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Fish-oil supplements don't appear to help pregnant women prevent post-partum depression or boost the baby's brain development as previously believed, according to a large trial published Tuesday in the Journal of the American Medical Association.
The 2,400-woman, randomized study complicates the advice for pregnant women. It adds to a body of mixed research on some potential benefits of the popular omega-3 fatty acid known as DHA, or docosahexaenoic acid. DHA, which can move from the mother to the baby during pregnancy, accumulates in the brain and is thought to be involved in helping brain cells communicate.
In general, for healthy women with normal pregnancies, '[DHA] supplementation will actually not give you a huge benefit in terms of neurodevelopmental outcomes and reducing depressive symptoms,' said Maria Makrides, an author on the study and deputy director of the Women's and Children's Health Research Institute in North Adelaide, Australia.
The results are 'disappointing,' said Emily Oken, a professor of population medicine at Harvard Medical School and Harvard Pilgrim Health Care Institute, who wrote an editorial to accompany the paper but wasn't involved in the study. But 'it doesn't mean we should give up on fish or fish oil during pregnancy,' she said.
Several previous studies have shown that eating fish during pregnancy helped in the baby's brain development and in reducing the risk of post-partum depression. That research, however, typically didn't involve randomized, controlled studies. Instead, women were asked whether or not they chose to eat fish during pregnancy.
It could be the case that eating fish is better than taking fish-oil supplements or that women who opt to eat fish are generally healthier and engage in other health-promoting behaviors, Dr. Oken said. The few trials conducted that separated participants, into a group taking fish-oil supplements and another that didn't, weren't well done, because the women often knew if they were getting the supplement, and in some cases there wasn't a comparison group at all, she said.
The latest study does suggest that some subgroups of women might benefit from fish-oil supplements. For instance, those with a history of clinical depression -- and thus are at higher risk of post-partum depression -- who took 800 milligrams of fish oil daily lowered their risk of getting depressed after the birth by about 4% compared with those who didn't take fish oil.
However, the difference wasn't statistically significant because of the small number of women in the study who had been previously depressed, said Dr. Makrides, who is also a professor of human nutrition at the University of Adelaide.
Women in the fish-oil group had lower rates of pre-term births, particularly births earlier than 34 weeks of gestation. But, there was a trade-off: More women who took the supplement needed their labor to be induced or had caesarean sections because the babies stayed in the womb longer, said Dr. Makrides.
Additional research is needed to study the benefits of targeting DHA supplements to women with a history of depression or who previously had a premature baby, according to Dr. Makrides. However, all pregnant women should strive for balance and eat a variety of foods, including fish, she said.
Omega-3 fatty acids are the fourth most common supplement after multivitamins, calcium and vitamin C, according to the Council for Responsible Nutrition, an industry trade group.
Other health benefits have been attributed to omega-3s. Research suggests they lower triglyceride fat levels and are likely helpful in preventing heart disease, according to the National Institutes of Health. There is some evidence omega-3s also may help decrease blood pressure, improve thinking in kids with attention deficit-hyperactivity disorder, help with weight loss and reduce the risk of endometrial cancer. Fish oil doesn't seem to help lower blood sugar for diabetics, however, and there isn't enough research to conclude effectiveness for conditions such as Alzheimer's disease, irregular heart beat and cancer, according to the NIH. 2010-11-08
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