The findings show that youngsters who eat fish once a week score at least four points higher than average in IQ tests, compared with those who do not eat fish at all or consume it less frequently.
The research team from the University of Pennsylvania asked 541 pupils in China, aged between nine and 11, to fill in a questionnaire about how often they consumed fish, which is rich in omega-3 fatty acids, in the past month.
The students also took the Wechsler Intelligence Scale for Children-Revised test – which is the Chinese version of an IQ exam.
Their parents were asked about the children’s sleep quality, which included duration, how frequently they woke up during the night and daytime sleepiness.
The team found that children who reported eating fish weekly scored 4.8 points higher in the IQ tests than those who said they “seldom” or “never” ate fish.
In addition, fish consumption was found to be associated with fewer sleep disturbances and, consequently, better sleep quality.
Jennifer Pinto-Martin, executive director of Penn’s Centre for Public Health Initiatives, said: “It adds to the growing body of evidence showing that fish consumption has really positive health benefits and should be something more heavily advertised and promoted.
“Children should be introduced to it early on. It really has to be a concerted effort, especially in a culture where fish is not as commonly served or smelled.”
She added: “Children are sensitive to smell. If they’re not used to it, they may shy away from it.”
Professor Adrian Raine, of Penn’s Perelman School of Medicine, said: “Lack of sleep is associated with an anti-social behavior; poor cognition is associated with anti-social behavior.
We have found that omega-3 supplements reduce anti-social behavior, so it’s not too surprising that fish is behind this.
“If the fish improves sleep, great. If it also improves cognitive performance – like we’ve seen here – even better. It’s a double hit.”
The research is published in Scientific Reports.