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Prenatal DHA supplements don’t improve children’s IQ

Evidence shows it fails to bring benefits for children’s IQ by age 4 or age 7

Louise Prime

Wednesday, 22 March 2017

Strong evidence that prenatal supplementation with docosahexaenoic acid (DHA) fails to improve children’s IQ by the age of seven years has just emerged from long-term follow up of a randomised trial. The researchers behind the study,* which is published as a research letter in JAMA, said their findings call into question the increasing trend for women to buy DHA while pregnant in the belief that taking it is beneficial for their unborn baby’s neurodevelopment.

A group of researchers led from the South Australian Health and Medical Research Institute in Adelaide, Australia recruited pregnant women into their trial and then randomised them to take either 800mg DHA or placebo daily during the second half of their pregnancies. They followed up the women’s children and found that at the age of 18 months there was no difference between the DHA and placebo groups in terms of cognitive, language, and motor development.

When they tested the children again at four years old, the DHA supplementation group had no advantage over the placebo group in general intelligence, language, or executive functioning. However, they found a possible negative effect in the group exposed prenatally to DHA, for both parent-rated behaviour and executive functioning.

This follow-up study assessed intelligence quotient (IQ) once the children reached seven years old, which is the youngest age at which eventual adult performance can be indicated. Of all the eligible children originally included in the study, 543 (85%) participated in this seven-year follow-up assessment. There was no significant difference in average IQ between the DHA group (IQ 98.31) and control group (IQ 97.32). Furthermore, direct assessments of the children’s language, academic abilities and executive functioning revealed no significant differences between the two groups. The score for perceptual reasoning was slightly higher in the DHA group than in the control group – but also, again, the DHA supplementation group had worse parent-reported behavioural problems and executive dysfunction.

The study authors commented that the small but consistent negative effects of prenatal DHA supplementation on behaviour and executive functioning at both four and seven years old might reflect true effects – although they pointed out that effect sizes were small, and neurodevelopmental diagnoses did not differ between groups.

* Gould JF, Treyvaud K, Yelland LN, et al. Seven-year follow-up of children born to women in a randomized trial of prenatal DHA supplementation. JAMA 2017; 317(11): 1173-1175. doi:10.1001/jama.2016.21303.

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