Effects of omega-3 fatty acid supplementation on heart rate variability

Table 1 Risk of bias assessment

Ref.	Domain 1: Randomization process	Domain 2: Deviations from intended interventions	Domain 3: Missing outcome data	Domain 4: Measurement of the outcome	Domain 5: Selection of reported results	Overall risk of bias (auto)
Ninio et al[8], 2008	Low risk	Low risk	Low risk	Low risk	Low risk	Low risk
Sjoberg et al[9], 2009	Low risk	Low risk	Low risk	Low risk	Low risk	Low risk
Baumann et al[10], 2018	High risk	Some concerns	Low risk	Some concerns	Low risk	High risk
Ibrahim et al[11], 2025	Low risk	Low risk	Low risk	Low risk	Low risk	Low risk

Table 2 Summary of included studies

Ref.	Country	Study design	Population/sample size	Intervention/exposure	Comparator	Outcome(s)	Duration	Main findings	Type and dose of omega-3 fatty acid, mg/day
Ninio et al[8], 2008	Australia	A randomized, double-blind, parallel trial	Fifty overweight, sedentary adults with risk factors for coronary disease	DHA-rich fish oil 6 g/day (providing 1.56 g DHA + 0.36 g EPA) (n = 23)	Sunflower seed oil (placebo) (n = 27)	Resting heart rate, heart rate during submaximal exercise, and HRV parameters (high-frequency and low-frequency power)	12 weeks	DHA-rich fish oil significantly increased high-frequency power (indicative of enhanced parasympathetic/vagal tone). Resting heart rate and heart rate during exercise were significantly reduced compared with placebo	DHA-rich fish oil: Approximately 1560 mg DHA/day and approximately 360 mg EPA/day (total 6 g fish oil)
Sjoberg et al[9], 2009	Australia	A randomized, double-blind, placebo-controlled, parallel dose-response supplementation trial	Thirty-four overweight or obese adults	DHA-rich fish oil (n = 17)	Placebo (6 g/day of sunola oil) (n = 17)	HRV, specifically the low frequency, high frequency, and (LF/HF) ratio	12 weeks	The LF/HF ratio of HRV decreased with increasing doses of fish oil. The changes in these biomarkers may reflect that fish oil-induced improvements in arterial function and cardiac autonomic regulation	The 2, 4, and 6 g/day doses of fish oil provided 0.52, 1.04, and 1.56 g DHA/day, respectively
Baumann et al[10], 2018	Germany	A parallel randomized interventional control trial	20 obese children/adolescents (BMI > 95th percentile)	Daily omega-3 fatty acid supplementation (fish oil capsules)	Same obese subjects before supplementation	Time-domain HRV parameters (SDNN, RMSSD, pNN50)	At least 3 months, average of approximately 214 days (≈ 7 months) between baseline and follow-up ECG in the obese group	Omega-3 fatty acid supplementation may be used for cardiovascular prophylaxis in obese children and adolescents	Fish oil capsules containing at least 400 mg EPA and 120 mg DHA per day
Ibrahim et al[11], 2025	Egypt	A parallel randomized interventional control trial	30 overweight and obese children	Omega-3 supplementation	Same obese children before supplementation	HRV differences in RMSSD, SDNN, pNN50%, and lipid profiles	3 months	Significant increases in HRV measures (RMSSD, SDNN, pNN50) in the omega-3 group compared to controls. Significant improvements in lipid profile: Decreased triglycerides and increased HDL in the omega-3 group	400 mg EPA and 200 mg DHA daily for 3 months was taken (the ratio of EPA to DHA to 2:1)

BMI: Body mass index; DHA: Docosahexaenoic acid; EPA: Eicosapentaenoic acid; HDL: High-density lipoprotein; HRV: Heart rate variability; LF/HF ratio: Low-to-high-frequency ratio; pNN50%: Percentage of successive normal-to-normal intervals differing by more than 50 milliseconds; RMSSD: Root mean square of successive differences; SDNN: Standard deviation of normal-to-normal intervals.