal function are generally noted in iron-deficient persons; however, the findings are inconsistent. Despite proven reversible functional immunological defects in vitro studies, a clinically important relationship between states of iron deficiency and susceptibility to infections remains controversial. Studies from malaria endemic regions have reported increased incidence of malaria in association with iron supplementation. These and some other aspects of iron deficiency are reviewed in this article.

Oral iron supplementation for preventing or treating anaemia among children in malaria-endemic areas

BACKGROUND

Iron-deficiency anaemia is common during childhood. Iron supplementation has been claimed to increase the risk of malaria.

OBJECTIVES

To assess the effect of iron on malaria and deaths.

SEARCH STRATEGY

We searched The Cochrane Library (2009, issue 1); MEDLINE; EMBASE; LILACS and metaRegister of Controlled Trials, all up to March 2009. We scanned references of included trials.

SELECTION CRITERIA

Individually and cluster-randomized controlled trials conducted in hypoendemic to holoendemic malaria regions and including children < 18 years. We included trials comparing orally administered iron with or without folic acid vs. placebo or no treatment. Iron fortification was excluded. Antimalarials and/or antiparasitics could be administered to either group. Additional micronutrients could only be administered equally to both groups.

DATA COLLECTION AND ANALYSIS

The primary outcomes were malaria-related events and deaths. Secondary outcomes included haemoglobin, anaemia, other infections, growth, hospitalizations, and clinic visits. We assessed risk of bias using domain-based evaluation. Two authors independently selected studies and extracted data. We contacted authors for missing data. We assessed heterogeneity. We performed fixed-effect meta-analysis and presented random-effects results when heterogeneity was present. We present pooled risk ratios (RR) with 95% confidence intervals (CIs). We used adjusted analyses for cluster-randomized trials.

MAIN RESULTS

Sixty-eight trials (42,981 children) fulfilled the inclusion criteria. Iron supplementation did not increase the risk of clinical malaria (RR 1.00, 95% CI 0.88 to 1.13; 22,724 children, 14 trials, random-effects model). The risk was similar among children who were non-anaemic at baseline (RR 0.96, 95% CI 0.85 to 1.09). An increased risk of malaria with iron was observed in trials that did not provide malaria surveillance and treatment. The risk of malaria parasitaemia was higher with iron (RR 1.13, 95% CI 1.01 to 1.26), but there was no difference in adequately concealed trials. Iron + antimalarial was protective for malaria (four trials). Iron did not increase the risk of parasitological failure when given during malaria (three trials). There was no increased risk of death across all trials comparing iron versus placebo (RR 1.11, 95% CI 0.91 to 1.36; 21,272 children, 12 trials). Iron supplementation increased haemoglobin, with significant heterogeneity, and malaria endemicity did not affect this effect. Growth and other infections were mostly not affected by iron supplementation.

AUTHORS' CONCLUSIONS

Iron does not increase the risk of clinical malaria or death, when regular malaria surveillance and treatment services are provided. There is no need to screen for anaemia prior to iron supplementation.

Micronutrient supplementation affects maternal-infant feeding interactions and maternal distress in Bangladesh

BACKGROUND

Good maternal-infant interaction is essential for optimal infant growth, health, and development. Although micronutrient malnutrition has been associated with poorer interaction, the effects of maternal micronutrient supplementation on interaction are unknown.

OBJECTIVES

We examined differences in maternal-infant feeding interaction between 3 maternal pre- and postpartum micronutrient supplementation groups that differed in iron dose and inclusion of multiple micronutrients and determined whether any differences observed were mediated by maternal distress.

DESIGN

A cohort of 180 pregnant women was selected from 3300 women in the randomized controlled trial Maternal Infant Nutritional Interventions Matlab, which was conducted in Matlab, Bangladesh. At 8 wk of gestation, women were randomly assigned to 1 of 3 groups to receive a daily supplement of micronutrients (14 wk gestation to 12 wk postpartum): 60 or 30 mg Fe each with 400 microg folic acid or multiple micronutrients (MuMS; 30 mg Fe, 400 microg folic acid, and other micronutrients). A maternal-infant feeding interaction was observed in the home when infants were 3.4-4.0 mo of age, and maternal distress was assessed.

RESULTS

Compared with 30 mg Fe, 60 mg Fe decreased the quality of maternal-infant feeding interaction by approximately 10%. Compared with 30 mg Fe, MuMS did not improve interaction but reduced maternal early postpartum distress. Distress did not mediate the effects of micronutrient supplementation on interaction.

CONCLUSION

For pregnant and postpartum women, micronutrient supplementation should be based on both nutritional variables (eg, iron status) and functional outcomes (eg, maternal-infant interaction and maternal distress).

The Comparative Impact of Iron, the B-Complex Vitamins, Vitamins C and E, and Selenium on Diarrheal Pathogen Outcomes Relative to the Impact Produced by Vitamin A and Zinc

Micronutrient supplementation offers one of the most cost-effective means of improving the health and survival of children in developing countries. However, the effects of supplementation with single micronutrients on diarrhea are not always consistent, and supplementation with multi-micronutrient supplements can have negative effects. These inconsistencies may result from the failure to consider the diverse etiological agents that cause diarrhea and the unique effects each micronutrient has on the immune response to each of these agents. This review examines the separate effects that supplementation with the B-complex vitamins, vitamin C, vitamin E, selenium, and iron have on diarrheal disease-related outcomes. Supplementation with iron may increase the risk of infection by invasive diarrheal pathogens, while supplementation with the remaining micronutrients may reduce this risk. These differences may be due to distinct regulatory effects each micronutrient has on the pathogen-specific immune response, as well as on the virulence of specific pathogens. The findings of these studies suggest that micronutrient supplementation of children must take into account the pathogens prevalent within communities as reflected by their diarrheal disease burdens. The effectiveness of combining multiple micronutrients into one supplement must also be reconsidered.

Iron metabolism and malaria

Recent evidence from a large, randomized, controlled trial has suggested that the universal administration of iron to children in malaria-endemic areas is associated with an increase in adverse health outcomes. The purpose of this paper is to summarize the available ecologic and intervention trials related to iron and malaria in children, and to set these against current knowledge of the biology of host-pathogen interactions involving iron metabolism. We conclude that, although not fully consistent, the balance of evidence confirms that administration of iron (usually in combination with folic acid) increases the incidence of malaria when given without prophylaxis and in the absence of universal access to treatment. The mechanisms by which additional iron can benefit the parasite are far from clear. There is evidence to suggest that the apparent detrimental effect of iron supplementation may vary according to levels of antecedent iron status, the presence of hemoglobinopathies and glucose-6-phosphate dehydrogenase (G6PD) deficiency, and other host genetic variants, such as variants in haptoglobin. The effects of malaria on host iron metabolism are also reviewed and reveal that the key cause of malaria-induced anemia is a maldistribution of iron and suppression of erythropoiesis rather than an exacerbation of gross iron deficiency. We tentatively conclude that, if it is to be recommended, universal iron supplementation in malarious areas should only be considered in conjunction with some form of prophylaxis (e.g., intermittent preventive therapy [IPT]) or in the context of good health services with ready access to facilities for malaria diagnosis and treatment. An alternative approach would be to screen for anemia and target supplementation only to anemic children. With regard to treatment, there is good evidence that iron supplementation should be withheld until the treatment schedule is complete, both because iron may inhibit treatment and because the absorption of oral iron is blocked by the inflammatory response.

Randomized controlled trial of the effect of daily supplementation with zinc or multiple micronutrients on the morbidity, growth, and micronutrient status of young Peruvian children

BACKGROUND

Zinc supplements reduce childhood morbidity in populations in whom zinc deficiency is common. In such populations, deficiencies in other micronutrients may also occur.

OBJECTIVE

The objective was to determine whether the administration of other micronutrients with zinc modifies the effect of zinc supplementation on children's morbidity and physical growth.

DESIGN

Two hundred forty-six children aged 6-35 mo with persistent diarrhea were randomly assigned to 1 of 3 groups to receive a daily supplement of 10 mg Zn alone (Zn; n = 81), zinc plus vitamins and other minerals at 1-2 times recommended daily intakes (Zn+VM; n = 82), or placebo (n = 83) for approximately 6 mo after the diarrhea episode ended. Morbidity information was collected on weekdays. Weight, length, and other anthropometric indicators were measured monthly, and plasma zinc and other indicators of micronutrient status were measured at baseline and 6 mo.

RESULTS

Supplement consumption was high ( approximately 90%) in all groups, although slightly more vomiting was reported in the Zn+VM group (P < 0.0001, analysis of variance). The change in plasma zinc from baseline to 6 mo was greater in the 2 zinc groups (6.1, 27.3, and 16.2 micro g/dL in the placebo, Zn, and Zn+VM groups, respectively; P < 0.0001, analysis of variance). The Zn group had fewer episodes of diarrhea, dysentery, and respiratory illness and a lower prevalence of fever and cough than did the Zn+VM group and a lower prevalence of cough than did the placebo group (P = 0.05). No significant effects of supplementation on growth were observed.

CONCLUSION

Morbidity was greater after supplementation with zinc plus multivitamins and minerals than it was after supplementation with zinc alone.

Effect of iron supplementation on incidence of infectious illness in children: systematic review

OBJECTIVE

To evaluate the effect of iron supplementation on the incidence of infections in children.

DESIGN

Systematic review of randomised controlled trials.

DATA SOURCES

28 randomised controlled trials (six unpublished and 22 published) on 7892 children.

INTERVENTIONS

Oral or parenteral iron supplementation or fortified formula milk or cereals.

OUTCOMES

Incidence of all recorded infectious illnesses, and individual illnesses, including respiratory tract infection, diarrhoea, malaria, other infections, and prevalence of positive smear results for malaria.

RESULTS

The pooled estimate (random effects model) of the incidence rate ratio (iron v placebo) was 1.02 (95% confidence interval 0.96 to 1.08, P=0.54; P<0.0001 for heterogeneity). The incidence rate difference (iron minus placebo) for all recorded illnesses was 0.06 episodes/child year (-0.06 to 0.18, P=0.34; P<0.0001 for heterogeneity). However, there was an increase in the risk of developing diarrhoea (incidence rate ratio 1.11, 1.01 to 1.23, P=0.04), but this would not have an overall important on public health (incidence rate difference 0.05 episodes/child year, -0.03 to 0.13; P=0.21). The occurrence of other illnesses and positive results on malaria smears (adjusted for positive smears at baseline) were not significantly affected by iron administration. On meta-regression, the statistical heterogeneity could not be explained by the variables studied.

CONCLUSION

Iron supplementation has no apparent harmful effect on the overall incidence of infectious illnesses in children, though it slightly increases the risk of developing diarrhoea.

Developmental trajectories of poorly nourished toddlers that received a micronutrient supplement with and without energy

Experimental and quasi-experimental studies on the effects of nutritional supplements on development in young children generally include snapshots of development. Developmental outcomes are better revealed when multiple assessments are made over time. We compared the effects of a micronutrient intervention with and without supplementary energy on the mental and motor growth curves of poorly nourished toddlers in West Java. Subjects (12-mo-old cohort, n = 33; 18-mo-old cohort, n = 42) were randomly assigned to receive energy + micronutrients (E + M) or micronutrients (M) daily for 12 mo. The cohort/treatment groups were then classified as either relatively short or tall. Within the 12-mo cohort, the baseline mean length Z-scores ranged from -2.53 to -1.29 and the baseline mean weight Z-scores ranged from -3.05 to -2.18. The same pretreatment anthropometrics for the older cohort ranged from -3.22 to -1.59 and from -3.42 to -2.26. Mental and motor development scores (Bayley) were obtained at baseline and every 2 mo for 12 mo. There was a Cohort x Length Category x Supplement interaction for mental slopes (P < 0.01). Slopes for tall-E + M (b = 5.35) and tall-M children (b = 5.39) in the 18-mo cohort were equivalent, but slopes for short-E + M (b = 6.13) and short-M (b = 4.67) children differed greatly (P = 0.03). On the basis of this finding and findings previously reported from this study, we concluded that the unfavorable developmental response to the M supplement that was restricted to the shortest children within an already disadvantaged group.

Micronutrient deficiency in children

Malnutrition increases morbidity and mortality and affects physical growth and development, some of these effects resulting from specific micronutrient deficiencies. While public health efforts must be targeted to improve dietary intakes in children through breast feeding and appropriate complementary feeding, there is a need for additional measures to increase the intake of certain micronutrients. Food-based approaches are regarded as the long-term strategy for improving nutrition, but for certain micronutrients, supplementation, be it to the general population or to high risk groups or as an adjunct to treatment must also be considered. Our understanding of the prevalence and consequences of iron, vitamin A and iodine deficiency in children and pregnant women has advanced considerably while there is still a need to generate more knowledge pertaining to many other micronutrients, including zinc, selenium and many of the B-vitamins. For iron and vitamin A, the challenge is to improve the delivery to target populations. For disease prevention and growth promotion, the need to deliver safe but effective amounts of micronutrients such as zinc to children and women of fertile age can be determined only after data on deficiency prevalence becomes available and the studies on mortality reduction following supplementation are completed. Individual or multiple micronutrients must be used as an adjunct to treatment of common infectious diseases and malnutrition only if the gains are substantial and the safety window sufficiently wide. The available data for zinc are promising with regard to the prevention of diarrhea and pneumonia. It should be emphasized that there must be no displacement of important treatment such as ORS in acute diarrhea by adjunct therapy such as zinc. Credible policy making requires description of not only the clinical effects but also the underlying biological mechanisms. As findings of experimental studies are not always feasible to extrapolate to humans, the biology of deficiency as well as excess of micronutrients in humans must continue to be investigated with vigour.

Iron and inflammatory bowel disease

Both anaemia of iron deficiency and anaemia of chronic disease are frequently encountered in inflammatory bowel disease. Anaemia of iron deficiency is mostly due to inadequate intake or loss of iron. Anaemia of chronic disease probably results from decreased erythropoiesis, secondary to increased levels of proinflammatory cytokines, reactive oxygen metabolites and nitric oxide. Assessment of the iron status in a condition associated with inflammation, such as inflammatory bowel disease, is difficult. The combination of serum transferrin receptor with ferritin concentrations, however, allows a reliable assessment of the iron deficit. The best treatment for anaemia of chronic disease is the cure of the underlying disease. Erythropoietin reportedly may increase haemoglobin levels in some of these patients. The anaemia of iron deficiency is usually treated with oral iron supplements. Iron supplementation may lead to an increased inflammatory activity through the generation of reactive oxygen species. To date, data from studies in animal models of inflammatory bowel disease support the theoretical disadvantage of iron supplementation in this respect. The results, however, cannot easily be extrapolated to the human situation, because the amount of supplemented iron in these experiments was much higher than the dose used in patients with iron deficiency.

An analysis of anemia and child mortality

The relationship of anemia as a risk factor for child mortality was analyzed by using cross-sectional, longitudinal and case-control studies, and randomized trials. Five methods of estimation were adopted: 1) the proportion of child deaths attributable to anemia; 2) the proportion of anemic children who die in hospital studies; 3) the population-attributable risk of child mortality due to anemia; 4) survival analyses of mortality in anemic children; and 5) cause-specific anemia-related child mortality. Most of the data available were hospital based. For children aged 0-5 y the percentage of deaths due to anemia was comparable for reports from highly malarious areas in Africa (Sierra Leone 11.2%, Zaire 12.2%, Kenya 14.3%). Ten values available for hemoglobin values <50 g/L showed a variation in case fatality from 2 to 29.3%. The data suggested little if any dose-response relating increasing hemoglobin level (whether by mean value or selected cut-off values) with decreasing mortality. Although mortality was increased in anemic children with hemoglobin <50 g/L, the evidence for increased risk with less severe anemia was inconclusive. The wide variation for mortality with hemoglobin <50 g/L is related to methodological variation and places severe limits on causal inference; in view of this, it is premature to generate projections on population-attributable risk. A preliminary survival analysis of an infant cohort from Malawi indicated that if the hemoglobin decreases by 10 g/L at age 6 mo, the risk of dying becomes 1.72 times higher. Evidence from a number of studies suggests that mortality due to malarial severe anemia is greater than that due to iron-deficiency anemia. Data are scarce on anemia and child mortality from non-malarious regions. Primary prevention of iron-deficiency anemia and malaria in young children could have substantive effects on reducing child mortality from severe anemia in children living in malarious areas.

Iron and its relation to immunity and infectious disease

The continuing unresolved debate over the interaction of iron and infection indicates a need for quantitative review of clinical morbidity outcomes. Iron deficiency is associated with reversible abnormalities of immune function, but it is difficult to demonstrate the severity and relevance of these in observational studies. Iron treatment has been associated with acute exacerbations of infection, in particular, malaria. Oral iron has been associated with increased rates of clinical malaria (5 of 9 studies) and increased morbidity from other infectious disease (4 of 8 studies). In most instances, therapeutic doses of oral iron were used. No studies in malarial regions showed benefits. Knowledge of local prevalence of causes of anemia including iron deficiency, seasonal malarial endemicity, protective hemoglobinopathies and age-specific immunity is essential in planning interventions. A balance must be struck in dose of oral iron and the timing of intervention with respect to age and malaria transmission. Antimalarial intervention is important. No studies of oral iron supplementation clearly show deleterious effects in nonmalarious areas. Milk fortification reduced morbidity due to respiratory disease in two very early studies in nonmalarious regions, but this was not confirmed in three later fortification studies, and better morbidity rates could be achieved by breast-feeding alone. One study in a nonmalarious area of Indonesia showed reduced infectious outcome after oral iron supplementation of anemic schoolchildren. No systematic studies report oral iron supplementation and infectious morbidity in breast-fed infants in nonmalarious regions.

Nutrition and maternal mortality in the developing world

This review relates nutritional status to pregnancy-related death in the developing world, where maternal mortality rates are typically >/=100-fold higher than rates in the industrialized countries. For 3 of the central causes of maternal mortality (ie, induced abortion, puerperal infection, and pregnancy-induced hypertension), knowledge of the contribution of nutrition is too scanty for programmatic application. Hemorrhage (including, for this discussion, anemia) and obstructed labor are different. The risk of death is greatly increased with severe anemia (Hb <70 or 80 g/L); there is little evidence of increased risk associated with mild or moderate anemia. Current programs of universal iron supplementation are unlikely to have much effect on severe anemia. There is an urgent need to reassess how to approach anemia control in pregnant women. Obstructed labor is far more common in short women. Unfortunately, nutritional strategies for increasing adult stature are nearly nonexistent: supplemental feeding appears to have little benefit after 3 y of age and could possibly be harmful at later ages, inducing accelerated growth before puberty, earlier menarche (and possible earlier marriage), and unchanged adult stature. Deprived girls without intervention typically have late menarche, extended periods of growth, and can achieve nearly complete catch-up growth. The need for operative delivery also increases with increased fetal size. Supplementary feeding could therefore increase the risk of obstructed labor. In the absence of accessible obstetric services, primiparous women <1.5 m in height should be excluded from supplementary feeding programs aimed at accelerating fetal growth. The knowledge base to model the risks and benefits of increased fetal size does not exist.

Clinical safety of iron-fortified formulas

BACKGROUND

Iron-fortified formulas are recommended throughout infancy and are frequently used beyond, yet safety aspects have been inadequately studied. Iron could theoretically increase pro-oxidant stress, with potential adverse effects, including infection risk, and some clinicians suspect that iron-fortified formulas induce gastrointestinal disturbance.

OBJECTIVE

A planned component of a large intervention trial has been to test the hypothesis that infants receiving iron-fortified formula do not have a higher incidence of infections (primary outcome) or gastrointestinal problems (secondary outcome) than infants on low iron-formulas or cow's milk. Methods. Children (n = 493) 9 months old receiving cow's milk were recruited in 3 UK centers and randomized to: 1) cow's milk as before, 2) formula containing.9 mg/L of iron, or 3) an otherwise identical formula but containing 12 mg/L of iron. Children were followed at 3 monthly intervals and the episodes of infections, diarrhea and constipation, and general morbidity to 18 months old were recorded. Hematologic indices of iron status were determined at 18 months old.

RESULTS

Serum ferritin concentrations were increased in infants receiving iron-fortified formula but there were no intergroup differences in incidence of infection, gastrointestinal problems, or in general morbidity or weight gain.

CONCLUSIONS

We were unable to identify adverse health effects in older infants and toddlers consuming a high iron-containing formula (12 mg/L) even when used in populations with a low incidence of iron deficiency.

Iron and infection in the tropics: paediatric clinical correlates

Iron deficiency is prevalent in children worldwide. Programmes of presumptive therapy, mass supplementation and food fortification have been introduced in many countries. The continuing unresolved debate over the interaction of iron and infection in the clinical setting indicates the need for firm guidelines for these practices. Iron overload is associated with increased susceptibility to certain infections, although the exact mechanisms may vary with the main pathology. Iron treatment has been associated with acute exacerbations of infection, in particular malaria. In Papua New Guinea parenteral iron was associated with increased rates of malaria and increased morbidity due to respiratory disease in infants but not in school children. Several subsequent studies in Africa using oral iron showed deleterious effects. In most instances cited, immunity was compromised, and therapeutic doses of oral iron were used. Knowledge of malarial endemicity, immunity with respect to age and the prevalence of haemoglobinopathies is important in planning interventions. A fine balance needs to be struck in the timing and dose of oral iron if informed recommendations are to be made. In parallel with supplementation studies, the effects of iron chelation on infection are being reported increasingly. Such therapy is clearly protective against malaria and some other infections but may predispose to fungal and Yersinia infections.

Bound iron admixture prevents the spontaneous generation of peroxides in total parenteral nutrition solutions

BACKGROUND

Parenteral administration of iron is a matter of controversy because it is feared that it could contribute to oxidative reactions. The aim of this study was to verify if irondextran participates in the redox reactions occurring in total parenteral nutrition (TPN) solutions.

METHODS

Irondextran was compared with different forms of iron in the interaction with peroxides. Hydroperoxide levels were measured by a colorimetric technique in TPN solutions, in presence of varying sources (FeCl2, FeSO4, irondextran, iron sorbitol) and concentrations (0-0.8 mM) of iron. The consumption and inhibition of peroxide generation were tested by analyzing the effect of iron on different sources of peroxides (H2O2, tert-butyl and cumen hydroperoxide). The free radicals produced under conditions of a Fenton-like reaction were measured by the oxidation of scopoletin. And the proportion of Fe3+ freed by both bound-iron sources was counted by measuring the masking effect on the thiol function of cysteine.

RESULTS

Free-iron admixture to parenteral nutrition induces the formation of free radicals, whereas sources of bound-iron inhibit the generation of peroxides in parenteral nutrition without implying a Fenton-like reaction.

CONCLUSION

For patients requiring iron supplementation, bound-iron should be added during the preparation of TPN solutions, because it protects against the spontaneous generation of peroxides.

Iron, anemia, and infection

The data on the relationship between iron deficiency and infection are conflicting. Some researchers conclude that mild iron deficiency is beneficial for immunity, whereas others contend that any deficit is not good for immunity. Additionally, infection or inflammation generate anemia and profound changes in iron metabolism mediated by cytokines. These changes are important confounders to consider in assessments of iron status.

In vitro activities of novel catecholate siderophores against Plasmodium falciparum

The activities of novel iron chelators, alone and in combination with chloroquine, quinine, or artemether, were evaluated in vitro against susceptible and resistant clones of Plasmodium falciparum with a semimicroassay system. N4-nonyl,N1,N8-bis(2,3-dihydroxybenzoyl) spermidine hydrobromide (compound 7) demonstrated the highest level of activity: 170 nM against a chloroquine-susceptible clone and 1 microM against a chloroquine-resistant clone (50% inhibitory concentrations). Compounds 6, 8, and 10 showed antimalarial activity with 50% inhibitory concentrations of about 1 microM. Compound 7 had no effect on the activities of chloroquine, quinine, and artemether against either clone, and compound 8 did not enhance the schizontocidal action of either chloroquine or quinine against the chloroquine-resistant clone. The incubation of compound 7 with FeCI3 suppressed or decreased the in vitro antimalarial activity of compound 7, while no effect was observed with incubation of compound 7 with CuSO4 and ZnSO4. These results suggest that iron deprivation may be the main mechanism of action of compound 7 against the malarial parasites. Chelator compounds 7 and 8 primarily affected trophozoite stages, probably by influencing the activity of ribonucleotide reductase, and thus inhibiting DNA synthesis.

Lack of association between levels of transplacentally acquired Plasmodium falciparum-specific antibodies and age of onset of clinical malaria in infants in a malaria endemic area of Nigeria

A cohort of 117 newborns was followed longitudinally for 12 months to determine the age of onset of clinical malaria and the subsequent episodes of malaria, and to investigate the possible existence of a correlation between level of transplacentally acquired Plasmodium falciparum-specific antibodies and age of onset of malaria in the infant. The mean age of onset of malaria in 49 infants was 4.48 +/- 1.54 months. Mean (+/- S.D.) age of onset of clinical malaria in haemoglobin AA infants (4.38 +/- 1.14) was significantly (P < 0.05) lower compared with haemoglobin AS (5.58 +/- 2.43) infants. No correlation was obtained between the age of onset of malaria and the level of cord serum total IgG, IgM and antibodies to P. falciparum antigens. Cord blood seropositivity for antibodies to the blood stage antigen Pf155/RESA and its C-terminal repeat sequence (EENV)6 or to the (NANP)6 peptide representing repeats of the circumsporozoite protein (CSP) did not influence the age of onset of clinical malaria. However, infants with haemoglobin AS whose cord blood was seropositive for antibodies to the (EENV)6 or (NANP)6 peptide showed delayed onset (P < 0.001) of malaria compared with AA seropositive infants. Although our results indicate that transplacentally acquired antibodies to the studied antigens alone offer no significant protection against malaria during the first few months of life, antibodies in concert with other factors such as haemoglobin genotype may contribute to the protection of the newborn.

Thalassaemia in Vanuatu, south-west Pacific: frequency and haematological phenotypes of young children

The archipelago of Vanuatu situated in the South-West Pacific has a high frequency of alpha + thalassaemia and additionally on some of the islands there is a high frequency of beta thalassaemia. As part of a large cohort study to investigate the clinical effect of thalassaemia on malaria on the islands of Espiritu Santo and Maewo in Vanuatu, the gene frequencies of the thalassaemias were determined and blood counts were performed on a cohort of infants from birth to 3 years. The haematological phenotypes of the different thalassaemic genotypes are compared, providing a detailed description of the clinical manifestations of alpha + thalassaemia during early development. In addition, cross-sectional surveys of the population of the two islands were performed to establish the frequency of thalassaemia and other red cell polymorphisms and their geographical distribution.

Adverse effect of iron supplementation on weight gain of iron-replete young children

The efficacy of iron supplementation for iron-deficient subjects is in no doubt. However, the assumption that iron supplementation of iron-replete subjects is harmless may not be valid. We have studied the effect of iron supplementation on growth rate in 47 iron-sufficient young children (12-18 months) in Indonesia. The children were randomly assigned either ferrous sulphate (3 mg/kg daily) or placebo every day for 4 months. Before treatment the length, weight, and arm circumference of the two groups were similar. During the 4 months of supplementation the rate of weight gain was significantly greater in the placebo group than in the iron-supplemented group (0.106 [SE 0.010] vs 0.070 [0.011] kg every 2 weeks, p = 0.02). The rates of gain in length and arm circumference did not differ significantly by treatment. There were no differences between the groups in rates of respiratory and gastrointestinal infections. These results suggest that iron supplementation of iron-replete children may retard their growth.

Azidothymidine (AZT)-induced siderosis

Azidothymidine (AZT) interferes with heme synthesis. This should upregulate the synthesis of transferrin receptors and increase the amount of iron taken up by the cell. We found a 50% increase in the iron content of liver and a 20% increase in the iron content of macrophages in AZT-treated mice.

The immune response in iron-deficient young children: effect of iron supplementation on cell-mediated immunity

The effects of iron deficiency on immunity remain controversial. This study was designed to assess the impact of iron supplementation on the immune status, in 81 children aged 6 months-3 years, at high risk for iron deficiency, using a longitudinal double blind randomised and placebo-controlled study. Lymphocytes of iron-deficient children produced less interleukin-2 in vitro. Iron supplementation for 2 months increased mean corpuscular volume, serum ferritin and serum transferrin, but had no effect on the parameters of T-cell mediated immunity. The lower interleukin-2 levels in iron-deficient suggest that cell-mediated immunity may be impaired in iron deficiency.

A randomized comparison of routine versus selective iron supplementation during pregnancy

This trial compares routine and selective iron supplementation during pregnancy to determine whether routine supplementation adversely affects fetal growth, increases infections and subjective adverse effects, and/or delays birth. At their first prenatal visit, 2912 pregnant women were randomized into two groups (2694 gave birth). Compliance was satisfactory as measured by self-reports by mothers and hematocrit values in the third trimester. More women in the routinely supplemented group had subjected adverse effects. The groups were similar in regard to most of the other outcomes. In the selectively supplemented group, there was weak evidence for increase in sick-days, referrals to hospital outpatient clinic, cesarean section, blood transfusions, and infants who were diagnosed as having hyperviscosity. In the routine group, there were somewhat more women with gestations greater than or equal to 41 weeks and more dead infants. The subgroup analyses suggest that some of the apparently worse outcomes in the selective group were due to reactions of midwives and physicians to low hematocrit values.

Iron and infection: the clinical evidence

Iron deficiency is prevalent in childhood in the developed and developing countries. Programs of presumptive therapy, mass supplementation and food fortification have been introduced in many countries. The unresolved debate over the interaction of iron and infection in the clinical setting prompts re-evaluation of these practices. Situations of iron overload are associated with increased susceptibility to certain infections, although the exact mechanisms may vary with the main pathology. Iron treatment has been associated with acute exacerbations of infection, in particular malaria. In most instances parenteral iron was used. In the neonate parenteral iron is associated with serious E. coli sepsis. In one country, with endemic malaria, parenteral iron was associated with increased rates of malaria and increased morbidity due to respiratory disease in infants. In contrast in non-malarious countries studies of oral iron supplementation have if anything shown a reduction in infectious morbidity. Methodological problems in the latter reports indicate the need for further controlled prospective studies with accurate morbidity recording if informed recommendations are to be made.

Iron and malaria

Iron deficiency is common in the developing world; consequently, programmes of presumptive therapy and mass supplementation have been introduced in several countries. In this article Stephen Oppenheimer suggests caution, as recent evidence suggests that these practices may actually increase the likelihood of the subject developing patent malaria in endemic areas. This may be especially significant in infants, who are less likely to be immune to malaria, and in pregnant women, who are often routinely given iron supplements and in whom malaria may damage the foetus.

Iron status, immune capacity and resistance to infections

1. The importance of iron on immune functions is reviewed. 2. The consequences of iron deficiency upon resistance to infection in men (adults and children) and animals are controversial. 3. Cellular immunity is often altered in iron-deficient humans and in murine species. 4. Humoral immune responses seem far less affected in iron-deficient humans than is cellular immunity, but is impaired in iron-deficient animals. Results on complement are scarce and controversial. 5. There is almost no perturbation of phagocytosis but bactericidal activity is decreased in most studies on iron-deficient subjects. 6. Natural Killer activity is decreased in iron-deficient mice. Iron deficiency also affects lymphokine production in mice and rats.