Study suggests timing may be key in fish-asthma link

Among thousands of Dutch children included in a new study, those who first ate fish between the ages of six months and one year had a lower risk of developing asthma-like symptoms later on than babies introduced to fish before six months of age or after their first birthdays.

According to lead author Jessica Kiefte-de Jong, of the Erasmus Medical Center in Rotterdam, and her colleagues, one theory supported by the findings is that that early exposure to certain fatty acids in fish protects against the development of asthma.

The new results, based on more than 7,000 kids in The Netherlands, cannot prove that eating fish during a particular period in infancy prevented wheezing later on, but they add to other research that suggests a connection.

"The bottom line was that there is mixed evidence of whether the introduction of a seafood diet reduced the risk of asthma," said Dr. T. Bernard Kinane, chief of the pediatric pulmonary unit for MassGeneral Hospital for Children in Boston, who was not involved in the new study.

Concern over seafood allergies prompts some parents and doctors to delay introducing fish into babies' diets. However, some research has found that a mother's fish consumption during pregnancy, or the baby's consumption of it early on, may lower asthma risk.

To see whether the timing of a baby's first encounter with fish was linked to differences in asthma rates later in childhood, Kiefte-de Jong's team built on previous studies.

Using health and diet information from a group of 7,210 children born between 2002 and 2006 in Rotterdam, they found that 1,281 children ate fish in their first six months of life, 5,498 first ate fish in the next six months and 431 did not eat fish until after age one.

The researchers then looked at health records for when the children were about four years old, and how many parents reported that their kids were wheezing or short of breath.

Between 40 percent and 45 percent of parents of children who did not eat fish until after their first birthday said their kids wheezed, compared to 30 percent of kids who first ate fish when they were between six and 12 months old.

That, according to the researchers, works out to be about a 36 percent decreased risk of wheezing for the kids who first had fish between ages six months and one year.

Kids who first had fish before six months of age were at similar risk to those who were introduced to it after their first birthdays.

There was no significant association between the timing of fish introduction and shortness of breath.

"They found it was only protective between six and 12 months. That would make reasonable sense because that's when the immune system is getting educated," Kinane said.

He added that he was relieved the researchers also found no association between the amount of fish kids ate and their risk for asthma symptoms, which means that even a small amount of fish seems to be helpful.

"The reason I like that is that it reduces the risk of kids getting too much mercury," said Kinane.

Although Kinane said introducing children to fish between six and 12 months of age may be worth doing, he noted the possibility that there could be other explanations for the finding.

For instance, families who feed their children fish earlier and more often may be different in a variety of ways from those who do not.

"I thought it was an OK study, but I think it needs to be validated again," Kinane said.