NEW YORK (Reuters Health) – Zinc and iron deficiencies impair cognitive development, but nutritional supplements administered to under-nourished, preschool-aged children in Nepal did not appear to have any developmental benefit in a recent study.
“We were surprised because this is a population in which both iron and zinc deficiency is high, and we were hoping that giving supplements to children in their preschool years would have a positive impact,” Dr. Parul Christian, who led the study at Johns Hopkins Bloomberg School of Public Health, told Reuters Health.
Dr. Christian and her team published their results May 5 in Archives of Pediatrics and Adolescent Medicine.
They had randomly assigned 772 Nepalese children, ages 12 to 35 months, to four groups: 12.5 mg iron plus 50 mcg folic acid; or 10 mg zinc; or iron, folic acid and zinc; or placebo.
When the children were ages seven to nine years old, the researchers followed up with six tests of intellectual and motor skills, including the Movement Assessment Battery for Children and the Universal Nonverbal Intelligence Test, among others.
There was no significant difference between the supplement groups and the control group after adjusting for confounders such as gender, schooling, maternal literacy and diet.
Timing may be key for the supplements to have an effect and preschool age may be too late, the researchers say.
Children whose mothers took supplements while pregnant did have developmental gains by ages seven to nine, in a related study Dr. Christian and her team reported in 2010 in the Journal of the American Medical Association. (See Reuters Health story of Dec. 21, 2010.)
“That suggests there is a critical window of time during which such nutritional supplements may have a benefit. The prenatal period may be the time to provide nutritional supplements to moms for children,” Dr. Christian says.
The importance of understanding brain development and the nutrients needed at each stage “cannot be overstated,” wrote Dr. Sarah Cusick and Dr. Michael Georgieff at the University of Minnesota School of Medicine in Minneapolis, in an editorial.
These studies “emphasize that it is never too early to consider the effects of nutrients on brain development and that windows of opportunity for nutritional interventions in at-risk populations begin earlier than we conventionally think,” the reviewers wrote.
Arch Pediatr Adolesc Med 2012;166:404-410.