Omega-3 Fatty Acids and Blood Pressure

Whether omega-3 fatty acids directly lower blood pressure is still debated. However, positive effects of omega-3s have been shown in people with early heart disease. In a Red Hand safety notice, the Federal Institute for Drugs and Medical Devices (BfArM) warned in November 2023 that, depending on the dose of the omega-3 products taken, certain people experienced increased rates of atrial fibrillation.

What are omega-3 fatty acids?

Omega-3 fatty acids are polyunsaturated fatty acids.

Unsaturated fatty acids are important for the immune system, blood clotting and the formation of nerve cells. They are components of cell membranes and building blocks for signaling molecules, hormones and inflammation mediators. They are essential, meaning the body cannot make them and they must be taken in through the diet.

How omega-3 works

The most important and best-studied omega-3s are EPA and DHA (found in fatty cold-water fish such as carp, eel, salmon, mackerel, etc.; plant-based source: microalgae oil) and alpha-linolenic acid (found only in plants, for example in rapeseed, hemp, walnut or flaxseed oil).

The effect of DHA was examined by two research teams. They found that DHA can bind at specific sites on muscle cells and open potassium channels there, allowing potassium to flow out of the cell. As a result, the muscle cell relaxes. The idea that this causes blood vessels to widen and blood pressure to drop was confirmed in experiments on anesthetized mice.

A study published on 01.06.2022 was also able to show a blood-pressure-lowering effect of omega-3 fatty acids in people. The effect was larger the higher the starting blood pressure. The biggest reduction was seen with a daily dose of 3 g of omega-3 fatty acids. According to the study, these can be taken as dietary supplements or obtained from food.

In summer 2023, however, the Swiss Medical Forum and Medical Tribune questioned the results of many studies because most studies on omega-3 supplements were not blinded. In addition, the placebo used in some control groups may have had an unfavorable effect on the expected outcome. It is therefore possible that the positive effects found are due less to the benefit of the omega-3 product in the treatment group and more to an adverse effect of the placebo in the control group.
They also point out that fish contain only small amounts of omega-3s. To produce enough fish oil capsules to meet demand, a very large amount of fish must be caught and processed, which contributes to overfishing and disrupts the marine ecosystem. Traces of PCBs and dioxins can also be detected in finished fish oil capsules. These do not have effects at low intake but can be harmful at high doses. So be sure to choose high-quality fish oil capsules.

Positive effects of omega-3

Omega-3 fatty acids are also credited with the following positive effects:

Protection against heart rhythm disturbances
Stabilization of atherosclerotic plaques, reducing the risk that plaques will rupture and cause a heart attack or stroke
Prevention or slowing of the progression of coronary heart disease (CHD)
Inhibition of platelet aggregation improving blood flow and promoting circulation
Positive effects on certain inflammation mediators
Lowering of triglyceride levels
Evidence that the risk of dementia or depression may be reduced

Side effects of omega-3

Side effects are also known.

Side effects of omega-3 medications

There are also medications that contain omega-3 ethyl esters for example, icosapent ethyl is named as an ingredient which may be prescribed to people with high blood lipid levels. These are prescription drugs. The side effects are described in more detail. In addition to nausea, abdominal pain, inflammation of the mucous membrane in the gastrointestinal tract and taste disturbances, dizziness is also listed. For one medication that was, however, temporarily unavailable in Germany due to a pricing dispute, bleeding, edema, atrial fibrillation, constipation, muscle and bone pain, gout and skin rashes were known as unwanted but possible side effects. The Federal Institute for Drugs and Medical Devices (BfArM) warned in a so-called Red Hand letter in November 2023 that atrial fibrillation occurred more often in people with cardiovascular disease or cardiovascular risk factors. This was dependent on the dose of omega-3 fatty acids the study participants received. The risk of developing atrial fibrillation was highest with a daily dose of 4 g.

Side effects of omega-3 supplements

For omega-3 products sold as dietary supplements, fishy burps and bad breath are common; less often people report feeling unwell or having stomach or intestinal problems.

As noted above, increased atrial fibrillation was seen with omega-3 medications. In the related statement the Federal Institute for Risk Assessment (BfR) explicitly addresses dietary supplements:

Omega-3 dietary supplements are often sold as fish oil capsules and sometimes contain doses similar to medicines. Unlike medicines, dietary supplements are freely available on the market and can be taken for long periods without medical supervision. Potentially harmful health effects can therefore be overlooked more easily.

The Federal Institute for Risk Assessment (BfR) therefore recommends that consumers with heart disease or corresponding risk factors take omega-3-containing products, such as dietary supplements, only after consulting a doctor, especially if taken over a longer period.

The Omega-3 Index

The so-called Omega-3 Index refers to the share of omega-3 fatty acids among total fatty acids in the membranes of red blood cells. If this is below 4 percent, the risk of sudden cardiac death is ten times higher compared with an index above 8 percent.

For comparison: in Germany the average Omega-3 Index is around 4 percent which corresponds to 148 cases of sudden cardiac death per 100,000 people. In Japan the average Omega-3 Index is around 11 percent sudden cardiac death affects only 7.8 out of 100,000 people there.

The ratio of omega-3 to omega-6 fatty acids

It is not only the amount of omega-3 fatty acids you consume that matters. In our diet we generally take in relatively large amounts of omega-6 fatty acids, which act as counterparts to omega-3s. The breakdown of linoleic acid (an omega-6 fatty acid) to arachidonic acid uses the same enzyme system as the conversion of alpha-linolenic acid (an omega-3) to EPA. If as is common in Western diets there is an excess of linoleic acid, less alpha-linolenic acid can be converted.

Therefore it is important to maintain a balanced ratio of omega-6 to omega-3 fatty acids. The German Nutrition Society (DGE) recommends a ratio of no more than 5:1. That means taking at most five times as many omega-6 as omega-3 fatty acids. Currently the ratio is usually about 8:1.

To get enough of the beneficial omega-3 fatty acids, the German Nutrition Society recommends two fish meals per week or an intake of EPA and DHA of 250 mg/day. However, the effectiveness of taking them in capsule form is repeatedly questioned.

If you change your diet accordingly, eat fish and prefer valuable plant oils (for example flaxseed, microalgae, chia, camelina or hemp oil for cold use, and rapeseed oil for both cooking and cold use) over unhealthy saturated animal fats, you will benefit in several ways. On the one hand you will likely get the more useful form of omega-3 fatty acids this way, and on the other hand a fish meal will often replace a less healthy red-meat meal.

Fish	Omega-3 fatty acid content
Atlantic salmon, farmed, cooked, smoked	1.8%
Anchovies – Europe, preserved in oil or salt	1.7%
Sardine – Pacific Ocean, packed in tomato sauce or salt, with bones	1.4%
Atlantic herring, pickled in vinegar	1.2%
Mackerel – Atlantic, cooked, smoked	1%
White tuna – packed in water or salt	0.7%

As a plant-based alternative to fish, flaxseed oil is the most important source because it contains alpha-linolenic acid in the most concentrated form. The body can convert this (to a limited extent) into the longer-chain omega-3 fatty acids. Naturally, whole flaxseed is also high in ALA and, when ground and taken with enough liquid, is easy to absorb. Hemp oil and walnuts or walnut oil are also good plant sources of alpha-linolenic acid. Other, currently more exotic sources include chia, perilla, sacha inchi and camelina oil. The latter should not be confused with flaxseed oil it comes from a different plant.

Plant oils	Omega-3 fatty acid content
Flaxseed oil	56-71%
Chia oil	up to about 64%
Perilla oil	about 60%
Sacha Inchi oil	about 48%
Camelina oil	about 38%
Hemp oil	about 17%
Walnut oil	about 13%
Rapeseed oil (canola)	about 9%
Soybean oil	about 8%

Omega-6 fatty acids

When reading about the benefits of omega-3 fatty acids, you will often also read about omega-6s and the need to keep the two in balance. The recommendation is 5:1. That means you should take in at most five times as many omega-6 fatty acids as omega-3s. That's hard to do if you don't know what they are and which foods contain them.

Omega-6 fatty acids are also polyunsaturated. Some of them are essential and must be obtained through the diet because the body cannot make them.

The most important omega-6 fatty acids are linoleic acid, gamma-linolenic acid and arachidonic acid. Linoleic acid is the essential omega-6 that must be supplied in the diet. The other two and further fatty acids can be made from it in the body.

Functions of omega-6 fatty acids

Omega-6s are components of cell membranes. They also serve as precursors for various substances. They are involved in growth and repair processes and lower the bad LDL cholesterol, but unfortunately also lower the good HDL cholesterol.

The arachidonic and gamma-linolenic acids formed from linoleic acid have more specific roles. Arachidonic acid is not only part of the cell membrane it also serves as a basis for making tissue hormones (eicosanoids). These produce free radicals that are needed to defend against harmful substances. But in doing so they also promote inflammatory processes in the body and act to constrict blood vessels. Gamma-linolenic acid, on the other hand, has anti-inflammatory effects.

Sources of omega-6 fatty acids

Omega-6 fatty acids are found in many foods. So you generally don't need to worry about getting enough.

Linoleic acid is found in large amounts, for example, in safflower and sunflower oil. It is also present in meat and meat products from conventional farming because farm animals are often fed linoleic-acid-rich feed.

Arachidonic acid is found especially in animal fats, muscle meat and offal, eggs (especially in the yolk) and milk fat.

Gamma-linolenic acid is found in pomegranate seeds and hemp oil.

Omega-6 fatty acids are therefore important for the body too. However, too much can be harmful.

Sources

This article comes from BloodPressureDB – the leading app since 2011 that helps hundreds of thousands monitor their blood pressure every day. Our content is based on carefully researched, evidence-based data and is continuously updated (as of 01/2026).

Author Sabine Croci is a qualified medical assistant with many years of experience in internal medicine and cardiology practices as well as in outpatient care, and has led BloodPressureDB's specialist editorial team since 2015. Thanks to her extensive additional qualifications as a paramedic, first responder and in various therapy and emergency areas, she provides solid, practical and reliably reviewed information.