Omega-3 fatty acids and blood pressure

Whether omega-3 fatty acids can directly lower blood pressure is controversial. However, positive effects of omega-3 fatty acids have been shown in people with early heart disease. In a so-called "Red Hand" letter 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 atrial fibrillation.

What are omega-3 fatty acids?

Omega-3 fatty acids are polyunsaturated fats.

Unsaturated fatty acids are important for the immune system, blood clotting and the development of nerve cells. They are part of cell membranes and are the starting material for signaling molecules, hormones and inflammation mediators. They are essential, meaning the body cannot make them and they must be obtained from the diet.

Effects of omega-3

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

The effect of DHA was investigated by two research teams. They discovered that DHA can bind at certain 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 hypothesis that this leads to vessel dilation and a drop in blood pressure was demonstrated in experiments with anesthetized mice.

A study published on 01.06.2022 was able to show a blood-pressure-lowering effect of omega-3 fatty acids in humans. The effect was greater the higher the starting blood pressure. The largest 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 through food.

In summer 2023 the Swiss Medical Forum and the Medical Tribune questioned the results of many studies because most studies on omega-3 supplements were not blinded. In some cases the control group received a placebo that might have had an unfavorable effect on the expected result. It is therefore possible that the reported positive effects for the omega-3 products under study are due less to a beneficial effect in the treatment group and more to an unfavorable effect of the placebo in the control group.
They also point out that fish contain only small amounts of omega-3 fatty acids. To meet the demand for fish oil capsules, very large quantities of fish would have to be caught and processed, which contributes to overfishing and disturbs the ecological balance in the oceans. Traces of PCBs and dioxins can also be detected in finished fish oil capsules. These have no effect at low intake levels, but at high doses they can have harmful effects on people. So be sure to choose high-quality fish oil capsules when you buy them.

Positive effects of omega-3

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

Protection against arrhythmias
Stabilization of atherosclerotic plaques and thus prevention of plaque rupture, which can lead to 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 inflammatory mediators
Lowering of triglyceride levels
Evidence that the risk of dementia or depression may be reduced

Side effects of omega-3

But side effects are also known.

Side effects of omega-3 medications

There are also medications that contain ethyl esters of omega-3 fatty acids; Icosapent ethyl is named as an ingredient and can be prescribed for people with elevated blood lipid levels. Here the side effects are described more specifically. In addition to nausea, abdominal pain, inflammation of the mucous membranes in the gastrointestinal tract and taste disturbances, dizziness is also listed. For a drug that was temporarily unavailable in Germany due to a price dispute, bleeding, edema, atrial fibrillation, constipation, muscle and bone pain, gout and skin rashes were known as undesirable 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 depended on the dose of omega-3 fatty acids that participants took in the relevant studies. It was shown that the risk of developing atrial fibrillation was highest with an administered daily dose of 4 g.

Side effects of omega-3 supplements

With omega-3 products sold as dietary supplements, fishy burps and bad breath are often reported, less commonly nausea and stomach or intestinal problems.

As mentioned above, medications containing omega-3 fatty acids were associated with increased atrial fibrillation. In the corresponding statement the Federal Institute for Risk Assessment (BfR) specifically addresses dietary supplements:

Dietary supplements containing omega-3 fatty acids are offered, for example, in the form of fish oil capsules and sometimes contain doses similar to medicines. Unlike medicines, supplements are freely available on the market and can be taken over long periods without medical supervision. Possible adverse health effects can therefore be more easily overlooked.

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

The omega-3 index

The so-called omega-3 index denotes the share of omega-3 fatty acids of the 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 omega-3 index averages 4 percent there are 148 cases of sudden cardiac death per 100,000 people. In Japan the omega-3 index averages 11 percent sudden cardiac death affects only 7.8 out of 100,000 people.

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

However, it's not only the amount of omega-3 fatty acids you eat that matters. Our diet generally contains relatively large amounts of omega-6 fatty acids, which act as counterparts to omega-3s. The breakdown of the omega-6 fatty acid linoleic acid to arachidonic acid requires the same enzyme system as the conversion of the omega-3 alpha-linolenic acid 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's important to pay attention to a balanced omega-6 to omega-3 ratio. The German Nutrition Society (DGE) recommends a maximum ratio of 5:1. That means no more than five times as much omega-6 as omega-3. Currently the ratio is usually about 8:1.

To get a sufficient amount of 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 capsules is repeatedly questioned.

If you change your diet accordingly, eat fish and prefer valuable plant oils (for example flax, microalgae, chia, camelina or hemp oil for cold dishes and rapeseed oil for cooking and cold use) over unhealthy saturated animal fats, you benefit in several ways. On one hand you take in omega-3 fatty acids in a form that is likely more useful, and on the other hand a meal of less healthy red meat is replaced by the healthier fish 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 (in limited amounts) into omega-3 fatty acids. Of course, whole flaxseed is also high in alpha-linolenic acid and, when ground and taken with sufficient liquid, is well absorbed. Hemp oil and walnuts or walnut oil are also good plant sources of alpha-linolenic acid. Other, currently more exotic sources are 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 discussing the benefits of omega-3 fatty acids you will usually also hear about omega-6 fatty acids and the need to keep a balanced ratio. The recommendation is 5:1. That means you should consume no more than five times as many omega-6 as omega-3 fatty acids. That's hard if you don't know what they are and which foods contain them.

Omega-6 fatty acids are also polyunsaturated fats. Some are essential and therefore must be supplied in the diet because the body cannot produce them on its own.

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

Functions of omega-6 fatty acids

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

The arachidonic and gamma-linolenic acids formed from linoleic acid have more specific roles. Arachidonic acid is not only a component of cell membranes it also serves as the basis for building tissue hormones (eicosanoids). These produce free radicals that are necessary to defend against harmful substances. However, they also promote inflammatory processes in the body and cause blood vessel constriction. 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 don't have to worry much about getting enough.

Linoleic acid is present in large amounts in oils such as safflower and sunflower oil. It is also found in meat and meat products from conventional farming because farm animals are often fed linoleic acidrich feed.

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

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

So omega-6 fatty acids are also important for the body. However, an excess is more likely to 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 03/2024).

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.