Iron Treatment Improves Verbal Learning and Memory of Non-Anemic but Iron- Deficient Adolescent Girls
ABSTRACT & COMMENTARY
Synopsis: Seventy-three non-anemic teenage girls with low serum ferritin levels (£ 12 mcg/dL) were randomized to receive iron supplementation or placebo for eight weeks. Increased hemoglobin levels and improvement in performance on a test for verbal learning and memory were significantly greater in girls receiving iron than in the placebo group.
Source: Bruner AB, et al. Randomized study of cognitive effects of iron supplementation in non-anemic iron deficient adolescent girls. Lancet 1996;348:992-996.
Seven-hundred sixteen girls enrolled in four Baltimore High schools were screened for non-anemic iron deficiency (normal hemoglobin; serum ferritin £ 12 mcg/dL). Seventy-three girls meeting these criteria were randomized to receive either oral ferrous sulfate or placebo for eight weeks. Girls receiving iron supplementation showed significant increases in hemoglobin and serum ferritin levels compared to a placebo group. Girls receiving iron supplementation also showed significantly improved test scores on a cognitive test assessing verbal learning and memory. Cognitive tests measuring attention were not affected by iron treatment.
COMMENT BY HOWARD A. PEARSON, MD, FAAP
The possible non-hematologic effects of iron deficiency are both controversial and provocative. Many years ago, Oski and Honig reported that iron therapy resulted in measurable improvement of behavior and developmental test scores of iron-deficient, but not necessarily anemic, infants.1
Improved iron nutrition, including use of iron-fortified infant formulas, has markedly reduced the incidence of iron-deficiency anemia on American infants. However, iron deficiency still has a significant prevalence in adolescent American girls. The Second National Health and Nutrition Examination Survey (HANES II 1976-1980) showed that 14.2% of adolescent girls were iron deficient.2
Bruner et al from Johns Hopkins studied non-anemic teenage girls from urban public high schools. Iron deficiency was defined as a serum ferritin level of 12 mcg/dL or less. Several cognitive functioning tests were administered. The girls were then randomized to receive either iron supplementation or a placebo for eight weeks.
Baseline hematology (HB, MCV, RDW) values and cognitive test scores were similar in both groups. After intervention, there was a significant increase in hemoglobin level in the iron-treated group. Test scores on the Hopkins Verbal Learning test, which assesses verbal learning and memory, were significantly improved in the iron-treated group compared to the placebo group.
I believe that this study strongly suggests that there is an effect of mild iron deficiency on cognitive function and learning in teenage girls. If one accepts the fact that iron deficiency is very prevalent in these girls, this is a pediatric and public health issue of considerable significance. It will be hard to address ways to provide dietary prophylaxis to adolescents because there is really no age-specific targeted teenage food that might be an appropriate vehicle for iron supplementation analogous to cow’s milk formulas for infants.
I don’t believe that this is necessarily a problem restricted to the inner-city locales. Some years ago, I found a 15% prevalence of iron deficiency in female students at a prestigious local private college. I am not yet ready to advise routine iron supplementation for all teenage girls, but at least we should include a careful dietary assessment when we examine adolescent girls. If the diet is marginal in iron content, it might not be a bad idea to perform a serum ferritin determination and, if this is low, consider targeted treatment. Their grades may improve!
References
1. Oski FA, Honig A. The effects of therapy on the development scores of iron-deficient infants. J Pediatr 1978; 92:21-25.
2. Expert Working Group. Summary of a report of assessment of iron status of the United States population. Am J Clin Nutr 1985;42:1318-1330.
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