Teenage boys who regularly eat fish may be doing their brains some good, a new study suggests.

Swedish researchers found that among nearly 5,000 15-year-old boys they surveyed, those who ate fish more than once per week tended to score higher on intelligence tests three years later.

The findings, published in the journal Acta Pediatrica, add to evidence that fish may indeed be brain food.

Researchers believe that the omega-3 fats found in fish — particularly oily fish like salmon, mackerel and, to a lesser extent, albacore tuna — are important to early brain development and to maintaining healthy brain function throughout life.

Past studies have found, for instance, that children whose mothers who ate fish regularly during pregnancy tend to have higher intelligence scores than their peers, and older fish-eaters have been shown to have a lower risk of cognitive impairment.

The new study appears to be the first large-scale one to look at the effects of fish on teenagers' intelligence, lead researcher Dr. Maria Aberg, of Goteborg University, told Reuters Health.

This is important, she explained, because the late-teens are a critical period for the brain "plasticity" that underlies intelligence and emotional and social behavior. Plasticity refers to the brain's ability to reorganize the connections among cells in response to normal experience, like learning a new skill, or to injury.

The findings are based on data from 4,792 male adolescents who completed detailed questionnaires on diet and lifestyle when they were 15 years old, then underwent standard intelligence tests when they were 18.

On average, Aberg's team found, those who ate fish more than once per week scored higher than those who ate fish less than weekly. This remained true when the researchers accounted for several other factors that influence both children's diets and their intelligence scores — like parents' education levels and the family's socioeconomic status.

"These findings are significant," Aberg said, "because the study was carried out between the ages of 15 and 18, when educational achievements can help to shape the rest of a young man's life."

It's too soon to make specific diet recommendations for teenagers, according to the researcher. "But for the time being," she said, "it appears that including fish in a diet can make a valuable contribution to cognitive performance in male teenagers."