Search for nutritional confounding factors in the relationship between iron deficiency and brain function

Article Abstract:

Much evidence has been gathered that suggests iron deficiency (ID) has an adverse effect on brain function. While the mechanism is not understood, one possible explanation is that ID reduces the amounts certain substances essential for brain functioning. The practical significance of such adverse effects is that behavior and intellectual performance may be altered, particularly in children. More research is needed to firmly link ID to brain functioning, but researchers are troubled by factors that affect both ID and brain function; these confounding factors influence either ID or brain activity and their effects may mislead scientists into drawing invalid conclusions. The author reviews a certain group of confounding factors, namely nutritional factors. The three dietary factors discussed are vitamin C, phytates and lead. All three may confound or confuse interpretation of the relationship between ID and brain function. First, ascorbic acid, vitamin C, dramatically promotes absorption of iron when foods containing both nutrients are consumed at the same meal. Ascorbic acid also influences certain aspects of brain metabolism. The second dietary factor discussed is phytates, which are found in grains. Phytates inhibit the absorption of both iron and zinc, and zinc deficiency can have an adverse effect on intellectual performance. Third, lead can be consumed from the food supply or the environment. ID actually enhances the absorption of lead, and the lead toxicity may alter brain function. While ascorbic acid, phytates and lead all interact with iron and can also affect the brain, the author concludes that none of them are likely to be solely responsible for the relationship between ID and brain function. He concludes that the evidence still supports a direct link between iron status and brain activity.

Analysis, Brain, Cognition disorders, Cognitive disorders, Brain chemistry

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Behavioral effects of iron supplementation in infants in Madang, Papua New Guinea

Article Abstract:

Previous research has suggested that iron deficiency (ID) has an adverse effect on the cognitive or mental function and behavior of infants. More specifically, ID appears to reduce attention span. The authors evaluated whether supplementation with iron dextran affects attention span of infants in Papua New Guinea. In this region, many children are ill from both ID and malaria, an infectious disease caused by parasites in the blood. One-year-old infants were studied; 49 infants had received an injection of iron dextran at two months of age while the other 52 received a placebo (inactive) injection of water instead. The researchers measured the total fixation time (TFT) of the infants. TFT is the time in seconds that an infant looks at a visual stimulus or object. Infants with shorter TFT may be at nutritional risk, and longer TFT is thought to indicate better health. As expected, the iron- supplemented babies scored better on TFT than those in the placebo group. The authors concluded that children with adequate iron levels respond to and explore a visual stimulus to a greater extent than unsupplemented, and possibly iron deficient children. But these results were only found with infants who did not have malarial parasites. Children who tested positive for blood parasites scored the same whether they received iron or not; the authors could not readily explain this finding. Another measure of attention, called habituation, was not affected by iron supplementation. Habituation refers to the rate of change in attention to an object that is presented repeatedly. A limitation of this study is that researchers do not fully understand the underlying cognitive process that is measured by TFT.

Malaria, Papua New Guinea, Iron-dextran complex

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Methodologic issues in studying behavioral effects of infant iron-deficiency anemia

Article Abstract:

In iron-deficiency anemia (IDA) the red blood cells are not able to carry adequate amounts of oxygen to body tissues. IDA is a common nutritional disorder in many countries around the world. Previous research has linked IDA to adverse effects on human behavior, but it has been difficult to prove that IDA causes these effects. The author discusses a study of infants in Costa Rica with IDA. A total of 191 infants, aged 12 to 23 months, were tested for their mental and motor abilities. The tests were administered both one week and three months after the anemic infants began receiving supplements of elemental iron. Infants with IDA performed poorly on mental and motor test items compared to non-anemic infants, but elemental iron therapy did not result in higher scores for the majority of anemic infants. This suggests that some factor other than IDA might be causing or contributing to the lower scores. Conditions that foster nutritional deficiencies might also affect child development directly. The researchers did eliminate as many of these factors as possible, including family background, mother's intelligence quotient (IQ), infant growth and circumstances of the birth. In conclusion, anemic infants showed lower test scores, but iron therapy did not reverse this trend, which leaves the cause of the deficits uncertain.

Testing, Drug therapy, Costa Rica

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