DIETARY-INTAKE AND MICRONUTRIENT STATUS OF ADOLESCENTS - EFFECT OF VITAMIN AND TRACE-ELEMENT SUPPLEMENTATION ON INDEXES OF STATUS AND PERFORMANCE IN TESTS OF VERBAL AND NONVERBAL INTELLIGENCE

Relationships between micronutrient intake and status, and micronutrie nt status and performance in tests of intelligence mere investigated i n a group of adolescents (13-14 years old). Dietary intakes were asses sed using a 7 d weighed dietary record method, coupled with the collec tion of duplicate diets. Vitamin and trace mineral intakes calculated using food composition tables were compared with those obtained by dir ect analysis of duplicate diets. Micronutrient status was judged via a range of biochemical indices measured in blood samples taken after a 12-15 h fast. Blood samples were taken both before and after a 16-week period of vitamin and trace mineral supplementation. Individual tests of verbal and nonverbal intelligence, were also performed pre- and po st-supplementation. The results of this study indicate that the use of food table data may lead to substantial over- or underestimation of t he intake of several micronutrients. In general, the total calculated or analysed amount of a specific micronutrient consumed did not adequa tely predict status, as judged by a range of biochemical indices. Ther e were significant changes in status measurements over the 16-week stu dy period, irrespective of supplementation, and these changes were mar kedly influenced by the initial status of the subject. There was no ef fect of supplementation on performance in tests of intelligence. Howev er, there was a significant association between plasma ascorbic acid a nd initial non-verbal intelligence quotient (IQ) in the boys, and betw een whole blood glutathione peroxidase (EC 1.11.1.9) activity and non- verbal and verbal IQ in both sexes. These findings are discussed in re lation to other recent studies of the influence of micronutrient suppl ementation on the psychological performance of children.