New US research suggests that children who eat fish just once a week could benefit from better sleep and have higher IQ scores than those who eat fish less frequently or not at all.
Carried out by the University of Pennsylvania, the research follows previous studies which have already found a relationship between omega-3s (the fatty acids found in many types of fish) and improved intelligence, and omega-3s and better sleep.
However, the three have not been connected together until now.
"This area of research is not well-developed. It's emerging," explained Jianghong Liu, lead author on the paper, "Here we look at omega-3s coming from our food instead of from supplements."
For the new study the team looked at a cohort of 541 9- to 11-year-olds in China and asked the children to report how often they had consumed fish in the past month, with options ranging from often (at least once per week), to sometimes (2-3 times per month), to seldom or never (less than 2 times per month).
The children were asked to take an IQ test, which examines verbal and non-verbal skills such as vocabulary and coding.
The researchers also asked parents to complete a questionnaire about their children's sleep, including questions on sleep duration and frequency of night waking or daytime sleepiness.
After taking into account factors such as parents' education, occupation, marital status, and the number of children in the home, the team found that children who reported eating fish at least once a week scored 4.8 points higher on the IQ exams than those who said they "seldom" or "never" ate fish.
Those who sometimes ate fish scored 3.3 points higher.
In addition, the team found that those who had a higher consumption of fish also had fewer sleep disturbances, indicating better quality sleep overall.
"Lack of sleep is associated with antisocial behavior; poor cognition is associated with antisocial behavior," said co-author Professor Adrian Raine. "We have found that omega-3 supplements reduce antisocial behavior, so it's not too surprising that fish is behind this."
"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," added one of the study's co-authors Jennifer Pinto-Martin. "Children should be introduced to it early on."
The team note that fish should be introduced into children's diets by age 2, but even children as young as 10 months can consume fish as long as it has no bones and has been finely chopped.
"Introducing the taste early makes it more palatable," Pinto-Martin explained. "It really has to be a concerted effort, especially in a culture where fish is not as commonly served or smelled. Children are sensitive to smell. If they're not used to it, they may shy away from it."
The team also advise the whole family to increase their fish consumption together, little by little, even to just once per week.
"Doing that could be a lot easier than nudging children about going to bed," Raine said. "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 results can be found published online in Scientific Reports, a Nature journal.