Eating fish makes children friendlier: Researchers say it’s the Omega-3, iodine and selenium content

One recent example is a University of Pennsylvania 2024 meta-analysis that found Omega-3 supplementing was able to “significantly reduce aggressive behavior.” Meanwhile, an earlier 2019 study found Omega-3 supplementing “fixed kids’ bad behavior.”

The researchers, who were examining social behavior rather than cognitive abilities, found children who ate the recommended amount of seafood (two servings weekly) showed better prosocial behavior than their peers. Prosocial behavior was considered to be helpfulness, sharing, and consideration to others.

The scientists found not eating any seafood already affected children at age seven, and increased over time when comparing their “social health” to children who ate recommended amounts.

Study details

Utilizing data from the Avon Longitudinal Study of Parents and Children (ALSPAC), the UK researchers examined nearly 8,300 children at age seven and more than 6,800 children at age nine. The goal of the researchers was to document if the amount of fish the children ate affected their thinking skills and behavior.

What they found was eye-opening: Children who ate no seafood at age seven had a 35% higher risk of poor prosocial behavior compared to children who ate at least 190 grams of seafood weekly (about two servings).

In the study intro the researchers expanded on what classified as prosocial behavior: It is what we see when children do things that help others—sharing their toys, helping someone who’s hurt, or comforting a sad friend.

These behaviors usually start to appear around a child’s first birthday and grow more complex as they age. They matter for both personal development and for getting along well in groups.

While previous studies have examined the nutrients in fish relative to cognitive abilities like IQ, in this case the researchers surmised that the nutrients contribute to brain development in ways that “specifically support social behavior rather than cognitive abilities.”

This effect lasted over time. By age nine, children who had eaten no seafood at age seven were 43% more likely to show poor prosocial behavior compared to those who had eaten the recommended amounts.

The beneficial nutrients

According to the study findings, fish is rich in nutrients that help brain development—especially docosahexaenoic acid (DHA) and eicosahexaenoic acid (EPA). These two omega-3 fatty acids are actually make up a large portion of brain cell membranes. They are concentrated in the brain and affect everything from gene expression to how flexible cell membranes are.

But seafood delivers other “brain nutrients” too. Iodine helps produce thyroid hormones that also affect brain development. Meanwhile, selenium helps make proteins for DNA production and works as an antioxidant.

Another lesser-known nutrient found in fish is choline. Choline helps produce acetylcholine, a brain chemical involved in pain response and thinking processes.

The challenge

While the researchers asserted an increase in children eating fish would be beneficial—not only for social development, but for other aspects of health—they acknowledged it would be a daunting task.

In Western countries fish is eaten in low amounts compared to beef, chicken and pork. According to the UK’s National Diet and Nutrition Survey, children aged four to 18 eat less than 20 grams of oily fish weekly. This is nowhere near the recommended 95 grams. Most Western countries show similar patterns of low seafood consumption—with Scandinavian countries being the exception.