Effects of Iron Supplementation on Iron Nutrition Status and Cognitive Functions in Children

Abstract

This study examined the effect of iron supplementation on cognitive function by a double-blind intervention trial in nine-year-old mildly anaemic schoolchildren. Their nutritional status was assessed by anthropometric measurements and the following biochemical values: haemoglobin, haematocrit, red blood cell count (RBC), mean corpuscular haemoglobin (MCH), mean corpuscular volume (MCV), mean corpuscular haemoglobin concentration (MCHC), serum iron, total iron-binding capacity (TIBC), and transferrin saturation. In addition, biochemical values of vitamin A, vitamin C, thiamine, riboflavin, pyridoxine, and zinc were measured. The cognitive assessment was performed using an abbreviated Wechsler Intelligence Scale for Children-Revised (WISC-R) containing six subtests: arithmetic, similarities, digit span, picture completion, block design, and digit symbol (coding), in order to obtain information on both verbal and non-verbal aspects of intelligence. There were highly significant correlations of the WISC-R scores with initial height-for-age, haemoglobin, haematocrit, and transferrin saturation, and a correlation with MCHC. After completion of the baseline examination, one group of children was given a supplement containing 100 mg of iron for 10 weeks while the other group received a placebo. Iron supplementation had a positive effect on the biochemical measures of iron status, with haemoglobin, haematocrit, transferrin saturation, RBC, MCH, and MCHC all showing statistically significant increases ( p < .05). Iron supplementation also resulted in a statistically significant improvement in total WISC-R score ( p < .01). This effect was primarily the result of improved performance on nonverbal subtests, of which improvements in block design and coding were statistically significant ( p < .01). The small increase in the sum of scaled scores from the verbal subtest was not significant ( p > .05), but within the verbal subtest there was a significant improvement on the similarities part of the test ( p < .05). The effects of iron supplementation were more pronounced in children with initially lower haemoglobin values. It is concluded that iron supplementation in nine-year-old schoolchildren with haemoglobin levels between 110 and 119 g/L will result in an improvement of cognitive functions, even though they are not otherwise malnourished.