Omega-6 and omega-3 fats: balance

"Modern people eat 15–20 times more omega-6 than omega-3, and therefore suffer from inflammation" — this claim can be found in many materials about healthy eating. Part of this statement is true, part is a simplification, and some conclusions from it, such as a complete rejection of vegetable oils, have no evidence. The editorial team examined what the balance of polyunsaturated fatty acids actually means.

Omega-6 and omega-3: who is who

Omega-6 and omega-3 are two families of polyunsaturated fatty acids. The name indicates the position of the first double bond from the end of the molecule. The human body cannot synthesise the basic representatives of both families, so linoleic (omega-6) and alpha-linolenic (omega-3) acids are considered essential and must come from food.

From linoleic acid, arachidonic acid is formed in the body, and from alpha-linolenic — eicosapentaenoic (EPA) and docosahexaenoic (DHA). For these conversions both families use the same enzymes, so they compete with each other to a certain extent.

Arachidonic acid, EPA and DHA are incorporated into cell membranes and become precursors of signalling molecules — eicosanoids. Derivatives of arachidonic acid are generally more involved in the development of the inflammatory response, while from EPA and DHA substances are formed that help bring inflammation to a close.

Important: the conversion of alpha-linolenic acid from plant sources into EPA and especially DHA occurs very limitedly in humans. The review by Burdge and Calder (2005) showed that in men only an insignificant fraction is converted to DHA, in women somewhat more. So flax and walnuts do not replace fish as a source of long-chain omega-3.

The ratio: where the idea came from

The idea of the ratio was popularised by Artemis Simopoulos. Her review (2002) noted that in the diet to which humans evolutionarily adapted, the ratio of omega-6 to omega-3 was close to 1:1, whereas in the modern Western diet it is estimated at roughly 15–17:1. The author linked this shift to the spread of chronic inflammatory diseases.

The reasons for the shift are clear: the mass use of sunflower, corn and soybean oils rich in linoleic acid, as well as a decrease in the consumption of fish and products of grass-fed animals. For the Ukrainian diet with its active use of sunflower oil this is especially relevant.

However, modern science treats the ratio more critically. It equally "worsens" both when there is too much omega-6 and when there is too little omega-3, although these situations have different consequences. A person who eats little omega-6 and little omega-3 can have an "ideal" ratio with a deficiency of both.

So many researchers propose to assess the absolute consumption of EPA and DHA or their level in the body, rather than the ratio itself. In practice this means: the main problem for most people is not an excess of omega-6, but a shortage of omega-3.

Are omega-6 harmful

The popular claim that "omega-6 provoke inflammation" rests on the fact that pro-inflammatory eicosanoids are formed from arachidonic acid. However, an increase in the consumption of linoleic acid in humans changes the level of arachidonic acid in tissues little, because its synthesis is tightly regulated.

The scientific council of the American Heart Association (Harris et al., 2009) analysed the data and concluded that consuming omega-6 at a level of 5–10% of the diet's calorie content is associated with a reduction in cardiovascular risk compared with lower consumption. The recommendation to cut omega-6 for the sake of "balance" did not receive support.

Another matter is the quality of the products in which omega-6 "hide". Fast food, chips, deep-fried dishes and confectionery contain a lot of oils, but the problem here is in the overall profile of the products, not in linoleic acid itself.

So the sensible approach is not to fear vegetable oils, but to use various sources of fats: olive, rapeseed, sunflower oils, nuts, seeds and fish — and to limit ultra-processed foods.

The omega-3 index and sources of EPA and DHA

Harris and von Schacky (2004) proposed the omega-3 index — the share of EPA and DHA in the membranes of red blood cells out of all fatty acids. It reflects the consumption of omega-3 over the previous few months. The authors considered a level above 8% to be associated with the lowest cardiovascular risk, and below 4% with the highest.

The European Food Safety Authority (EFSA, 2010) set the adequate intake of EPA and DHA for adults at 250 mg per day. This can be achieved by consuming oily fish 1–2 times a week.

• Oily fish: salmon, mackerel, herring, sardines, anchovies — 1–2 servings a week.
• For those who do not eat fish — fish oil or microalgae oil (for vegetarians and vegans).
• Flaxseed oil, chia seeds and walnuts are sources of ALA, but not a substitute for EPA and DHA.
• For cooking — combine various oils, not limiting yourself to sunflower alone.

When choosing supplements, it is worth paying attention to the content of EPA and DHA specifically in a serving, rather than the total amount of "fish oil". The freshness of the product and the presence of independent quality certificates are also important, since oxidised oils have an unpleasant smell and probably less benefit.

Omega-3 for athletes

Interest in omega-3 in sport is linked to a possible effect on recovery, muscle soreness, the cardiovascular system and the state of the nervous system. The review by Philpott, Witard and Galloway (2019) notes that in some studies omega-3 supplements reduced delayed-onset muscle soreness and helped preserve muscle during periods of inactivity.

At the same time, a direct improvement of sporting results — strength, speed, endurance — was not found in most studies. Omega-3 is rather an element of healthy eating and recovery, not a means of increasing performance.

Studies among athletes show that many of them have a low omega-3 index due to infrequent consumption of fish. For such people a correction of the diet or supplements can be useful, especially in sports with a large training volume and a risk of injuries.

High doses of omega-3 can enhance the action of anticoagulants, cause gastrointestinal upset, and in some studies in people with high cardiovascular risk high doses were associated with more frequent atrial fibrillation. So doses above ordinary dietary ones should be discussed with a doctor.

Editorial conclusions

The ratio of omega-6 to omega-3 in the modern diet is indeed shifted, but the main problem is a shortage of EPA and DHA, not an excess of omega-6.

Vegetable oils with linoleic acid are not a "poison": moderate consumption of omega-6 is associated with reduced cardiovascular risk. Harmful are primarily ultra-processed foods.

The simplest way to improve the balance is to eat oily fish 1–2 times a week or use quality EPA and DHA supplements, guided if necessary by the omega-3 index.

The editorial team also recommends familiarising yourself with our materials about fish oil for athletes, about nutrition for joint health and about nutrition for injuries.

References

1. Simopoulos AP. The importance of the ratio of omega-6/omega-3 essential fatty acids. Biomed Pharmacother. 2002;56(8):365–379.
2. Harris WS, Mozaffarian D, Rimm E, et al. Omega-6 fatty acids and risk for cardiovascular disease: a science advisory from the American Heart Association. Circulation. 2009;119(6):902–907.
3. Harris WS, von Schacky C. The Omega-3 Index: a new risk factor for death from coronary heart disease? Prev Med. 2004;39(1):212–220.
4. Burdge GC, Calder PC. Conversion of alpha-linolenic acid to longer-chain polyunsaturated fatty acids in human adults. Reprod Nutr Dev. 2005;45(5):581–597.
5. EFSA Panel on Dietetic Products, Nutrition, and Allergies. Scientific Opinion on Dietary Reference Values for fats, including saturated fatty acids, polyunsaturated fatty acids, monounsaturated fatty acids, trans fatty acids, and cholesterol. EFSA J. 2010;8(3):1461.
6. Philpott JD, Witard OC, Galloway SDR. Applications of omega-3 polyunsaturated fatty acid supplementation for sport performance. Res Sports Med. 2019;27(2):219–237.