Omega-3 Fish Oils: What They Are, Where to Get Them, and What Science Says

This update explains omega-3 fatty acids EPA and DHA, primary food sources (oily fish), and the current clinical view: seafood is the preferred source, supplements can lower triglycerides, and high-purity prescription EPA at 4 g/day showed cardiovascular benefit in a high-risk trial. Dosage and use should follow clinical guidance, and product quality matters.

What are omega-3 fatty acids?

Omega-3s are long-chain polyunsaturated fatty acids that act as structural and signaling molecules in the body. The two most important marine omega-3s are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Both occur naturally in oily fish and are the primary active ingredients in fish-oil supplements.

EPA and DHA - roles at a glance

EPA participates in inflammation and blood-lipid regulation. DHA concentrates in the brain and retina and supports neural and visual development.

Food sources and supplements

Fatty fish such as salmon, mackerel, herring, sardines, and trout are rich in EPA and DHA. Public health agencies generally recommend eating about two servings (roughly 8 ounces) of seafood per week as part of a healthy diet to provide omega-3s and other nutrients.

Fish-oil supplements come as over-the-counter capsules (mixed EPA+DHA) or as prescription products. Prescription omega-3 formulations are purified and standardized for dose and composition; one prescription formulation is high-purity EPA (icosapent ethyl). Quality matters: look for third-party testing for purity and potency and follow label guidance.

Health effects and the evidence

Cardiovascular disease: omega-3s lower blood triglyceride levels. For people with high triglycerides, higher doses (typically 2-4 g/day of EPA+DHA) can substantially reduce triglyceride concentrations when taken under medical supervision.

Clinical trial evidence on hard cardiovascular outcomes is mixed. A large trial of a purified EPA product at 4 g/day reported reduced major cardiovascular events in high-risk patients on statin therapy, while some other trials of combined EPA+DHA formulations did not show the same benefit.¹

General heart-health guidance emphasizes getting omega-3s from seafood when possible and using supplements under a clinician's advice when needed.

Brain, eye, and pregnancy considerations: DHA is important for fetal brain and retinal development. Pregnant and breastfeeding people are advised to include low-mercury seafood choices or discuss supplements with their clinician.²

Inflammation and skin: EPA and DHA can modulate inflammatory processes. Some people report symptom improvements in inflammatory skin conditions, but responses vary and evidence is not uniform.

Safety and practical advice

• Follow dosage recommendations for specific conditions and consult a clinician before high-dose use.

• Be aware of potential interactions (for example, with blood thinners) and of contaminants in some seafood; choose low-mercury fish and tested supplements.

• Prefer whole-food sources when practical. Use supplements to fill gaps or to treat medically defined conditions under supervision.

Takeaway

Omega-3s (EPA and DHA) are important dietary fats with clear triglyceride-lowering effects and roles in brain and eye health. Aim to meet recommendations through seafood first; use supplements or prescription products when medically indicated and supervised by a clinician.

1. Confirm current public health recommendation for seafood intake (two servings/8 ounces per week) source and phrasing.
2. Verify guideline statement and exact recommendation for 1 g/day EPA+DHA for people with established coronary heart disease from major cardiology organizations (e.g., AHA).
3. Confirm details of clinical trial evidence: REDUCE-IT (4 g/day icosapent ethyl reduced major cardiovascular events) and contrasting trials of combined EPA+DHA (e.g., STRENGTH) for accuracy and publication details.
4. Verify pregnancy guidance on DHA intake and low-mercury seafood recommendations from current obstetrics/nutrition authorities.