In their main analysis, researchers found no significant cognitive benefits in Norwegian preschool students fed a fatty fish lunch versus a non-fish meat lunch for 16 weeks; however, they detected slight benefits in a sub-analysis adjusted for dietary compliance.
In a new study1 published in BMC Medicine, researchers set out to study whether fatty fish intake may produce brain-health benefits in Norwegian preschool children aged 4 to 6 years old. In their main analysis, researchers found no significant cognitive benefits in Norwegian preschool students fed a fatty fish lunch versus a non-fish meat lunch for 16 weeks; however, they detected slight benefits in a sub-analysis adjusted for dietary compliance.
Researchers say that although omega-3 intake has previously been studied for effects on cognitive development in infants, no other evidence currently exists for a similar effect in later childhood. Thus, in this study, the researchers sought to explore whether increased fatty fish consumption could exert these cognitive-health benefits in preschool children. “To our knowledge, this is the first RCT involving fatty fish consumption and cognitive function in preschool children, and other studies are thus not directly comparable,” they wrote.
The two-armed, randomized, controlled trial included 218 children from 13 kindergartens in Norway. Researchers served 105 of those children lunch meals with either fatty fish (herring and mackerel) or non-fish meat (chicken, lamb, or beef) three times per week for a total of 16 weeks.
In order to assess what effects, if any, increased intake of fatty fish had on children’s cognitive health, researchers utilized the Wechsler Preschool and Primary Scale of Intelligence, third edition (WPPSI-III), a test designed to test general intellectual abilities. Researchers also assessed subjects’ fine-motor coordination (for both dominant and non-dominant hand) using the 9-Hole Peg Test and pre-and post-intervention.
The children’s caregivers were also instructed to complete a food frequency questionnaire, which was used to judge whether the subjects were adhering to Norwegian dietary recommendations outside of the intervention meal. According to researchers, “The recommendations used included the following: eat at least three portions of vegetables and two portions of fruit every day, eat at least four whole-grain products every day, eat fish corresponding to two to three dinner servings a week, limit the intake of red meat products, choose low-fat dairy products, limit the intake of added sugar, choose water as the recommended beverage, and do some form of physical activity at least 30 min every day.”
At the end of the study period, there were no differences in change in the WPPSI-III raw scores from pre- to post-intervention between the fish and non-fish groups. However, in the 9-Hole Peg Test, children in the fish group demonstrated a slight improvement in performance when using their non-dominant hand compared with the meat group. (“The positive effect of the intervention in the 9-HPT non-dominant hand should be interpreted with care, given that we did not find a beneficial effect on the dominant hand,” the researchers cautioned.)
In a further sub-analysis, researchers did detect slightly better improvement in the WPPSI-III scores in the fish versus non-fish group, after adjusting for dietary compliance. In some of the sub-tests, including vocabulary, block design, and symbol search, fatty fish consumption improved cognitive performance. Improvements in the 9-Hole Peg Test non-dominant hand also remained stronger in the fish group, compared with the meat group.
The researchers concluded that while “no significant effects of serving fatty fish were found on cognitive functioning measured by WPPSI-III in the main analyses,” in the sub-analyses an increased intake of fatty fish did appear to exert a beneficial effect on cognition, when taking the amount of fish or meat the children consumed into account.
Regarding the overall largely neutral results, they posited that perhaps results could be more dramatically positive in subjects with less-than-adequate nutrition, as the current subjects’ overall seafood intake (outside of the study meal) “was relatively high.” In fact, almost 50% of the children consumed seafood according to the recommendation of two to three times weekly, they said. “Thus, a possible explanation for the lack of an effect of fatty fish in the main analyses in the present trial could be that the children were not deficient in micro- or macronutrients prior to the intervention,” they said.
Finally, they said, a longer study period might be beneficial. “Although the four-month intervention period was sufficient to yield an increase in the children’s [red blood cell] marine fatty acids, it may take longer until this increase leads to improvements of complex cognitive abilities,” they said.
1. Ãyen J et al., “Fatty fish intake and cognitive function: FINS-KIDS, a randomized controlled trial in preschool children,” BMC Medicine. Published online March 12, 2018.