Fish Oil (Omega-3 EPA/DHA)
Essential fatty acids critical for heart, brain, and whole-body health
Also known as: Omega-3 • EPA/DHA • Fish Oil • Omega-3 Fatty Acids
Overview
Fish oil is the most popular source of the omega-3 fatty acids EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), which are essential fats that the human body cannot produce on its own. These long-chain polyunsaturated fatty acids play fundamental roles in cell membrane structure, brain function, cardiovascular health, and the resolution of inflammation. The modern Western diet is dramatically skewed toward omega-6 fatty acids (from seed oils and processed foods), with typical omega-6 to omega-3 ratios of 15:1 to 20:1, compared to the evolutionary ratio of approximately 1:1 to 4:1. This imbalance drives chronic low-grade inflammation, which underlies many modern diseases. Supplementation with EPA and DHA helps restore a healthier omega-6 to omega-3 ratio and has been shown to reduce triglycerides, lower blood pressure, reduce inflammation, support brain health, and improve mood. The American Heart Association recommends at least two servings of fatty fish per week, and supplementation for those who do not meet this through diet.
Key Benefits
Cardiovascular Health
Fish oil's cardiovascular benefits are among the most well-established in nutrition science. EPA and DHA reduce triglycerides by 15–30%, lower blood pressure, reduce resting heart rate, improve arterial function, and have anti-arrhythmic properties. The REDUCE-IT trial showed that high-dose EPA (4g/day) reduced cardiovascular events by 25%.
Brain Health & Cognitive Function
DHA comprises approximately 40% of the polyunsaturated fatty acids in the brain. Adequate omega-3 intake supports neuronal membrane fluidity, neurotransmitter function, and neuroplasticity. Higher omega-3 levels are associated with larger brain volumes and reduced cognitive decline with aging.
Anti-Inflammatory Effects
EPA and DHA are precursors to specialized pro-resolving mediators (SPMs) — molecules that actively resolve inflammation rather than just suppressing it. This makes omega-3s fundamentally different from anti-inflammatory drugs. Regular supplementation reduces CRP, IL-6, and TNF-alpha levels.
Mood & Depression
Meta-analyses consistently show that omega-3 supplementation, particularly EPA-dominant formulas, reduces symptoms of depression. The effect size is comparable to some antidepressant medications. EPA appears to be more effective than DHA for mood benefits, with optimal doses around 1–2 g EPA per day.
Joint Health
Omega-3s reduce joint stiffness, tenderness, and pain in people with rheumatoid arthritis and osteoarthritis. Multiple studies show that fish oil supplementation can reduce the need for NSAIDs. Benefits typically appear after 2–3 months of consistent supplementation.
Dosage & How to Take
The general recommendation is 1,000–3,000 mg of combined EPA+DHA daily. Note: this refers to the actual EPA+DHA content, not the total fish oil amount. A standard 1,000 mg fish oil capsule typically contains only 300 mg of combined EPA+DHA, so you may need multiple capsules.
| Purpose | Dose | Notes |
|---|---|---|
| General health maintenance | 1,000 mg EPA+DHA daily | Minimum effective dose for most benefits |
| Heart health / triglyceride reduction | 2,000–4,000 mg EPA+DHA daily | Higher doses needed for significant triglyceride reduction |
| Depression / mood support | 1,000–2,000 mg EPA daily | EPA-dominant formulas (2:1 or 3:1 EPA:DHA) preferred |
| Joint pain / inflammation | 2,000–3,000 mg EPA+DHA daily | Allow 2–3 months for full anti-inflammatory effects |
| Brain health / cognitive support | 1,000–2,000 mg DHA daily | DHA-dominant formulas preferred for brain-specific benefits |
Best Time to Take
Take with the largest meal of the day (containing fat) for optimal absorption. Splitting into 2 doses (morning and evening meals) may improve tolerance at higher doses.
With or Without Food
Always take with a fat-containing meal. Absorption of EPA and DHA increases by up to 300% when taken with dietary fat compared to on an empty stomach.
Forms & Bioavailability
| Form | Absorption | Best For | Notes |
|---|---|---|---|
| Triglyceride (TG) Form Fish Oil | Highest | Best overall absorption | Natural form found in fish. 70% better absorbed than ethyl ester form. |
| Ethyl Ester (EE) Form | Moderate | Budget option, concentrated formulas | Most common form in supplements. Requires more processing by the body. |
| Krill Oil | High | Those who want phospholipid-bound omega-3s + astaxanthin | Contains phospholipid-bound EPA/DHA plus astaxanthin antioxidant. Lower total EPA/DHA per capsule. |
| Algal Oil (Vegan) | High | Vegans, vegetarians, fish allergy | DHA-rich (some also contain EPA). Sustainable, no ocean contaminant concerns. |
| Cod Liver Oil | High | Those wanting omega-3s + vitamins A and D | Contains naturally occurring vitamins A and D. Watch for vitamin A toxicity at high doses. |
Side Effects & Safety
Common
- Fishy burps/aftertaste (reduced with enteric-coated capsules or taking with meals)
- Mild GI discomfort at high doses
Rare
- Increased bleeding time at very high doses (>3g/day)
- Mild loose stools
Contraindications
- Fish/shellfish allergy (use algal oil instead)
- Blood clotting disorders (consult physician at high doses)
- Scheduled surgery (some doctors recommend stopping 1–2 weeks before)
Interactions
Fish oil has mild blood-thinning effects. At high doses (>3g/day), may increase bleeding risk. Monitor INR if on warfarin.
Additive blood pressure lowering effect. May allow for lower medication doses. Monitor blood pressure.
Synergistic — Vitamin E protects omega-3s from oxidation. Many quality fish oils include vitamin E.
Fish oil enhances vitamin D absorption. Complementary pairing.
Scientific Research
REDUCE-IT Trial
Landmark trial of 8,179 patients found that 4g/day of pure EPA (icosapent ethyl) reduced cardiovascular events by 25% compared to placebo, including a 20% reduction in cardiovascular death.
Omega-3 and Depression
Meta-analysis of 26 RCTs found that omega-3 supplementation had a significant antidepressant effect, with EPA-predominant formulas (≥60% EPA) showing the strongest benefits.
Omega-3 and Brain Volume
Study of 2,183 dementia-free participants found that higher omega-3 index was associated with larger hippocampal volumes and better abstract reasoning, suggesting a protective effect against brain aging.
Fish Oil Form Comparison
Head-to-head comparison showed that triglyceride-form fish oil had 70% greater bioavailability than ethyl ester form, as measured by EPA and DHA blood levels.
Food Sources
Frequently Asked Questions
Medical Disclaimer
This content is for educational and informational purposes only and is not intended as medical advice. Always consult with a qualified healthcare professional before starting any supplement regimen, especially if you have pre-existing health conditions or are taking medications. The statements on this page have not been evaluated by the Food and Drug Administration.