Using Fish Oil to Reduce High Blood Pressure

Along with lifestyle changes like eating a healthy diet and losing extra weight, there's some evidence that adding fish oil to your diet may help keep blood pressure in check, as well as control high blood pressure (also known as hypertension).

Rich in omega-3 fatty acids (a form of polyunsaturated fat considered essential for good health), fish oil is typically sourced from cold-water fish such as salmon, mackerel, herring, sardines, and anchovies. Besides increasing your intake of omega-3-rich fish, you can find fish oil in dietary supplement form.

High blood pressure is closely associated with a dysfunction in the endothelium, the layer of cells lining your blood vessels. The endothelium is involved in a number of physiological processes affecting cardiovascular health, like the contraction and relaxation of blood vessels and blood clotting. Endothelial dysfunction is linked to plaque build-up in your arteries (atherosclerosis), a condition that can lead to heart attacks and stroke.

In preliminary research on animals, scientists have observed that fish oil may help improve endothelial function and improve the elasticity of your arteries.

The Research on Fish Oil for High Blood Pressure

Some research suggests that omega-3 fatty acids from fish oil supplements may aid in blood pressure control.

In a research review published in the American Journal of Hypertension in 2014, for instance, investigators sized up 70 previously published clinical trials examining the effects of the omega-3 fatty acids EPA and DHA from seafood, fortified foods, or supplements on people with or without high blood pressure.

The researchers found that the average systolic blood pressure (the top number in a blood pressure reading) decreased by 4.51 mm Hg in people who took DHA and EPA (compared to those taking a placebo). Diastolic blood pressure (the bottom number in a blood pressure reading) decreased by an average of 3.05 mm Hg.

In their analysis, the researchers found that among all people who took omega-3 fatty acids through supplements like fish oil, systolic blood pressure decreased by 1.75 mm Hg and diastolic blood pressure was lowered by 1.1 mm Hg (regardless of a person's blood pressure).

Side Effects of Fish Oil

Fish oil is likely safe for many people when taken in doses of three or fewer grams per day, according to the National Institutes of Health (NIH). The NIH cautions that taking more than 3 grams of fish oil daily (DHA and EPA combined) may inhibit blood clotting and increase the risk of bleeding.

Fish oil should be used cautiously (and only with supervision by a qualified healthcare professional) or avoided by people who bruise easily, have a bleeding disorder, or take certain medications or supplements that increase the risk of bleeding, such as warfarin, clopidogrel, aspirin, NSAIDs (such as ibuprofen), garlic, vitamin E, and the herb ginkgo biloba. It shouldn't be taken within two weeks of a scheduled surgery.

Use of fish oil may trigger a number of side effects, including bad breath, heartburn, and nausea. What's more, high doses of fish oil have shown both positive and negative influences on aspects of immune system function.

Keep in mind that supplements haven't been tested for safety and due to the fact that dietary supplements are largely unregulated, the content of some products may differ from what is specified on the product label. Two of the main concerns with fish oil are that the oil may be rancid or contain environmental contaminants found in fish such as PCBs (polychlorinated biphenyls) and mercury.

Also, the safety of supplements in pregnant women, nursing mothers, children, and those with medical conditions or who are taking medications has not been established. 

The Takeaway

Adopting healthy lifestyle practices such as exercising regularly, watching your salt intake, cutting back on alcohol consumption, avoiding smoking, and watching your weight may help you manage your blood pressure.

Adding omega-3 fatty acids from oily fish like salmon, anchovy, and sardines to your diet may also help. According to the NIH, a 3.5-ounce serving of these fish provides about 1 gram of omega-3 fatty acids. Keep in mind that some types of fish may contain high levels of mercury, PCBs, dioxins, and other environmental contaminants and that regular consumption of these fish may increase your body's levels of these contaminants.

In addition to possibly lowering blood pressure, fish oil may help enhance heart health by fighting heart disease, protecting against hardening of the arteries, and lowering cholesterol levels.

If you are considering taking fish oil supplements, be sure to speak with your healthcare provider first to see if it's appropriate and safe for you. Some medications and supplements commonly taken for high blood pressure (such as warfarin, aspirin, garlic, or gingko) may interact with fish oil.