DHA-Rich Fish Oil Increases the Omega-3 Index in Healthy Adults and Slows Resting Heart Rate without Altering Cardiac Autonomic Reflex Modulation

Regular fish consumption, a rich source of long-chain omega-3 (ω-3) docosahexaenoic acid (DHA), modifies cardiac electrophysiology. However, human studies investigating fish oil and cardiac electrophysiology have predominantly supplemented therapeutic (high) doses of fish oil (often ω-3 eicosapentaenoic acid (EPA) rich sources). This study examined whether non-therapeutic doses of DHA-rich fish oil modulate cardiac electrophysiology at rest and during cardiovascular reflex challenges to the same extent, if at all, in young healthy adults.

Participants (N = 20) were supplemented (double-blinded) with (2x1g.day^-1) soy oil (Control n = 9) or DHA-rich tuna fish oil (FO n = 11) providing DHA: 560 mg and EPA: 140 mg. The Omega-3 Index (O3I; erythrocyte membrane % EPA + DHA), heart rate (HR) and HR variability (HRV) were analyzed during rest, maximal isometric handgrip and cold diving reflex challenges at baseline and following 8 weeks.

The baseline O3I (Control: 5.1 ± 1.0; FO: 5.4 ± 0.9; P > 0.05), resting HR (Control: 65 ± 12bpm; FO: 66 ± 8bpm; P > 0.05) and HRV metrics did not significantly differ between the groups prior to supplementation. Relative to the control group, the O3I was increased (Control: 5.0 ± 1.1; FO: 7.8 ± 1.2; P < 0.001), and resting HR was slowed in the FO group following supplementation (Control: 66 ± 9bpm; FO: 61 ± 6bpm; P = 0.046). However, no significant (P > 0.05) between-group differences were observed in HR responsiveness or any indices of HRV during reflex challenges.

In young healthy adults, dietary achievable doses of ω-3 DHA-rich fish oil exerted a direct slowing effect on resting HR, without compromising the HR response to either dominant sympathetic or parasympathetic modulation.

Cardiovascular recovery from psychological and physiological challenge and risk for adverse cardiovascular outcomes and all-cause mortality

OBJECTIVE

Exaggerated cardiovascular (CV) reactivity to laboratory challenge has been shown to predict future CV morbidity and mortality. CV recovery has been less studied and has yielded inconsistent findings, possibly due to the presence of moderators. Reviews on the relationship between CV recovery and CV outcomes have been limited to cross-sectional studies and have not considered methodological factors. We performed a comprehensive meta-analytic review of the prospective literature investigating CV recovery to physical and psychological challenge and adverse CV outcomes.

METHODS

We searched PsycINFO and PubMed for prospective studies investigating the relationship between CV recovery and adverse CV outcomes. Studies were coded for variables of interest and for effect sizes. We conducted a random-effects weighted meta-analysis. Moderators were examined with analysis of variance-analog and meta-regression analyses.

RESULTS

Thirty-seven studies met the inclusion criteria (n = 125,386). Impaired recovery from a challenge predicted adverse CV outcomes (summary effect, r = 0.17, p < .001). Physical challenge was associated with larger predictive effects than psychological challenge. Moderator analyses revealed that recovery measured at 1 minute postexercise, passive recovery, use of mortality as an outcome measure, and older sample age were associated with larger effects.

CONCLUSIONS

Poor recovery from laboratory challenges predicts adverse CV outcomes, with recovery from exercise serving as a particularly strong predictor of CV outcomes. The overall effect size for recovery and CV outcomes is similar to that observed for CV reactivity and suggests that the study of recovery may have incremental value for understanding adverse CV outcomes.