Consuming seafood at least once every seven days improves youngsters' IQ scores by 4.8 points compared to those who never eat it, a study found today.
Frequently eating fish also makes children less likely to wake in the night, be tired during the day and resist going to bed, the research adds.
Study author Professor Adrian Raine from the University of Pennsylvania, said: "If fish improves sleep, great. If it also improves cognitive performance - like we've seen here - even better. It's a double hit."
Previous research reveals certain types of fish contain omega-3 fatty acids, which play a role in the growth and development of nerve tissue and may therefore boost intelligence.
These fatty acids also play a role in the production of the hormone melatonin, which regulates sleep and wakefulness.
How the research was carried out
The researchers analysed 541 Chinese students aged 12 years old.
Fish consumption between the ages of nine and 11 was determined via a questionnaire that asked the children how often they eat fish in a typical month. The questionnaire did not specify types of fish.
The children's sleep was measured by their parents completing a questionnaire that asked about the youngsters' hours of sleep a night, resistance at bedtime, sleep anxiety, night-time waking and daytime tiredness.
Their IQ was investigated by assessing their arithmetic, vocabulary and understanding of information, as well as their ability to arrange images and sort codes.
"Fish has really positive health benefits"
Results reveal children who frequently eat fish have significantly higher IQ scores and lower sleep disturbances.
Youngsters who eat fish at least once a week score up to 4.8 points higher on IQ tests than those who never eat seafood or do so less than once a month.
Children who eat fish two-to-three times a month score up to 3.31 points more.
Study author Dr Jennifer Pinto-Martin 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.
'Introducing the taste early makes it more palatable. Children are sensitive to smell. If they're not used to it, they may shy away from it.'
Professor Raine added: 'If fish improves sleep, great. If it also improves cognitive performance - like we've seen here - even better. It's a double hit.'
The researchers add children as young as 10 months could eat fish as long as it contains no bones and is chopped into small pieces. Fish should be part of youngsters' diets by two years old, they add.
The findings were published in the journal Scientific Reports.