Dose-dependent increases in heart rate variability and arterial compliance in overweight and obese adults with DHA-rich fish oil supplementation

Heart rate (HR) variability and large arterial compliance can be improved using fish oils. DHA, a component of fish oil, has cardiovascular health benefits, but its effect on HR variability (HRV) and arterial compliance is yet to be quantified. Sixty-seven overweight or obese adults (thirty-six males and thirty-one females; 53 (sem 2) year; BMI 31·7 (sem 1·1) kg/m²) were randomly allocated to consume either 6 g/d sunola oil (control; <i>n</i> 17), fish oil (260 mg DHA+60 mg EPA per g) at doses of 2 g/d (<i>n </i>16), 4 g/d (n 17) or 6 g/d (<i>n</i> 17). Blood pressure, HR and compliance of large and small arteries were measured while supine at baseline and after 12 weeks in all participants, and HRV was assessed in a subgroup of forty-six participants. There was no effect of fish oil on blood pressure, small artery compliance or HR. However, the low frequency:high frequency ratio of HRV decreased with increasing doses of fish oil (<i>r</i> − 0·34, <i>P</i> = 0·02), while large artery compliance increased (<i>r</i> 0·34, P = 0·006). Moreover, the changes in these biomarkers were significantly correlated (<i>r</i> − 0·31, P = 0·04) and may reflect fish oil-induced improvements in arterial function and cardiac autonomic regulation.