According to findings published in the British Journal of Nutrition, data from 309 women receiving omega-3 supplements and 303 women on placebo showed no differences between the groups, but the quality of the available studies was described as “low-to-moderate”.
However, reviewers note that one of the studies involved in their meta-analysis did produce beneficial results, and that this occurred with relatively high daily doses of EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), said researchers from Leiden University in The Netherlands.
“[Results from this one study suggest] that a high dose of EPA may be important, but in this study, the intervention induced an increase in the erythrocyte DHA level but not in the EPA level,” they added. “Future studies should provide a complete profile of the oils used, and blood samples should be taken to evaluate the biochemical effects of the intervention.”
The systematic review and meta-analysis are a timely update on the state of the science. Numerous observational studies and uncontrolled trials have reported the benefits of fish oils and omega-3 fatty acids DHA and EPA on the behaviour and learning, especially in kids, as well for improving the symptoms of depression.
The number of studies reporting a potential beneficial effect from increased omega-3 fatty acid for depression is increasing. In the last couple of years, studies from various corners of the earth, including Norway (Journal of Affective Disorders), and England and Iran (Australian and New Zealand Journal of Psychiatry), have reported positive results.
Regarding depression in the general population, a review in the British Medical Journal's Drug and Therapeutics Bulletin (DTB) in February 2007 concluded that there is no solid scientific evidence to back the benefits reported by some observational studies and uncontrolled trials of fish oils and DHA and EPA on behaviour and learning as well as depression.
“Pregnancy and the post-partum period provide an excellent opportunity to examine the relationship between n-3 PUFA and depression,” state the Leiden-based researcher. “Pregnancy leads to several changes in PUFA status, including a depletion of maternal plasma DHA under normal dietary conditions that persists after delivery. This suggests that normal dietary intake may be insufficient during the perinatal period.
“During pregnancy, maternal DHA is selectively transferred to the fetus to support optimal fetal development, and after birth, breast milk provides DHA to the infant. Mothers may be at higher risk for post-partum depression when they become depleted of n-3 PUFA, and especially of DHA,” they added.
Reviewing the review
The reviewers identified seven randomised controlled trials for their meta-analysis, involving 309 women receiving EPA and/or DHA supplementation, and 303 women on placebo.
In general, the supplements were not associated with a significant improvement in depression measures. “In a subgroup analysis of three small studies of pregnant women with major depression, there was some indication of effectiveness,” they added.
“It is unclear whether DHA or EPA or their combination may be more effective,” wrote the authors. “The positive study used 2.2 g EPA and 1.2 g DHA daily, suggesting that a high dose of EPA may be important, but in this study, the intervention induced an increase in the erythrocyte DHA level but not in the EPA level.
“Future studies should provide a complete profile of the oils used, and blood samples should be taken to evaluate the biochemical effects of the intervention. The intervention should be sufficient in dose and duration, and should start when the natural decline in n-3 PUFA during pregnancy occurs,” they added.
“On the basis of these findings, EPA and/or DHA cannot be considered to be an empirically supported treatment for perinatal depression as yet,” wrote the scientists. “However, the limitations in study quality complicate this interpretation.
“Well-controlled and larger studies of longer duration are necessary to assess the efficacy of the DHA and EPA in pregnant patients with a major depressive disorder or at high risk for developing depression (e.g. with a history of depression),” they concluded.
Source: British Journal of Nutrition
Published online ahead of print, FirstView Articles, doi: 10.1017/S0007114510004125
“The efficacy of n-3 fatty acids DHA and EPA (fish oil) for perinatal depression”
Linda A. W. Jans, Erik J. Giltay and A. J. Willem Van der Does
The full paper can be accessed here.