n-3 Long-chain PUFAs reduce respiratory morbidity caused by iron supplementation in iron-deficient South African schoolchildren: a randomized, double-blind, placebo-controlled intervention

Malan, L., Baumgartner, J., Calder, P.C., Zimmermann, M.B. and Smuts, C.M. (2015) n-3 Long-chain PUFAs reduce respiratory morbidity caused by iron supplementation in iron-deficient South African schoolchildren: a randomized, double-blind, placebo-controlled intervention. American Journal of Clinical Nutrition, 101 (3), 668-679. (doi:10.3945/ajcn.113.081208). (PMID:25733652)

Abstract

BACKGROUND: Although iron supplementation in malaria-free areas mostly reduces infectious morbidity, it can sometimes increase morbidity from infections as a result of the dependence of pathogenic microorganisms on iron. Supplementation with n-3 (?-3) long-chain polyunsaturated fatty acids (LCPUFAs) improved morbidity in several human studies. However, information on the combined effect of iron and n-3 LCPUFA supplementation on infectious morbidity is limited.

OBJECTIVE: We determined whether n-3 LCPUFAs and iron supplementation, alone or in combination, affected absenteeism and illness in iron-deficient schoolchildren with low fish intake.

DESIGN: A total of 321 South African children (aged 6-11 y) with iron deficiency (ID) were randomly divided into 4 groups to receive 1) iron plus placebo, 2) a mixture of docosahexaenoic acid and eicosapentaenoic acid (DHA/EPA) plus placebo, 3) iron plus DHA/EPA, or 4) placebo plus placebo as oral supplements 4 times/wk for 8.5 mo. Morbidity was recorded, and iron-status indexes were measured. The total phospholipid fatty acid composition of peripheral blood mononuclear cell membranes was analyzed in a subsample (n = 130).

RESULTS: Iron supplementation increased the number of days with illness when all symptoms were considered (B: 0.87; 95% CI: 0.71, 1.03) as well as illness that was specifically caused by respiratory symptoms (B: 1.45; 95% CI: 1.21, 1.70), whereas DHA/EPA reduced the number of days with illness at school (B: -0.96; 95% CI: -1.33, -0.59). The increases caused by iron were reduced to the levels seen in the placebo plus placebo group when iron was provided in combination with DHA/EPA as indicated by significant iron × DHA/EPA interactions (both P < 0.001).

CONCLUSION: Iron supplementation increased morbidity (mostly respiratory) in iron-deficient South African schoolchildren with low DHA/EPA intake, but when iron was given in combination with DHA/EPA, this effect was prevented. This trial was registered at clinicaltrials.gov as NCT01092377.

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Contributors

Author: P.C. Calder

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