A comparison of heart rate variability, n-3 PUFA status and lipid mediator profile in age- and BMI-matched middle-aged vegans and omnivores

Low heart rate variability (HRV) predicts sudden cardiac death. Long-chain (LC) n-3 PUFA (C20-C22) status is positively associated with HRV. This cross-sectional study investigated whether vegans aged 40-70 years (n 23), whose diets are naturally free from EPA (20 : 5n-3) and DHA (22 : 6n-3), have lower HRV compared with omnivores (n 24). Proportions of LC n-3 PUFA in erythrocyte membranes, plasma fatty acids and concentrations of plasma LC n-3 PUFA-derived lipid mediators were significantly lower in vegans. Day-time interbeat intervals (IBI), adjusted for physical activity, age, BMI and sex, were significantly shorter in vegans compared with omnivores (mean difference -67 ms; 95% CI -130, -3.4, P < 0.05), but there were no significant differences over 24 h or during sleep. Vegans had higher overall HRV, measured as 24 h standard deviation of normal-to-normal intervals (SDNN) (mean adjusted difference 27 ms; 95% CI 1, 52, P = 0.039). Conversely, vegans presented with decreased 8 h day-time HRV: mean adjusted difference in SDNN -20 ms; 95% CI -37, -3, P = 0.021, with no differences during nocturnal sleep. Day-time parameters of beat-to-beat HRV (root of the mean of the sum of the squares of differences between adjacent normal-to-normal intervals, percentage of adjacent normal-to-normal intervals that differ by > 50% and high-frequency power) were similarly lower in vegans, with no differences during sleep. In conclusion, vegans have higher 24 h SDNN, but lower day-time HRV and shorter daytime IBI relative to comparable omnivores. Vegans may have reduced availability of precursor markers for pro-resolving lipid mediators; it remains to be determined whether there is a direct link with impaired cardiac function in populations with low-n-3 status.