Despite some evidence that taking fish oil pills during pregnancy can help children's brain development, a new study suggests that the supplements make no difference in measures of intellect when the kids are six years old.
The findings support the results of an earlier Norwegian study that also found no differences in IQ among seven-year-olds whose mothers did or did not take fish oil supplements while pregnant and breastfeeding.
Fatty acids, such as docosahexaenoic acid (DHA), that are found in fish and other foods are considered to be important for the developing fetus.
The question, however, has been whether adding more of these fats to mothers' diets through supplements will further benefit the baby.
In the current experiment, researchers asked expectant mothers during the second half of their pregnancies to take fish oil, fish oil plus a folate supplement, folate alone or a pill that did not contain any supplements.
Nearly seven years later, the team, led by Dr. Cristina Campoy at the University of Granada in Spain, gave intelligence tests to 154 children from this group.
The kids performed similarly on the tests, regardless of what type of pill their mothers had taken during pregnancy.
The results, published in the American Journal of Clinical Nutrition, do not mean that fatty acids like DHA are not important.
In fact, the researchers found that the children of women who had high levels of DHA in their red blood cells around the time they gave birth scored above average on the intelligence tests at age six.
These mothers, however, were not necessarily given fish oil supplements. Rather, the result could reflect mothers' intake of DHA from various sources over a longer period of time, and might mean that long term fatty acid intake "is more beneficial than receiving supplementation alone during pregnancy," the authors wrote in their study.
A recent study in Australia also found that DHA supplements did not help the visual development of babies.
The current study did not measure the diets of the children, something that could have influenced the results, said Dr. Ingrid Helland at Oslo University Hospital, who led the earlier Norwegian research.
"It might be that subtle beneficial effects of (prenatal fish oil) supplementation are being overshadowed by other factors (genetics, social stimulation, nutrition etc)," Helland wrote in an e-mail to Reuters Health.
She is not totally giving up on the idea that taking fish oil might be beneficial.
"If a friend would ask me if she should take supplements or not, I would recommend supplementation, but emphasize that we still do not have any scientific proof that it benefits the child," said Helland.