May 4, 2007

     Volume 2007, No. 4

This free electronic newsletter for nutrition and health professional subscribers is brought to you by The Beef Checkoff through the National Cattlemen’s Beef Association. See the end of the newsletter for communication and subscription information.

Please visit our Web site at http://www.beefnutrition.org/ for information and education materials about nutrition and health.

IN THIS EDITION

FURTHER STUDIES NEEDED ON THE EFFECTS OF IRON DEFICIENCY WITH AND WITHOUT ANEMIA ON COGNITION AND BEHAVIOR

NEW DATA ANALYSIS FROM WHAT WE EAT IN AMERICA, NHANES 2001-2002 RELEASED ON THE FOOD SURVEYS RESEARCH GROUP WEBSITE

FURTHER STUDIES NEEDED ON THE EFFECTS OF IRON DEFICIENCY WITH AND WITHOUT ANEMIA ON COGNITION AND BEHAVIOR

Iron deficiency (ID) is a critical health issue with 2 billion women and children iron deficient worldwide.  In the United States, the greatest prevalence of ID, both with and without anemia (ID+A, ID-A), is among adolescent girls (9-16%) and children during the brain growth spurt (7%). This review in the April issue of the American Journal of Clinical Nutrition demonstrates that further studies are needed to understand the causal relationship between dietary ID +/- A and cognitive and behavioral functioning.  Because a relationship between any micronutrient deficiency and brain function can have major public health implications, both animal and human studies on the effects of ID are warranted.

Reviewers agree that there is a consistent correlation between ID+A and poor cognitive and behavior performance of children.  However, it cannot be excluded that the study results are confounded by unaccounted socioeconomic factors and the generalized effects of anemia on physical energy. A critical question being addressed by current research is the time length of the effects of ID+A on cognitive or behavioral functioning. The reviewers found that the poor test performance of children more than 2-years old tended to improve with iron treatment, but was resistant to change in children less than 2 years of age.  This finding is supported by several long-term follow-up studies. 

Few studies have focused on the effects of ID-A on cognition and behavior.  Reviewers looked at both human and animal studies and suggest that this question remains unresolved.  Some studies support a relationship between poor behavioral and cognitive function and ID, particularly when the deficiency occurs during critical stages of development.  Two important considerations that need clarification are the association between dietary iron deficiency and functional brain iron and the availability of stored brain iron to different regions of the brain during iron-restrictive periods.

Though evidence suggests the association, the reviewers conclude that it is premature to identify a causal relationship between ID during development and subsequent cognitive or behavioral performance. They suggest additional research in the following areas:

• critical periods of development sensitive to ID

• regional difference in brain sensitivity to ID

• ID effects in high-risk persons

• effects of maternal ID on pregnancy outcome

• ID effects in persons with multiple deficiencies

• uncertainties in extrapolating results from animals to humans

• ID effects in longitudinal and long-term follow-up studies and in studies of sufficient statistical power to determine weak but possibly meaningful relationships.

Citation:

An overview of evidence for a causal relation between iron deficiency during development and deficits in cognitive or behavioral function. McCann JC, Ames BN. The American Journal of Clinical Nutrition, 2007;85:931-45.

Do you have any comments or suggestions? Send an e-mail to umaileditor@beef.org.

©  Cattlemen's Beef Board and the National Cattlemen’s Beef Association.
     All rights reserved.