Fish oil supplements failed to ward off depression in pregnant women after delivery or bolster their infants’ cognitive and language development, an Australian study found.
About 9.7 percent of women taking the supplements in the study reported high levels of depression symptoms in the six months after delivery, said Maria Makrides, the lead author of the research, published today in the Journal of the American Medical Association. That compared with 11.2 percent for women taking vegetable oil capsules, meaning the difference was “nonsignificant,” according to the research.
The study is the largest to look at what happens in pregnant women who take fish oil supplements rich in dietary docosahexaenoic acid, or DHA, Makrides said in an e-mail on Oct. 17. Healthy women with normal pregnancies may not need DHA supplements, she said, citing the study data.
“We obviously undertook the trial expecting to find a positive result,” said Makrides, deputy director of the Women’s & Children’s Health Research Institute and professor of human nutrition at the University of Adelaide in Australia. “The fact that we essentially found no effect was a surprise.”
Further work is needed to determine the potential benefits of DHA supplementation for women with a history of depression and for women at risk of having a premature baby, she said.
Emily Oken, an associate professor of population medicine at Harvard Medical School and Harvard Pilgrim Health Care in Boston, who wrote an accompanying editorial in the journal, said pregnant women shouldn’t give up eating low-mercury fish or taking recommended doses of fish oil, as the mineral does help prevent preterm labor and may have benefits not shown in the study.
“It’s a little disappointing that the evidence isn’t convincing,” Oken said in a telephone interview on Oct. 15. “It’s a little early to say that there’s no benefit.”
Scientists are unsure exactly how DHA works, Oken said. DHA is a building block in the brain and eyes and may influence how they develop, she said.
Researchers in the trial studied 2,399 women at five Australian hospitals who were recruited from October 2005 to January 2008. The mothers-to-be received 800 milligrams a day of DHA in fish oil or were given vegetable oil capsules, which act like a placebo, from the time they entered the study until the birth of their children.
The researchers followed 726 of the children through December 2009 and assessed them at 18 months for abilities including memory, problem solving and vocabulary.
They found that the percentage difference between groups in terms of postpartum depression six months after delivery was nonsignificant. The study showed a reduction in depression symptoms in a subgroup of women who took DHA and had a previous history of depression, Makrides said. More studies are needed to confirm that finding, she said.
While fewer women taking DHA went into early labor compared with the vegetable oil group, the DHA group had a higher risk of going past the due date for births and requiring either inductions or caesarian sections, Makrides said. Treating 100 women with DHA would prevent one preterm birth of less than 34 weeks and create two post-term inductions or caesarean sections, she said.
“Clearly these tradeoffs are important to consider and it may be that DHA supplementation may be most useful to women at risk of having a preterm baby,” Makrides said.
Researchers also are planning a follow-up report on the children when they reach 4 years old, she said.
Current recommendations say pregnant women should consume 200 milligrams a day of DHA through fish or dietary supplements, said Elizabeth Poynor, a gynecologist at Lenox Hill Hospital in New York, who wasn’t involved in the study.
The lack of benefit in today’s findings may be because the women took a supplement rather than obtained the nutrient from natural sources, she said.
“We can’t assume that what comes in supplement form has the same activity as what we have in dietary form,” Poynor said in a telephone interview on Oct. 15.