What Happens to Blood Pressure When You Take Fish Oil?

Fish oil from your diet or a supplement may help lower high blood pressure, which is a reading consistently higher than 130/80 milligrams of mercury (mm Hg). High blood pressure (hypertension) occurs when the pressure of your blood on the inside of your arteries is too high.

Fish Oil Lowers Blood Pressure

A growing body of scientific evidence shows that fish oil can lower blood pressure. Interest in fish oil’s effects on heart health increased in the 1970s, when scientists noticed that people in Japan, Greenland, and other nations and regions where diets included lots of fish had much lower rates of heart attack than in non-fish-eating areas.

A 2023 meta-analysis (an analysis of multiple studies) examined eight studies on omega-3 supplements and blood pressure among people with metabolic syndrome, a group of symptoms that increases the risk of various chronic diseases such as heart disease, stroke, and type 2 diabetes. Results included:

• Omega-3s reduced systolic and diastolic blood pressure, with systolic being the first number in a blood pressure reading, signifying the pressure against artery walls when the heart contracts, and diastolic being the second number in a reading, signifying the pressure on artery walls when the heart is at rest.
• They also observed improvements in participants’ cholesterol levels.

What Is Fish Oil?

Certain fatty, cold-water fish produce an oily substance in their tissues. This oil is high in omega-3s, a polyunsaturated fat known for various health benefits.

Fish oil contains two types of omega-3:

• Eicosapentaenoic acid (EPA)
• Docosahexaenoic acid (DHA)

You can get fish oil from supplements or by eating fish like salmon, tuna, or mackerel. Experts recommend that adults eat 8 ounces of seafood per week.

How Much Should You Take?

There are no official dietary guidelines for how much fish oil one should consume daily to reap health benefits.

However, in one meta-analysis of 71 studies, researchers looked at what dose of omega-3 supplements could lower blood pressure in individuals. They found that doses of 2 to 3 grams (g) per day for an average of 10 weeks significantly lowered blood pressure.

The researchers theorized that doses greater than 3 g may have additional benefits.

Adults with high blood pressure who took 3 g per day of omega-3 supplements reduced systolic blood pressure by 4.5 mm Hg. Those who did not have preexisting high blood pressure had a reduction in systolic blood pressure of 2 mm Hg.

The studies above looked into omega-3 fatty acids, rather than fish oil supplements. Most of the studies had participants take actual fish oil, but in some studies, participants took algal oil made from algae containing omega-3s. Some studies also looked at dietary fish intake, rather than fish oil supplements.

What Are Possible Side Effects and Considerations?

Fish oil supplements are known for having relatively few and mild side effects. The most common side effects are an unpleasant taste, “fishy” burps, or bad breath. Many supplements come in capsule form, and lemon extract or other flavors are added to counteract these effects.

Other possible fish oil side effects include:

• Diarrhea
• Headache
• Heartburn
• Nausea

Supplement quality is an important factor to consider when purchasing fish oil. In the United States, the Food and Drug Administration (FDA) does not regulate supplements, including fish oil, in the more stringent way it does for drugs.

Look for natural fish oil supplements with third-party testing in which an independent agency has verified the contents of a supplement, as well as a sustainability certificate from the Marine Stewardship Council.

What Other Lifestyle Changes Improve Blood Pressure?

Some lifestyle habits can help lower high blood pressure after a diagnosis or to maintain blood pressure that is healthy. Consider the following:

• Eat a well-balanced diet.
• Exercise regularly.
• Limit alcohol.
• Limit sodium.
• Manage stress.
• Quit smoking.

What Is the Importance of Treating High Blood Pressure?

High blood pressure should never go untreated. Uncontrolled high blood pressure can increase your risk of:

• Heart attack
• Heart disease
• Heart failure
• Kidney disease or failure
• Sexual dysfunction
• Stroke
• Vision loss

Always talk to a healthcare provider before trying any new supplements, and don’t try to treat high blood pressure on your own. Many people can manage their blood pressure with lifestyle changes, but some require medication to keep their blood pressure in a safe range.