A meta-analysis of 71 randomized controlled trials has found the sweet spot for omega-3 fatty acid intake for lowering blood pressure: between 2 and 3 g/day. The investigators also reported that people at higher risk for cardiovascular disease may benefit from higher daily intake of omega-3.
The study analyzed data from randomized controlled trials involving 4,973 individuals and published from 1987 to 2020. Most of the trials used a combined supplementation of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Outcomes analysis involved the impact of combined DHA-EPA at 1, 2, 3, 4, or 5 grams daily on average changes in both systolic and diastolic BP and compared them with the placebo or control groups who had a combined intake of 0 g/day.
Dr. Xinzhi Li
“We found a significant nonlinear dose-response relationship for both SBP and DBP models,” wrote senior author Xinzhi Li, MD, PhD, and colleagues. Dr. Li is program director of the school of pharmacy at Macau University of Science and Technology in Taipa, China.
Most of the trials included in the meta-analysis evaluated fish oil supplements, but a number also included EPA and DHA omega-3 fatty acids consumed in food.
When the investigators analyzed studies that used an average baseline SBP of greater than 130 mm Hg, they found that increasing omega-3 supplementation resulted in strong reductions in SBP and DBP, but not so with people with baseline SBP below 130 mm Hg.
Across the entire cohort, average SBP and DBP changes averaged –2.61 (95% confidence interval, –3.57 to –1.65) and –1.64 (95% CI, –2.29 to –0.99) mm Hg for people taking 2 g/d omega-3 supplements, and –2.61 (95% CI, –3.52 to –1.69) and –1.80 (95% CI, –2.38 to –1.23) for those on 3 g/d. The changes weren’t as robust in higher and lower intake groups overall.
However, the higher the BP, the more robust the reductions. For those with SBP greater than 130 mm Hg, 3 g/d resulted in an average change of –3.22 mm Hg (95% CI, –5.21 to –1.23). In the greater than 80 mm Hg DBP group, 3 g/d of omega-3 resulted in an average –3.81 mm Hg reduction (95% CI, –4.48 to –1.87). In patients with BP greater than 140/90 and hypertension, the reductions were even more pronounced. And in patients with BP greater than 130/80, omega-3 intake of 4-5 g/d had a greater impact than 2-3 g/d, although that benefit didn’t carry over in the greater than 140/90 group.
High cholesterol was also a factor in determining the benefits of omega-3 supplementation on BP, as Dr. Li and colleagues wrote that they found “an approximately linear relationship” between hyperlipidemia and SBP, “suggesting that increasing supplementation was associated with greater reductions in SBP.” Likewise, the study found stronger effects on BP in studies with an average patient age greater than 45 years.
In 2019, the Food and Drug Administration issued an update that consuming combined EPA and DHA may lower BP in the general population and reduce the risk of hypertension, but that “the evidence is inconsistent and inconclusive.”
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“However, while our study may add a layer of credible evidence, it does not meet the threshold to make an authorized health claim for omega-3 fatty acids in compliance with FDA regulations,” Dr. Li said.
The study addresses shortcomings of previous studies of omega-3 and BP and by identifying the optimal dose, Marc George, MRCP, PhD, of the Institute of Cardiovascular Science, University College, London, and Ajay Gupta, MD, PhD, of the William Harvey Research Institute at Queen Mary University, London, wrote in an accompanying editorial. “More importantly, they have demonstrated a significantly stronger and increased BP-lowering effect in higher cardiovascular risk groups, such as those with hypertension or hyperlipidemia.”
They also noted that the 2.61–mm Hg reduction in SBP the study reported is “likely to be significant” on a population level. “A 2–mm Hg reduction in SBP is estimated to reduce stroke mortality by 10% and deaths from ischemic heart disease by 7%,” they wrote. “Expressed another way, an analysis in the U.S. population using 2010 data estimates that a population-wide reduction in SBP of 2 mm Hg in those aged 45- 64 years would translate to 30,045 fewer cardiovascular events ([coronary heart disease], stroke, and heart failure).”
The investigators and editorialists have no disclosures.