American women with higher blood levels of omega-3 fatty acids have a 49% reduction in risk of elevated depressive symptoms, a result that has been hailed as ‘timely’ by a leading industry expert.
A substantial difference was observed between the sexes with no significant effects observed in men, which could be due to a sex-specific biological influence, according to researchers from the National Institutes of Health (NIH), the University of Delaware, and Eastern Virginia Medical School.
“Our study findings support the hypothesis of a protective effect of n–3 fatty acids, both [n–3 highly unsaturated fatty acids (HUFAs; at least 20 carbons), n–3 polyunsaturated fatty acids (PUFAs; at least 18 carbons)], against depressive symptoms, particularly among women,” they wrote in the Journal of Nutrition .
“Whereas reverse causality cannot be ruled out, it is more likely that reduced concentrations of n–3 fatty acids may contribute to symptoms of depression, and not vice-versa.
“Thus, these findings support the need for Dietary Reference Intake recommendations in the US, particularly for DHA and EPA (i.e., n–3 HUFAs), given their strong impact on depressive symptoms, particularly the domain of positive affect.”
Omega-3s: A high priority topic
Commenting on the results, Harry Rice, PhD, VP of regulatory & scientific affairs for the Global Organization for EPA and DHA Omega-3s (GOED), told NutraIngredients-USA: “It's worth noting that from the first meeting of the Dietary Guidelines Committee (DGAC), omega-3s (EPA & DHA) were declared as a high priority topic. Given that the DGAC is interested in mental health, and the second meeting of the DGAC will convene at the beginning of October, this publication is timely.”
“Results from this well-designed and conducted study corroborate the hypothesis that the long-chain n-3 PUFAS, EPA & DHA, offer protection against depression, with reduced concentrations of EPA & DHA contributing to symptoms of depression. While additional studies are necessary to verify a cause and effect relationship, the authors rightfully acknowledged this,” added Dr Rice.
Led by May Beydoun, PhD, from the National Institute on Aging, the researchers assessed if there was an association between omega-3 intakes and symptoms of depression using the 20-item Center for Epidemiologic Studies–Depression Scale (CES-D) in 1,746 adults aged between 30 and 65.
The data showed that elevated depressive symptoms (EDS) were prevalent in 25.6% of women, and 18.1% of men. Adequate intakes of linoleic acid (LA) and alpha-linolenic acid (ALA) were observed in 43 to 59% of men and women. However, significantly fewer men and women achieved adequate intakes of EPA and DHA ranged from 5.2 and 17.2%.
Further crunching of the numbers showed that the highest intakes of omega-3 PUFAs was associated with a significant 49% reduction in the risk of elevated depressive symptoms in women. A similar result was obtained for the ratio of omega-3 HUFA to omega-6 HUFA in women, they added.
Dr Beydoun and her co-workers proposed three mechanisms to explain the associations. The first involves the serotonergic neurotransmitter system (3,68), which is known to be regulated by omega-3s. The second is called the ‘macrophage theory of depression’, and is related to inflammatory responses. Omega-3s are known to promote the formation of anti-inflammatory compounds, while omega-6s promote proinflammatory eicosanoids, which can cause psychiatric disturbances and emulate symptoms of depression. The third mechanism involves “impaired phospholipid metabolism and impaired fatty acid–related signal transduction in the etiology of both depression and bipolar disorder and attempts to link depression to cardiovascular and autoimmune disease through these metabolic impairments”, they said.
“Additional prospective observational studies are needed to strengthen evidence of a causal association in the hypothesized direction,” wrote Dr Beydoun and her co-workers. “This should possibly include supplemental n–3 fatty acid intakes in addition to their main dietary source as well as a biomarker for intake of n–3 fatty acids, while considering the balance of n–3 to n–6 fatty acids.”
Source: Journal of Nutrition
Published online ahead of print, doi:10.3945/jn.113.179119
“Omega-3 Fatty Acid Intakes Are Inversely Related to Elevated Depressive Symptoms among United States Women”
Authors: M.A. Beydoun, M.T. Fanelli Kuczmarski, H.A. Beydoun, J.R. Hibbeln, M.K. Evans, A.B. Zonderman