The research investigating supplementation with 800 mg of dietary docosahexaenoic acid (DHA) per day on more than 2,000 pregnant women, suggests that increased levels do not result in lower levels of postpartum depression in mothers or improved cognitive and language development in their offspring.
The authors of the study stated that their findings were “at odds with the results of some large-scale epidemiological studies” and warned that previous research may be inaccurate.
“It may be that even well conducted epidemiological studies overestimate effect size […] or that other nutrients in fish and seafood, beyond DHA, contribute to the observations from epidemiological studies,” wrote the researchers, led by Professor Maria Makrides, of the University of Adelaide
The finding has provoked debate from the dietary supplement sector, with Duffy MacKay, vice president of scientific & regulatory affairs for CRN stating: “A large body of scientific evidence has established a strong relationship between the DHA status of mothers and infants and a variety of important pregnancy-related outcomes, including infant development,”
“We must also remember that both depression and childhood development are impacted by many different variables and maintaining good nutrition is just one important preventive step mothers can take to achieve the best outcomes,” said Dr. MacKay.
Whilst, in a JAMA editorial accompanying the research paper, Dr. Emily Oken, an associate professor of medicine at Harvard Medical School pointed out that the research also provided further evidence that fish oil supplements “are safe, well tolerated, and reduce risks for early preterm birth, which is associated with poor neurocognitive outcomes and maternal depression.”
“Pregnant women should take care to get the recommended intake of 200 mg/d of DHA,” added Prof. Oken.
Fish oil benefits
Previous studies have shown increased intakes of omega-3 fatty acids during pregnancy are associated with a reduced risk of depressive symptoms in the postnatal period, as well as improved developmental outcomes in the offspring.
It is believed that DHA may be responsible for such associations; however the authors stated that, to date, trials investigating pregnancy and DHA have not been conclusive, “largely because of methodological limitations”.
They added that despite international recommendations that pregnant women increase DHA intakes, there is still uncertainty about its benefits for pregnant women and their children.
“Before DHA supplementation in pregnancy becomes widespread, it is important to know not only if there are benefits, but also of any risks for either the mother or child,” stated Prof. Makrides and colleagues.
The new study was designed to investigate the effects of increasing DHA during the last half of pregnancy, on levels of depressive symptoms in mothers and the cognitive development of their children.
The researchers observed no differences in the percentage of women reporting high levels of depressive symptoms during the first 6 months postpartum, between the DHA and control groups.
They also reported no differences in mean cognitive scores and mean language scores of children in the DHA group and the control group.
Fewer children in the DHA-treated group had delayed cognitive development compared with the control group. However, girls exposed to DHA had lower language scores and were more likely to have delayed language development than girls from the control group, which according to the authors “may highlight the sensitivity of girls to DHA intervention”
A blow for DHA?
The authors stated that their results “do not support routine DHA supplementation for pregnant women to reduce depressive symptoms or to improve cognitive or language outcomes in early childhood,” and warned that recommendations to increase DHA intake during pregnancy “are being implemented in the absence of well-designed, large-scale randomized controlled trials.”
Source: Journal of the American Medical Association (JAMA)
Volume 304, Issue15, doi: 10.1001/jama.2010.1507
“Effect of DHA Supplementation During Pregnancy on Maternal Depression and Neurodevelopment of Young Children: A Randomized Controlled Trial”
Authors: M. Makrides, R.A. Gibson, A.J. McPhee, L. Yelland, et al