Fish oil
Content by: OpenSupplement Editorial Team | Medical review: pending | Last updated: April 13, 2026
TL;DR
Concentrated source of Omega-3 fatty acids EPA and DHA
High evidence for heart health (triglycerides) and reducing inflammation
Moderate evidence for cognitive health and macular degeneration
Strongest benefits come from high-dose EPA (as seen in the REDUCE-IT trial)
Well-tolerated; potential for 'fishy burps' and mild blood thinning
Cost: ~$15-25/month
Best for: Heart health, high triglycerides, chronic inflammation, eye health
What it is
Fish oil is derived from the tissues of oily fish (anchovies, sardines, mackerel). Its benefits come from two long-chain omega-3 fatty acids: EPA (Eicosapentaenoic acid) and DHA (Docosahexaenoic acid). EPA is primarily anti-inflammatory, while DHA is a major structural component of the brain and retina.
In the modern diet, we consume far too many Omega-6s (vegetable oils) and not enough Omega-3s. This imbalance drives systemic inflammation. Fish oil helps restore the balance, acting like 'biological grease' for the cardiovascular and nervous systems.
What the research says
The evidence for heart health is massive. Triglycerides. It is FDA-approved for lowering very high triglycerides. The REDUCE-IT Trial. This landmark study showed that high-dose, purified EPA (4g daily) reduced the risk of major cardiovascular events by 25% in high-risk patients. Blood Pressure. Meta-analyses show a modest reduction in blood pressure, especially in those with existing hypertension. Note. It is better at preventing a second heart attack than preventing the first one in healthy people. [1][2]
Fish oil helps manage the inflammatory side of metabolic syndrome. Inflammation. It reduces markers like C-reactive protein (CRP). Insulin. While it doesn't always lower blood sugar directly, it may improve insulin sensitivity in the liver. Verdict. A foundational supplement for anyone with 'metabolic' issues, even if it's not a primary glucose-lowering tool. [4]
The brain is roughly 60% fat, and much of that is DHA. Prevention. Observational studies show that people who eat more fish have lower rates of Alzheimer's. Trials. Clinical trials (like the MAPT study) show that while fish oil doesn't reverse dementia, it may slow decline in those who are in the very early stages of memory loss and have low Omega-3 levels. It is a 'brain maintenance' nutrient. [5]
DHA is concentrated in the retina. Evidence. Large observational studies (like the Blue Mountains Eye Study) found that regular fish consumption or Omega-3 intake was associated with a lower risk of both early and late-stage AMD. AREDS2. While the AREDS2 trial didn't find that adding fish oil helped more than the core formula, many ophthalmologists still recommend it for general retinal health and dry eye syndrome. [3]
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Fish oil on Amazon
Safety
Generally very safe. At high doses (3g+), it may have a mild blood-thinning effect. The most common complaints are GI upset and fishy aftertaste. Quality is paramount: look for IFOS-certified oils to ensure no mercury, PCBs, or rancidity.
Interactions
- Blood Thinners: May increase bleeding risk with Warfarin or Aspirin at high doses.
- Contraceptives: May interfere with the triglyceride-lowering effect of fish oil.
Dosing
For Heart Health: 1,000-2,000 mg of combined EPA/DHA daily. For Triglycerides: 2,000-4,000 mg. Form: Look for the 'Triglyceride' form for better absorption than the 'Ethyl Ester' form. Tip: Keep it in the fridge to prevent rancidity.
Cost
Moderate. $15-25 for a high-quality, high-dose month supply.
The bottom line
Fish oil is a foundational 'essential' supplement. It's one of the few things that almost everyone can benefit from, particularly for heart and brain longevity.
References
- Bhatt DL, Steg PG, Miller M, et al. Cardiovascular Risk Reduction with Icosapent Ethyl for Hypertriglyceridemia. N Engl J Med. 2019;380(1):11-22.
- Abdelhamid AS, Brown TJ, Brainard JS, et al. Omega-3 fatty acids for the primary and secondary prevention of cardiovascular disease. Cochrane Database Syst Rev. 2020;3(3):CD003177.
- Age-Related Eye Disease Study 2 Research Group. Lutein + zeaxanthin and omega-3 fatty acids for age-related macular degeneration: the Age-Related Eye Disease Study 2 (AREDS2) randomized clinical trial. JAMA. 2013;309(19):2005-2015.
- Eslick GD, Howe PR, Smith C, et al. Benefits of fish oil supplementation in hyperlipidemia: a systematic review and meta-analysis. Int J Cardiol. 2009;136(1):4-16.
- Zhang Y, Chen J, Qiu J, et al. Intakes of fish and polyunsaturated fatty acids and mild-to-severe cognitive impairment risks: a dose-response meta-analysis of 21 cohort studies. Am J Clin Nutr. 2016;103(2):330-340.
Sources for this page include published meta-analyses, systematic reviews, and NIH dietary supplement fact sheets. All claims reflect the evidence as of early 2026.
This is not medical advice. Consult your healthcare provider before starting any supplement, especially if you take medications.