Effects of Fish Oil on Blood Pressure

Medically reviewed by Lindsay Cook, PharmD

• Fish oil is a rich source of omega-3 fatty acids, promoting heart health.

• However, studies on the impact of fish oil supplements on blood pressure yield mixed results.

• Some research indicates that individuals with high blood pressure may benefit the most from fish oil consumption.

Fish oil, packed with omega-3 fatty acids, is typically found in fatty fish and is linked to numerous heart health advantages, particularly in lowering triglyceride levels. Nonetheless, the evidence regarding fish oil supplements and their effect on blood pressure remains inconsistent.

How Fish Oil Impacts Blood Pressure

Research exploring the relationship between fish oil and blood pressure presents varying outcomes. “Some studies have found fish oil effective in lowering blood pressure, while others have not,” explains Lauren Hynicka, PharmD, BCPS, an associate professor at the University of Maryland School of Pharmacy.

A 2022 analysis revealed that individuals consuming 2 to 3 grams of omega-3 fatty acids daily experienced a modest reduction in blood pressure, particularly noteworthy among those with elevated blood pressure. However, it is uncertain whether additional benefits would accrue to those already on prescription medications for hypertension. “Individuals with normal blood pressure generally do not see significant changes when taking fish oil,” mentions Michelle Routhenstein, MS, RD, CDCES, CDN, a cardiology dietitian.

The inconsistency in findings stems partly from the diverse range of fish oil products on the market, which contain varying proportions of the key omega-3 types, DHA and EPA. Studies also utilize different dosages; some appearing to have an impact, while others do not. “The amount of fish oil ingested may influence its effect on blood pressure,” Hynicka notes. “But the research is far from conclusive.”

Why Fish Oil May Positively Influence Blood Pressure

Although conclusive proof of fish oil’s ability to lower blood pressure is lacking, some studies suggest it may help relax and widen blood vessels. This effect could theoretically reduce inflammation and enhance overall blood vessel function, according to Hynicka.

Researchers also propose that omega-3s help mitigate oxidative stress, a build-up of free radicals that can damage cells and is linked to higher blood pressure.

Risks and Considerations

Generally, fish oil is well tolerated, yet it can have side effects ranging from mild issues, such as a fishy aftertaste and heartburn, to more severe complications, including a possible increased risk of atrial fibrillation and stroke. There have also been reports of elevated LDL cholesterol and bleeding problems, noted Amin Yehya, MD, a cardiologist.

Unlike prescription medications, dietary supplements are not regulated by the Food and Drug Administration (FDA), meaning they are not vetted for safety and efficacy prior to market release. To ensure quality, experts recommend selecting products tested by a third-party laboratory for purity and accurate labeling.

Given the relatively high doses needed and potential side effects, along with the existence of more effective blood pressure treatments, healthcare professionals do not typically recommend fish oil supplements. Instead, they advise obtaining omega-3s from dietary sources. Fatty fish such as salmon, mackerel, albacore tuna, trout, and sardines are excellent sources, with the American Heart Association recommending two servings of 3.5 ounces weekly. For those who do not consume fish, supplements might be an alternative, according to Routhenstein. However, he emphasizes that “nutrition and lifestyle changes are far more effective” in promoting healthy blood pressure. These changes may include prioritizing sufficient sleep, engaging in regular physical activity, avoiding harmful substances like alcohol, limiting sodium intake, and managing stress levels.

As with any supplement, consulting your doctor or pharmacist before starting fish oil is advisable. They can provide insights into the risks and benefits of this dietary supplement based on your individual health profile and help determine if it is suitable for you, Hynicka concludes.

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