Eating the right amount of fish: Inverted U-shape association between fish consumption and cognitive performance, and academic achievement in Dutch adolescents

Fish consumption has shown its benefits for cognitive functioning in the elderly or children with disorders (e.g,, autism, ADHD), but has rarely been investigated in relation to cognitive performance and school performance of healthy adolescents. Therefore an observational study in 700 Dutch high school students aged 12-18 years was executed. Fish consumption data, end term grades, scores on the Amsterdam Vocabulary Test, and scores on the Youth Self-Report were collected. Results revealed that 13.6% of the Dutch adolescents never ate fish, 6.4% met national guidelines, 16.9% reached half of the recommended amount, and 63.1% did eat fish but too little to meet at least half of the recommended amount. Analysis of variance, controlled for relevant covariates, showed significant differences between the four fish consumption groups in vocabulary (p= 0.05). A trend for significance was found for end term grades (p= 0.07). Contrast analyses demonstrated significant quadratic associations between fish consumption and vocabulary (p= 0.01) and end term grades (p= 0.01). Thus, our findings suggest that irrespective of sex, age, and educational track, the association between fish consumption and cognitive performance and academic achievement in adolescents consists of an inverted U-shape. Higher fish intake was associated with more advanced vocabulary and higher end term grades. However, eating more fish than the described recommended amount seemed no longer beneficial. The differences found between the groups (e.g. for academic performance) could be relevant for educational practice. The difference in z-score between the 1575-3150 mg fish group and the highest fish consumption group equals 0.23 points differences on a 10 point scale (Dutch grades are not given in letters, but in numbers between 0-10). This difference in fish consumption could therefore account for the difference between passing or failing.