Fish Oil vs. Omega-3s: What's the Difference?
- Adriano dos Santos
- Jun 5
- 5 min read
Nutritional science continues to explore the role of specific fats in maintaining cardiovascular health. Among these, omega-3 fatty acids derived from marine sources have emerged as a focus of extensive research and public interest.
Table of Contents:
Fish Oil ≠ Omega-3s
Do Fish Oil Supplements Actually Work
Meta-Analysis Insights
Cohort Study Findings
How Fish Oil Works
Environment and Sustainability
When Is Fish Oil Supplementation Appropriate
About me
I am Adriano dos Santos, MSc, rNutr, IFMCP, MBOG, RSM, a Functional Registered Nutritionist, Sleep Medicine & Microbiome Researcher and Educator.
Introduction
Fish oil and omega-3 fatty acids are often mentioned in the same breath, especially when talking about heart health. But while they’re related, they’re not identical. Fish oil is a source of omega-3s, which include EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), both known for their anti-inflammatory and cardioprotective effects. However, the scientific community still debates how effective fish oil supplements really are in preventing or treating cardiovascular diseases.
Fish Oil ≠ Omega-3s
Although fish oil contains omega-3s, not all omega-3s come from fish oil. Omega-3 fatty acids can be extracted from various sources, including marine fish, krill, microalgae, and even plant seeds. Fish oil supplements, however, typically refer to omega-3s derived directly from marine fish such as anchovies, sardines, and mackerel.
The composition and concentration of EPA and DHA vary significantly depending on the source. Advances in extraction technologies now allow the recovery of high-purity omega-3s from fish processing by-products like heads, viscera, and skin. This innovation enhances the sustainability of fish oil production by utilizing materials that would otherwise go to waste. Still, while production methods have evolved, the clinical effectiveness of these supplements continues to be an active area of research (Gabriele Alfio V. et al., 2021).
Do Fish Oil Supplements Actually Work?
This question has been examined in both clinical trials and large population studies, offering a more complete picture of fish oil’s effects on heart health.
Meta-Analysis Insights
One meta-analysis reviewed multiple clinical trials involving a large number of participants and found that omega-3 supplements may offer a small but meaningful benefit in reducing cardiovascular-related deaths. The researchers also applied a technique to assess whether more trials were needed and concluded that the current evidence was strong enough to suggest that additional studies would be unlikely to change the outcome (Cabiddu M.F. et al., 2020). While the effect is modest, omega-3s may play a helpful role in supporting cardiovascular health, particularly for those with existing conditions.
Cohort Study Findings
A large prospective study following hundreds of thousands of adults in the UK provided a more nuanced perspective. It found that fish oil supplements may not be helpful for everyone. Among people without existing heart conditions, regular use was linked to a higher chance of developing atrial fibrillation. However, in individuals who already had heart rhythm problems, fish oil seemed to help reduce the risk of more serious cardiovascular events and death (Chen G. et al., 2024).
In summary, fish oil supplements are not a universal solution. While they may offer benefits for individuals with existing cardiovascular conditions, their use among otherwise healthy individuals may be unnecessary or potentially associated with certain risks.
How Fish Oil Works (When It Works)
The beneficial effects of omega-3 fatty acids are attributed to several physiological mechanisms. These include their ability to reduce inflammation by promoting the production of specialized pro-resolving mediators such as resolvins and protectins, which help resolve inflammatory processes. Omega-3s also contribute to improved endothelial function, lower the risk of thrombosis by reducing platelet aggregation, and support the regulation of lipid metabolism, particularly through the reduction of triglyceride levels. Additionally, they may stabilize cardiac electrical activity, potentially lowering the risk of arrhythmias (Liao J. et al., 2022).
These mechanisms provide insight into why omega-3 supplementation may be more effective in individuals with existing cardiovascular conditions, where the physiological systems are already compromised and thus more responsive to intervention.
What About the Environment and Sustainability?
Fish oil production raises important environmental concerns, particularly due to the overfishing of small pelagic species such as anchovies, which are a primary source of omega-3s. Unsustainable fishing practices can disrupt delicate marine ecosystems, especially when targeted species also play a vital role in the diets of predators in those systems (Watters G. et al., 2020).
To address these concerns, alternative sources of omega-3s are gaining attention. Advances in extraction technology now allow for the recovery of high-purity omega-3s from fish waste, including byproducts like heads, viscera, and skin, contributing to a more sustainable production model. Algal-based omega-3s also offer an environmentally friendly, plant-based option that does not rely on marine animal harvest (Gabriele Alfio V. et al., 2021).
When Is Fish Oil Supplementation Appropriate?
Fish oil supplementation is most appropriate in cases of diagnosed cardiovascular disease, including post heart attack or heart failure, where high doses, especially those rich in EPA or DHA, have been shown to improve heart function and reduce prothrombotic activity in the blood (Sharman A. et al., 2025). It may also be beneficial for individuals at elevated risk of sudden cardiac death, as higher circulating levels of EPA and DHA are linked with significantly reduced risk (Young Kim J. et al., 2024).
Caution is warranted when using fish oil for general wellness in otherwise healthy individuals, as the evidence supporting broad preventive use without specific cardiovascular markers or symptoms remains inconsistent (Sharman A. et al., 2025). Additionally, supplementation in people with a history of arrhythmias like atrial fibrillation should be closely supervised by a healthcare provider, given the complex and not fully understood relationship between omega-3s and cardiac electrical activity (Young Kim J. et al., 2024).
Conclusion
The difference between fish oil and omega-3s is not only in their origin but also in their potential health effects. Omega-3s derived from fish oil may offer benefits for certain individuals, particularly those with existing cardiovascular disease. However, for healthy individuals, the advantages appear to be limited, and in some cases, there may even be associated risks.
The effectiveness of fish oil also depends on factors such as formulation, dosage, and the individual's health profile. Therefore, fish oil should not be considered a one-size-fits-all solution. Rather, it is a targeted intervention that may be helpful for some, but not necessary or appropriate for everyone.
References:
Watters G., Hinke J., Reiss C. (2020). Long-term observations from Antarctica demonstrate that mismatched scales of fisheries management and predator-prey interaction lead to erroneous conclusions about precaution. Nature. https://doi.org/10.1038/s41598-020-59223-9
Gabriele Alfio V., Manzo C., Micillo R. (2021). From Fish Waste to Value: An Overview of the Sustainable Recovery of Omega-3 for Food Supplements. MDPI. Molecules. doi: 10.3390/molecules26041002
Cabiddu M.F., Russi A., Appolloni L., Mengato D., Chiumente M. (2020). Omega-3 for the prevention of cardiovascular diseases: meta-analysis and trial-sequential analysis. BMJ Journals. doi: 10.1136/ejhpharm-2020-002207
Liao J., Xiong Q., Yin Y., Ling Z., Chen S. (2022). The Effects of Fish Oil on Cardiovascular Diseases: Systematical Evaluation and Recent Advance. Frontiers. doi: 10.3389/fcvm.2021.802306
Chen G., Qian Z., Zhang J., Zhang S., Zhang Z., Vaughn M., Aaron H., Wang C., Lip G., Lin H. (2024). Regular use of fish oil supplements and course of cardiovascular diseases: prospective cohort study. BMJ Journals. doi: 10.1136/bmjmed-2022-000451
Sharman A., Zhou R., Pugh J., Close G., Fisk H., Calder P., Yaqoob P. (2025). High-dose fish oil supplements are more effective than oily fish in altering the number and function of extracellular vesicles in healthy human subjects: a randomised, double-blind, placebo-controlled, parallel trial. British Journal of Nutrition. https://doi.org/10.1017/S0007114525000625
Young Kim J., Joyce Kong S.Y., Jung E., Soo Cho Y. (2024). Omega-3 Fatty Acids as Potential Predictors of Sudden Cardiac Death and Cardiovascular Mortality: A Systematic Review and Meta-Analysis. MDPI. Journal of Clinical Medicine. https://doi.org/10.3390/jcm14010026
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