Abstract
BACKGROUND/OBJECTIVES: The Omega-3 Index (O3I), which is the total eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in erythrocytes as a percentage of total fatty acids (FAs), is associated with fish intake. O3I also varies with body mass index, age, sex, and dietary factors other than the intake of n-3 polyunsaturated fatty acids (PUFAs). This study examined the relationship between the dietary intake of total fat and FA classes, and O3I, specifically regarding EPA+DHA intake. SUBJECTS/METHODS: Data on dietary intake and serum FAs from 2,370 participants (1,192 males and 1,178 females) aged 18-79 yrs, collected during the 2011-2012 National Health and Nutrition Examination Survey, were used in this study. The O3I was estimated from the serum EPA+DHA content. RESULTS: In the total population, O3I showed an inverse correlation with the intake of total fat (r = -0.417), saturated FAs (SFAs; r = -0.423), and monounsaturated fatty acids (MUFAs; r = -0.412) (P < 0.01). Similar relationships were observed among males. However, in females, only SFA intake was correlated with O3I (r = -0.386, P < 0.05). In contrast, no correlation was observed between n-6 PUFA intake and O3I. Multivariable regression analysis also showed that a 1% increment in energy provided by total fat, SFA, and MUFA corresponded to reductions of 0.019, 0.055, and 0.035 units in O3I, respectively (P < 0.01). Both SFA and MUFA intakes mediated the negative relationship between total fat intake and O3I in the total population and males. However, MUFA were not significant mediators in women. CONCLUSION: The intakes of total fat, SFA, and MUFA negatively influenced O3I, independent of n-3 PUFA intake.