Omega-3 fatty acids – impact on heart health

Omega-3 fatty acids belong to the group of fats, i.e. compounds consisting mainly of carbon, hydrogen and oxygen atoms, which perform energy and structural functions. Within omega-3, the three most important forms are: ALA (alpha-linolenic acid), EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), which differ in the length of their carbon chains and the number of double bonds, and thus also in their functions. Omega-3 fatty acids, especially the long-chain EPA and DHA, are widely studied for their effects on heart health.

1. Structure of omega-3 fatty acids
2. Omega-3 diversity
3. Research on omega-3
4. Heart health disorders
5. Omega-3 and the heart

Structure of omega-3 fatty acids

Biologically active fats occur mainly in the form of triglycerides, which consist of one glycerol molecule and three fatty acid residues. Fatty acids can be saturated (without double bonds) or unsaturated (with at least one double bond). Omega-3 is a type of polyunsaturated fatty acid characterised by the presence of the first double bond at the third carbon atom from the methyl end of the molecule (known as omega).

Their structure, a long carbon chain with several double bonds, gives them flexibility and affects the fluidity of cell membranes. Alpha-linolenic acid (ALA) has 18 carbon atoms and 3 double bonds, eicosapentaenoic acid (EPA) has 20 carbon atoms and 5 double bonds, while docosahexaenoic acid (DHA) consists of 22 carbon atoms and contains 6 double bonds.

Omega-3 diversity

Although omega-3 fatty acids include both alpha-linolenic acid (ALA) and the long-chain derivatives EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), it is EPA and DHA that dominate clinical and experimental studies as the most biologically active forms with the greatest physiological significance.

This is primarily due to their direct involvement in anti-inflammatory, neuroprotective and structural pathways, especially in the context of brain, retina and cell membrane function. Although ALA can be converted into EPA and DHA in the human body, this process occurs with very low efficiency, reaching only a few percent, which limits its importance as an effective source of these acids.

Research on omega-3

EPA and DHA are found mainly in oily sea fish, fish oils and krill oils, while ALA comes primarily from plant products such as linseed, chia seeds, walnuts and their oils. Providing EPA and DHA in the daily diet can be problematic for several reasons: fish is not commonly consumed in many countries due to its taste, smell, price, limited availability or concerns about environmental contamination, as well as food allergies and vegetarian or vegan preferences.

"Low levels of omega-3 fatty acids are associated with sleep problems in children and obstructive sleep apnoea in adults. Low DHA levels are also linked to lower levels of the hormone melatonin, which helps you fall asleep." Agata Bugorska - IFAA Trainer

This is one of the reasons why intervention and clinical studies focus mainly on EPA and DHA. They are easier to standardise, precisely dose and subject to quality control, which makes them much more convenient and reliable from a scientific research perspective. ALA is more common in the average diet, making it more difficult to isolate the effects of additional supplementation.

Heart health disorders

The most common heart disorders include ischaemic heart disease, hypertension, heart failure, arrhythmias and valve defects. Ischemic heart disease develops as a result of atherosclerosis, i.e. narrowing of the coronary arteries due to lipid deposits and inflammation, which limits the supply of oxygen to the heart muscle. Hypertension often results from poor diet, excessive salt intake, obesity, physical inactivity and chronic stress, leading over time to vascular damage and left ventricular hypertrophy.

The problem and consequences of heart failure

Heart failure, a condition in which the heart is unable to pump enough blood, can be the result of untreated high blood pressure, heart attack, cardiomyopathy or structural defects. Arrhythmias, such as atrial fibrillation, are often associated with age, hypertension, a history of heart disease or electrolyte disturbances. Valve defects, both congenital and acquired, can result from infection, autoimmune diseases or degenerative processes, leading to impaired blood flow and cardiac overload.

General recommendations for omega-3 dosage in the diet depending on health status

Omega-3 and the heart

Analyses of dozens of studies involving hundreds of thousands of participants have shown that EPA and DHA supplementation may reduce the risk of mortality from coronary heart disease and the number of coronary incidents, although it does not significantly affect overall mortality, strokes or the incidence of arrhythmias. Higher blood concentrations of omega-3, especially EPA and DHA, were significantly associated with a lower risk of coronary heart disease (CHD) in prospective and retrospective studies, and patients with CHD had lower levels of these acids compared to healthy individuals.

Omega-3 Index

Of particular importance is the so-called Omega-3 Index, i.e. the percentage of EPA and DHA in erythrocytes, which at values below 4% was associated with the highest risk of death from cardiac causes, while values above 8% correlated with a reduction in this risk by up to 30%.

Lower heart rate thanks to omega-3

Omega-3, especially DHA, also has a negative chronotropic effect, lowering the resting heart rate by an average of about 2–3 beats per minute, which is prognostically significant in the context of cardiovascular mortality. In patients with heart failure, it has been shown that supplementation with EPA and DHA can reduce levels of pro-inflammatory cytokines such as TNF-α and IL-6. Omega-3 can also improve endothelial function, as evidenced by a significant increase in the vascular dilation index (FMD) in patients with CHD after supplementation.

Lower blood pressure and reduced risk of incidents

Population and intervention studies involving people with hypertension and hyperlipidaemia have also shown a moderate, dose-dependent reduction in blood pressure and triglyceride levels, particularly at EPA+DHA doses exceeding 2 g per day.

In contrast, ALA, as a plant form of omega-3, has been shown in studies to have a much weaker and less reproducible effect on the risk of cardiovascular events, and its supply, although potentially associated with a slight reduction in arrhythmia, does not significantly affect overall or cardiovascular mortality.

Sources:

• Abdelhamid, A. S., Brown, T. J., Brainard, J. S., Biswas, P., Thorpe, G. C., Moore, H. J., Deane, K. H., Summerbell, C. D., Worthington, H. V., Song, F., & Hooper, L. (2020). Omega-3 fatty acids for the primary and secondary prevention of cardiovascular disease. The Cochrane database of systematic reviews, 3(3), CD003177. https://doi.org/10.1002/14651858.CD003177.pub5
• Xiao, Y., Chen, Y., Pietzner, A., Elbelt, U., Fan, Z., & Weylandt, K. H. (2024). Circulating Omega-3 Polyunsaturated Fatty Acids Levels in Coronary Heart Disease: Pooled Analysis of 36 Observational Studies. Nutrients, 16(11), 1610. https://doi.org/10.3390/nu16111610
• Harris, W. S., Del Gobbo, L., & Tintle, N. L. (2017). The Omega-3 Index and relative risk for coronary heart disease mortality: Estimation from 10 cohort studies. Atherosclerosis, 262, 51–54. https://doi.org/10.1016/j.atherosclerosis.2017.05.007
• Prokopidis, K., Therdyothin, A., Giannos, P., Morwani-Mangnani, J., Ferentinos, P., Mitropoulos, A., & Isanejad, M. (2023). Does omega-3 supplementation improve the inflammatory profile of patients with heart failure? a systematic review and meta-analysis. Heart failure reviews, 28(6), 1417–1425. https://doi.org/10.1007/s10741-023-10327-0
• Wang, T., Zhang, X., Zhou, N., Shen, Y., Li, B., Chen, B. E., & Li, X. (2023). Association Between Omega-3 Fatty Acid Intake and Dyslipidemia: A Continuous Dose-Response Meta-Analysis of Randomized Controlled Trials. Journal of the American Heart Association, 12(11), e029512. https://doi.org/10.1161/JAHA.123.029512
• Zhang, X., Ritonja, J. A., Zhou, N., Chen, B. E., & Li, X. (2022). Omega-3 Polyunsaturated Fatty Acids Intake and Blood Pressure: A Dose-Response Meta-Analysis of Randomized Controlled Trials. Journal of the American Heart Association, 11(11), e025071. https://doi.org/10.1161/JAHA.121.025071
• Hidayat, K., Yang, J., Zhang, Z., Chen, G. C., Qin, L. Q., Eggersdorfer, M., & Zhang, W. (2018). Effect of omega-3 long-chain polyunsaturated fatty acid supplementation on heart rate: a meta-analysis of randomized controlled trials. European journal of clinical nutrition, 72(6), 805–817. https://doi.org/10.1038/s41430-017-0052-3
• Ibrahim Mohialdeen Gubari M. (2024). Effect of omega-3 fatty acid supplementation on markers of inflammation and endothelial function in patients with chronic heart disease: A systematic review and meta-analysis. Cellular and molecular biology (Noisy-le-Grand, France), 70(6), 171–177. https://doi.org/10.14715/cmb/2024.70.6.26