Studies have looked at the impact of omega-3 intake on various populations and suggested that fish intake during pregnancy has a positive impact on the neurodevelopment of infants and that they reduce the risk of impaired thinking and reasoning functions in the middle-aged and elderly populations. Dietary deficiency of omega-3 fatty acids has been shown to be associated with depression and schizophrenia.
The omega-3 compounds may also improve the brain's metabolism and use of energy sources and so reduce biochemical stress on the working brain cells.
Explanations for these beneficial effects focus on the impact that the omega-3 compounds have on the brain. As important components of the membranes of the cells that comprise the brain, they may influence the development of brain cells and their ability to connect to each other. They may also help in developing new nerve pathways when existing pathways are impaired. The omega-3 compounds may also improve the brain's metabolism and use of energy sources and so reduce biochemical stress on the working brain cells.
In a new study, published in the March issue of Acta Pediatrica, researchers in Sweden investigated the effects of omega-3 fatty acids on a population not previously studied, adolescents. In Sweden, final grades in high school are used to guide students into their future educational and professional choices. The investigators reasoned that if there were a positive effect on the development of thinking and reasoning functions of the brains during the teenage years, the choices made by Swedish teens for university and subsequent professions might be positively impacted.
They performed a longitudinal population study on several thousand teenage boys that began with a questionnaire survey at age 15, and ended with a follow-up of the same adolescents when they entered the army at 18. They felt that eating habits at age 15 were likely to be reflective of long-term family patterns.
At age 15 the 4792 adolescent boys completed an extensive questionnaire with their parents that included information about fish consumption, and information about potential confounding influences on cognitive/intellectual development. These included socioeconomic variables such as parental education, rural vs. urban living, and body mass index.
Fish intake was characterized as more than once/week (20.2% of responders), about once/week (56.6% of responders) and less than once/week (22.7%). Fearing inaccurate responses, the researchers did not ask about smoking and alcohol use. However, anonymous questionnaires completed by teens from that region reflected less than 1.5% of males regularly over-consumed alcohol.
This same group of teens who were questioned at 15 years, entered mandatory military service at age 18 and underwent the routine IQ testing administered to all entering youth. There were 10 subtests, four of logic, two verbal tests of synonyms and one of opposites, two tests of visuospatial geometric perception, one of technical mechanical skills that included math and physics problems. The results were combined into three scores, an overall, or global IQ score, a visuospatial (ability to work with three dimensional concepts) score, and a verbal score. Of the original cohort of 4792, test results were available for comparison for 3971 students.
The researchers compared the results of the IQ tests to the records of fish consumption, using statistical methods to remove the effects of potentially confounding variables. They found a strong positive association between the amount of fish a boy ate and his combined IQ score, as well as the separate verbal and visuospatial scores. Statistically, the impact of fish consumption was the same for all three IQ measures. The scores were independent of parents' educational achievement — they were not different if the parental educational level was only through high school, or continued through university.
These results are significant, but the researchers note that further and expanded research will add to their data. Their questionnaires did not ask about vegetable intake, which is known to positively impact cognition. Nor did they ask about the total diet and total caloric intake. They also did not distinguish between fatty and less fatty fish, although omega-3 fatty acids are more plentiful in fatty fish.
However, this research is compelling, both in its results, and the fact that the positive findings are consistent with other recent studies and current knowledge about the impact of omega-3 fatty acids on brain function. The researchers hope that this study, in conjunction with others will lead to some beneficial nutritional recommendations.
It should be noted that there has been concern about the safety of consumption of fatty fish because they have been found to contain environmental toxins (chiefly mercury) that are harmful to the human body and particularly to the developing fetus. There has also been concern about lack of standardization of fish oil supplements, as well as the potential for contaminants in the supplements themselves, depending on their source. Individuals considering increasing their omega-3 fatty acid intake should work with their doctors, or consult with a nutritionist, for safe sources, recommended portions, and to learn of the potential side effects.