Optimal omega-3 dose for lowering BP? Meta-analysis says 2–3 grams daily will suffice

Taking omega-3 polyunsaturated fatty acid (PUFA) at 2–3 grams daily is enough to yield a blood pressure (BP)-lowering effect, while higher doses may provide additional benefit to individuals at high risk of cardiovascular disease, according to a meta-analysis.

“We found evidence of a J‐shaped dose‐response curve, where the greatest reductions of systolic and diastolic BP occurred at moderate [combined] docosahexaenoic acid plus eicosapentaenoic acid (DHA+EPA) doses between 2 g/d and 3 g/d,” the investigators said.

At a DHA+EPA intake of 2 g/d, systolic and diastolic BP dropped by 2.61 (95 percent confidence interval [CI], −3.57 to −1.65) and 1.64 (95 percent CI, −2.29 to −0.99), respectively. The corresponding systolic and diastolic BP reductions at a DHA+EPA intake of 3 g/d were 2.61 (95 percent CI, −3.52 to −1.69) and 1.80 (95 percent CI, −2.38 to −1.23). [J Am Heart Assoc 2022;doi:10.1161/JAHA.121.025071]

Of note, there were prominent and approximately linear dose‐response associations observed, where increasing doses resulted in stronger reductions in systolic and diastolic BP across the subgroups of individuals with baseline systolic BP of ≥130 mm Hg, those with hyperlipidaemia, and those with an average age of ≥45 years.

Meanwhile, omega-3 PUFA intake above the recommended 3 g/d conferred no additional benefits in normotensive subgroups.

The meta-analysis included 71 trials that involved 4,973 individuals with a combined DHA+EPA dose of 2.8 g/d (interquartile range, 1.3–3.6 g/d). Most trials were restricted to participants without hypertension (n=56, average baseline SBP <140 mm Hg) and without hyperlipidaemia (n=57, average total cholesterol <200 mg/dL and triglycerides <150 mg/dL).

Average intervention duration was 10 weeks, with the duration >12 weeks (12–52 weeks) in 29 trials and <12 weeks in 42 trials. In most studies (n=64), supplementation was accomplished by capsuled fish oil, algal oil, or purified fish oil ethyl esters. A small number of studies used a dietary intervention that included fish meals (eg, mackerel, salmon, trout, and tuna) and other fish oil–fortified foods, either cooked at home or by a dietitian. Olive oil was the commonly used placebo.

“Our study builds on past evidence by examining the relationship using up‐to‐date literature and novel methods that allow for the estimation of a nonlinear trend that accounts for the correlation between studies,” said the investigators, adding that they are not the first to propose a nonlinear model for the dose‐response effect of fish oil on BP. [Nutrients 2016;8:58; Nutrients 2019;11:1232]

Taken together, the data show that intake of omega-3 PUFAs may have implications for a person’s future risk of stroke, ischaemic heart disease, and all‐cause mortality, they said. [BMJ 2020;368:m456]

The investigators acknowledged certain limitations to their study, saying that “[t]he intrinsically significant variations among original trials, such as the device of BP measurement (automatic vs manual), the year of study (conducted 1987–2020), and the type of intervention (diet vs supplementation) are likely to bring some uncertainty to our results and potentially weaken the conclusion.”