n3 Fatty Acid Intakes Are Inversely Related to Elevated Depressive Symptoms among United States Women

Evidence that depressive symptoms are inversely related to n3 fatty acids is growing among United States adults.  We assessed whether self reported depressive symptoms were inversely associated with n3 fatty acid intakes by using a cross to sectional study in 1746 adults (aged 30 to 65 y) in Baltimore City, MD (2004 to 2009). The 20 item Center for Epidemiologic Studies Depression Scale (CES  D) was used, with a CES D score 16 suggestive of elevated depressive symptoms (EDS). By using the mean of two 24 h dietary recalls, n3 highly unsaturated fatty acids (HUFAs; 20 carbons),  n3 polyunsaturated fatty acids (PUFAs; 18 carbons), and plausible ratios with n6 fatty acids were estimated. EDS prevalence was 18.1 percent among men and 25.6 percent among women. In women, the uppermost tertile (tertile 3) of n3 PUFAs (compared with tertile 1) was associated with reduced odds of EDS by 49 percent, with a substantial sex differential. The n3 PUFA to n6:PUFA ratio was inversely related to EDS among women (tertile 2 vs. tertile 1, OR: 0.74; 95 percent CI: 0.41, 1.32; tertile 3 vs. tertile 1, OR: 0.47; 95 percent CI: 0.27, 0.83). A similar pattern was noted for n3 HUFA to n6 HUFA among women.  For CES D subscales, n3 PUFA (percent of energy) was inversely related to somatic complaints, whereas positive affect was directly related to n3 HUFA (percent of energy; total population and among women), n3 HUFA to n6 HUFA (women), and n3 HUFA to n6 PUFA (total population and among women). In sum, among United States women, higher intakes of n–3 fatty acids [absolute (n3) and relative to n6 fatty acids] were associated with lower risk of elevated depressive symptoms, specifically in domains of somatic complaints (mainly n3 PUFAs) and positive affect (mainly n3 HUFAs). (Authors abstract)

There is evidence for a relation between n3 fatty acids and depressive symptoms as lower intake of n3 fatty acids (reflected in self to reported intakes and/or in plasma or erythrocyte concentrations) was associated with higher risk of depression or elevated depressive symptoms (EDS). The influence of dietary factors and their over to time patterns of change, particularly n3 fatty acid intake, has gained attention over the past decade. During the last century, per capita consumption of soybean oil, rich in LA, increased 1000 to fold. This increased the availability of LA from 2.8 percent to 7.2 percent of energy, whereas the availability of ALA increased only from 0.39 percent to 0.72 percent of energy and was accompanied by declines in n3 HUFA intakes.  The predicted net effects included declines in tissue n3 HUFA status from 36.8 percent to 22.9 percent, primarily due to greater intakes of LA over the century. This is in sharp contrast to the diets in regions of hominid evolution, which were higher in n3 HUFAs (2.26 to 17.0 g/d) and lower in LA (range: 2.3 to 3.6 percent of energy). Recent research suggests that the imbalance between those 2 classes of fatty acids, specifically deficient intakes of EPA and DHA and high concentrations of the highly unsaturated n6 fatty acid arachidonic acid (AA; 20:4n6) in tissues, may contribute to the rising burden of many chronic conditions, including cardiovascular disease and certain types of cancer, in addition to cognitive decline. The aim of the present study was to assess whether self reported depressive symptoms (and related domains), measured by the Center for Epidemiologic Studies Depression Scale (CESD)
in a sample of 1746 adults residing in Baltimore City, MD, were associated with intakes of n3 fatty acids (measured with two 24 to h recalls), both in absolute terms and relative to n6 fatty
acids.
This study is one of very few large population surveys and among the first conducted in United States adults to show a substantial association between n3 fatty acids (absolute and relative to n6 fatty acids) and self to reported depressive symptoms (and their components). The findings generally supported the hypothesis that both n3 HUFA and n3 PUFA intakes as well as their related ratios are linked to lower amounts of depressive symptoms. The observed association was substantial and stronger only among women and remained substantial after controlling for many of the sociodemographic, lifestyle, and health to related potential confounders, including dietary intakes of specific nutrients. One domain of the CES D, namely positive affect, was more sensitive to n3 HUFA exposures than others among women. In contrast, also among women, somatic complaints were mostly linked to n3 PUFA intakes. It is worth noting that among HANDLS study participants, fish was the major contributor of DHA and and that DHA and EPA (percent of energy) was adequate at the 0.15 percent cutoff only in 17.2 percent of women and 13.3 percent of men. The study found that the putative protective effect of n3 fatty acids on depressive outcomes was restricted to women. This could either be due to differences in sample size between men and women (n of 755 men and n of 991 women).

In summary, the relationship between n3 fatty acids and depression has been examined in a limited number of observational and experimental studies. Additional prospective observational
studies are needed to strengthen evidence of a causal association in the hypothesized direction. This should possibly include supplemental n3 fatty acid intakes in addition to their main dietary source as well as a biomarker for intake of n3 fatty acids, while considering the balance of n3 to n6 fatty acids.  The study findings support the hypothesis of a protective effect of n3 fatty acids, both HUFAs and PUFAs, against depressive symptoms, particularly among women. Whereas reverse causality cannot be ruled out, it is more likely that reduced concentrations
of n3 fatty acids may contribute to symptoms of depression, and not vice to versa. (Editors comments)