The Omega-3 Index Response to an 8 Week Randomized Intervention Containing Three Fatty Fish Meals Per Week Is Influenced by Adiposity in Overweight to Obese Women

Abstract

Background: The Dietary Guidelines for Americans (DGA) recommends consuming ~225 g/wk of a variety of seafood providing >1.75 g/wk of long-chain omega-3 fatty acids to reduce cardiovascular disease risk, however individual responses to treatment vary.

Objective: This study had three main objectives. First, to determine if a DGA-conforming diet (DGAD), in comparison to a typical American diet (TAD), can increase the omega-3 index (OM3I), i.e., the red blood cell mol% of eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA). Second, to identify factors explaining variability in the OM3I response to dietary treatment. Third to identify factors associated with the baseline OM3I.

Design: This is a secondary analysis of a randomized, double-blind 8 wk dietary intervention of overweight/obese women fed an 8d rotating TAD (n = 20) or DGAD (n = 22) registered at www.clinicaltrials.gov as NCT02298725. The DGAD-group consumed 240 g/wk of Atlantic farmed salmon and albacore tuna in three meals with an estimated EPA + DHA of 3.7 ± 0.6 g/wk. The TAD-group consumed ~160 g/wk of farmed white shrimp and a seafood salad containing imitation crab in three meal with an estimated EPA + DHA of 0.45 ± 0.05 g/wk. Habitual diet was determined at baseline, and body composition was determined at 0 and 8wks. Red blood cell fatty acids were measured at 0, 2 and 8 wk.

Results: At 8 wk, the TAD-group OM3I was unchanged (5.90 ± 1.35-5.80 ± 0.76%), while the DGAD-group OM3I increased (5.63 ± 1.27-7.33 ± 1.36%; p < 0.001). In the DGAD-group 9 of 22 participants achieved an OM3I >8%. Together, body composition and the baseline OM3I explained 83% of the response to treatment variability. Baseline OM3I (5.8 ± 1.3%; n = 42) was negatively correlated to the android fat mass (p = 0.0007) and positively correlated to the FFQ estimated habitual (EPA+DHA) when expressed as a ratio to total dietary fat (p = 0.006).

Conclusions: An 8 wk TAD did not change the OM3I of ~6%, while a DGAD with 240 g/wk of salmon and albacore tuna increased the OM3I. Body fat distribution and basal omega-3 status are primary factors influencing the OM3I response to dietary intake in overweight/obese women.

Keywords: Dietary Guidelines for Americans; dietary intervention; fish; omega-3 fatty acids; omega-3 index; omega-3 response; overweight women; typical American diet.

Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Copyright © 2022 Richardson, Krishnan, Gray, Keim and Newman.

Figures

Figure 1

Study flow diagram documenting participant enrollment, allocation, follow-up and analysis. This diagram conforms the Consolidated Standards of Reporting Trials (i.e., CONSORT). TAD, typical American diet; DGAD, Dietary Guidelines for American's diet; FAMEs, red blood cell fatty acid analysis; QC, quality control criterion.

Figure 2

Omega-3 index response rate variance by diet group and time. Participants within the typical American diet (TAD; n = 20) and Dietary Guidelines for Americans diet (DGAD; n = 22) groups were clustered based on the 0–8 wk rate of OM3I change and the average OM3I(Wk0) and OM3I(Wk2), by K-means clustering, with each diet group being segregated into three groups of participants with different responses. As a significant change between Wk0 and Wk2 was not detected (Table 3), this term was applied to provide a better estimate of the baseline OM3I for this analysis and particularly stabilized the TAD-group clustering. Participant measures and regression lines share common colors.

Figure 3

Variance in omega-3 index response to typical American diet (TAD) and Dietary Guidelines for American's diet (DGAD) interventions. (A) The 8 wk OM3I change (OM3I(Wk8−Wk0)) expressed as a function of baseline omega 3 index (OM3I(Wk0)). Diet (p < 0.0001), OM3I(Wk0) (p = 0.0003), and diet x OM3I(Wk0) interactions (p = 0.036) were detected. (B) Participants within diet groups were clustered according to their OM3I(Wk8−0):OM3I(Wk0) ratio by hierarchical cluster analysis and projected onto both 2 wk (top) and 8 wk (bottom) data. Hierarchical cluster analysis identified low (blue) and high (orange) responding subgroups in the DGAD group. The correlations between OM3I(Wk0) and magnitude of change were significant in the DGAD high, but not low response subgroups.

Figure 4

Body composition and the baseline omega-3 index (OM3I(Wk0)) explain the dose-dependent 8 wk change in the OM3I (Log[ΔOM3I(Wk8−0)/(EPA+DHA)]). (A) Actual x Predicted plot from the stepwise linear regression of the Log[ΔOM3I(Wk8−0)/(EPA+DHA)] using body composition factors and OM3I(Wk0) explaining 83% of the variance. (B) Regression equation and model components. (C–H) Leverage plots with p-values and the standardized beta coefficient (bs) for each model component: (C) lean body mass; (D) trunk %fat; (E) OM3I(Wk0); (F) android fat; (G) BMI; (H) OM3I(Wk0) × android fat interactions. Symbols: orange circles—high responding subgroup of the Dietary Guidelines for American Diet group defined in Figure 3B; blue circles—low responding subgroup of the Dietary Guidelines for American Diet group defined in Figure 3B. bs, standardized beta-coefficient; RMSE, root mean square error.

Figure 5

Pearson's correlation heatmap of the baseline omega-3 index, habitual omega-3 fatty acid factors and DXA-dependent body composition measures. Correlation statistics are calculated on normally transformed data, with positive (orange) and negative (blue) correlation strength indicated by color intensity. Variables were clustered in JMP v16 using implementation of the SAS VARCLUS algorithm. Clusters are ranked by decreasing order of explained variance. Variables are ordered within clusters by their correlation strength with the baseline omega-3 index (OM3I(Wk0)). FFQ, food frequency questionnaire; SFAT, dietary saturated fat; TFAT, dietary total fat.