The omega-3 index is inversely associated with depressive symptoms among individuals with elevated oxidative stress biomarkers

Authors: BIGORNIA, SHERMAN - University Of Massachusetts; HARRIS, WILLIAM - University Of South Dakota; FALCON, LUIS - University Of Massachusetts; ORDOVAS, JOSE - Jean Mayer Human Nutrition Research Center On Aging At Tufts University; Lai, Chao Qiang; TUCKER, KATHERINE - University Of Massachusetts

Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/19/2016
Publication Date: 3/2/2016
Citation: Bigornia, S.J., Harris, W.S., Falcon, L.M., Ordovas, J.M., Lai, C., Tucker, K.L. 2016. The omega-3 index is inversely associated with depressive symptoms among individuals with elevated oxidative stress biomarkers. Journal of Nutrition. 146(4):758-766. doi: 10.3945/jn.115.222562.

Interpretive Summary: The consumption of omega-3 (n-3) fatty acids (FA,) mainly found in fatty fish, is thought to improve depressive symptoms. However, the evidence is limited especially among Puerto Ricans, a population burdened by depression. To fill this gap in knowledge, we examined the association between n-3 FA biomarkers and depressive symptoms as well as the potential impact of oxidative stress. We carried out this research in the Boston Puerto Rican Health Study with 787 participants aged approximately 57 years, the majority of whom were women. Urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) concentration, a measure of oxidative stress, and erythrocyte fatty acid composition, a measure of n-3 fatty acid consumption, were collected at baseline. We calculated an n-3 index as the sum of the most abundant n-3 fatty acids (eicosapentaenoic and docosahexaenoic acids) and expressed it as a percentage of total fatty acids. Baseline and 2-y depressive symptoms were collected. Our results show that among individuals with higher levels of oxidative stress, depressive symptoms were higher among those with a lower n-3 index. These data suggest that oxidative stress status may identify those who might benefit more from n-3 FA consumption to improve depressive symptoms.

Technical Abstract: Background: Omega-3 (n-3) fatty acid (FA) consumption is thought to improve depressive symptoms. However, current evidence is limited, and whether this association exists among Puerto Ricans, a population burdened by depression, remains uncertain. Objectives: We examined the association between omega-3 FA biomarkers and depressive symptoms as well as the potential influence of oxidative stress. Methods: Baseline and longitudinal analyses were conducted in the Boston Puerto Rican Health Study (n=787; participants aged 57+/-0.52 y, 73% women). Urinary 8-hydroxy-2’-deoxyguanosine (8-OHdG) concentration, a measure of oxidative stress, and erythrocyte FA composition were collected at baseline. We calculated the omega-3 index as the sum of eicosapentaenoic and docosahexaenoic acids, expressed as a percentage of total FAs. Baseline and 2-y depressive symptoms were characterized by using the Center for Epidemiological Studies-Depression Scale (CES-D). Statistical analyses included linear and logistic regression. Results: Urinary 8-OHdG concentration tended to modify the relation between the erythrocyte omega-3 index and baseline CES-D score (P-interaction = 0.10). In stratified analyses, the omega-3 index was inversely associated with CES-D score (beta = -1.74, SE = 0.88; P = 0.02) among those in the top quartile of 8-OHdG concentration but not among those in the lower quartiles. The relation between the omega-3 index and CES-D at 2-y was more clearly modified by 8- OHdG concentration (P-interaction = 0.04), where the omega-3 index was inversely associated with CES-D at 2-y, adjusted for baseline (beta = -1.66, SE = 0.66; P = 0.02), only among those with elevated 8-OHdG concentrations. Among individuals not taking antidepressant medications and in the top tertile of urinary 8-OHdG concentration, the omega-3 index was associated with significantly lower odds of a CES-D score >/= 16 at baseline (OR: 0.72; 95% CI: 0.53, 0.96) but not at 2-y (OR: 0.83; 95% CI: 0.60, 1.15). Conclusions: An inverse association between the omega-3 index and depressive symptoms was observed among participants with elevated oxidative stress biomarkers. These data suggest that oxidative stress may identify those who might benefit from omega-3 FA consumption to improve depressive symptoms.