Fish oil, which contains omega-3 fatty acids, is found in foods like fatty fish and has been linked to heart health benefits, especially lowering triglycerides. But evidence is mixed on whether fish oil supplements meaningfully reduce blood pressure.
Overall, research on fish oil and blood pressure is inconsistent. “Some studies have shown that fish oil may help to lower blood pressure and others have not,” said Lauren Hynicka, PharmD, BCPS, an associate professor of practice, sciences, and health outcomes research at the University of Maryland School of Pharmacy.
A 2022 analysis found that people who consumed 2 to 3 grams of omega-3 fatty acids per day experienced a modest average reduction in blood pressure, with the most noticeable effects seen in those who had elevated blood pressure to begin with. Still, it’s unclear whether fish oil would provide any additional benefits for people who are already taking prescription medications to manage blood pressure. “Those with normal blood pressure usually experience little to no change in their own blood pressure when taking fish oil,” said Michelle Routhenstein, MS, RD, CDCES, CDN, a cardiology dietitian at Entirely Nourished.
One reason findings have been inconsistent is the wide variation among fish oil products on the market, which contain differing ratios of the two main types of omega-3s, DHA and EPA. Studies also test a range of dosages, some of which appear to have an effect, while others do not. “It is possible that the dose of fish oil makes a difference in the effect seen on blood pressure,” Hynicka said. “But the research is mixed.”
While there isn’t conclusive evidence that taking fish oil can lower blood pressure, studies linking fish oil to reduced blood pressure suggest the supplement may help blood vessels relax and widen. In theory, this could decrease inflammation and improve overall blood vessel function, Hynicka said.
Researchers also believe omega-3s reduce oxidative stress, an accumulation of free radicals that can damage cells and is thought to contribute to elevated blood pressure.
While fish oil is generally well tolerated, it isn’t without potential side effects. These range from mild issues, such as a fishy aftertaste and heartburn, to more serious problems, including a possible increased risk of atrial fibrillation and stroke. Elevated LDL cholesterol and bleeding complications have also been reported, added Amin Yehya, MD, a cardiologist at Sentara Heart Hospital in Norfolk, Virginia.
It’s also important to know that, unlike prescription medications, supplements are not regulated by the Food and Drug Administration (FDA), meaning they aren’t approved and evaluated for safety and effectiveness before hitting the market. To help ensure quality, experts recommend choosing products that have been tested by a third-party lab for purity and accurate labeling.
Because of the relatively high doses required, the potential for side effects, and the availability of more effective blood pressure treatments, clinicians do not routinely recommend fish oil supplements, Yehya said. Instead, experts encourage getting omega-3s from food. Fatty fish such as salmon, mackerel, albacore tuna, trout, and sardines are all good sources, and the American Heart Association suggests two 3.5 ounce servings a week.
For people who don’t eat fish, supplements may fill a gap, said Routhenstein. Still, “nutrition and lifestyle changes are far more effective” for supporting healthy blood pressure, he said. Those include prioritizing sleep, regularly exercising, avoiding risky substances like alcohol, limiting sodium, and managing stress.
As with any supplement, it’s best to talk to your doctor or a pharmacist before starting fish oil. They “will be able to provide you with information about the risks and benefits of the dietary supplement based on your other health information and help you decide if the supplement is right for you,” Hynicka said.
