An improvement in the iodine status of iodine deficient children, can have significant beneficial effects on mental performance, a new study suggests.

Researchers originally planned the study, to be double-blind, randomized, and placebo-controlled. However, the introduction of an adequate supply of iodized salt into the community caused a change in that design, as all children were getting increased iodine levels.

They studied a group of 196 initially iodine-deficient children, aged 7 to 11 years, in northern Benin.

The children's urinary iodine concentrations were measured and they were split into 2 groups:

• children with improved iodine status

• children with unchanged iodine status

Changes in mental and psychomotor performance were compared between the 2 groups.

Researchers found that the children with increased urinary iodine concentrations had a significantly greater increase in performance on the combination of mental tests than did the group with no change in urinary iodine concentrations.

The authors conclude that "An improvement in iodine status, rather than iodine status itself, determined mental performance in this population, which was initially iodine deficient. These findings suggest a "catch-up" effect in terms of mental performance."

American Journal of Clinical Nutrition November, 2000; 72: 1179-1185