Fish Oil: What EPA and DHA Actually Do
Fish oil's important components are predominantly the long-chain omega-3 fatty acids EPA and DHA, which become incorporated into cell membranes and influence biological signalling. EPA and DHA give rise to specialised pro-resolving mediators including resolvins, protectins and maresins, so omega-3 fats do not simply switch inflammation off. They influence how inflammatory signalling is regulated and resolved, since inflammation is necessary for immunity, healing and training adaptation. EPA also has a clear clinical effect on lowering elevated triglycerides at higher therapeutic doses, and DHA is an important structural component of neural and retinal tissue. Fish oil does not replace protein, progressive overload, calories or sleep. Krill oil is not automatically superior to fish oil. A capsule advertised as 1,000mg fish oil does not necessarily contain 1,000mg of EPA plus DHA, so the amounts should always be checked and added together.
The important components of fish oil are predominantly the long-chain omega-3 fatty acids EPA and DHA. These fats can become incorporated into cell membranes and influence biological signalling.
EPA, DHA and inflammation
EPA and DHA can give rise to specialised pro-resolving mediators, including resolvins, protectins and maresins.
This is an important distinction. Omega-3 fats do not simply switch inflammation off. Inflammation is necessary for immunity, healing and training adaptation. EPA and DHA can influence how inflammatory signalling is regulated and resolved.
EPA and blood lipids
One of the clearest clinical effects of higher-dose EPA and DHA is lowering elevated triglycerides. Therapeutic doses are different from general supplementation and should not be confused with everyday wellness dosing.
DHA and the nervous system
DHA is an important structural component of neural and retinal tissue and contributes to the physical properties of cell membranes.
What about training
Omega-3 fats are being studied for skeletal-muscle function and healthy ageing. Some research suggests potential benefits for strength or muscle response in selected populations, but results for direct hypertrophy are mixed.
Fish oil does not replace protein, progressive overload, calories or sleep.
Fish oil versus krill oil
Both can provide EPA and DHA. Fish oil commonly provides these fatty acids in triglyceride or ethyl-ester forms. Krill oil contains a meaningful proportion attached to phospholipids and naturally contains astaxanthin.
Krill may deliver omega-3 efficiently at lower absolute doses, but that does not automatically make it superior for long-term health outcomes.
Read the label
A capsule advertised as 1,000mg fish oil does not necessarily contain 1,000mg of EPA plus DHA. Always look for the actual amounts of EPA and DHA and add them together.
For general health, regular fish intake, particularly oily fish, is a strong starting point. Higher supplemental doses should be discussed with a doctor or pharmacist, particularly for people using anticoagulants, preparing for surgery or managing cardiovascular conditions.
The Everest takeaway
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Frequently asked questions
Does fish oil reduce inflammation?
It is more accurate to say EPA and DHA influence how inflammation is regulated and resolved, rather than simply switching inflammation off. Inflammation is necessary for immunity, healing and training adaptation. EPA and DHA can give rise to specialised pro-resolving mediators, including resolvins, protectins and maresins, involved in that regulation.
How do I know if a fish oil supplement actually has enough EPA and DHA?
A capsule advertised as 1,000mg fish oil does not necessarily contain 1,000mg of EPA plus DHA. Always look for the actual amounts of EPA and DHA on the label and add them together, rather than relying on the total fish oil weight stated on the front.
Is krill oil better than regular fish oil?
Both can provide EPA and DHA. Fish oil commonly provides these fatty acids in triglyceride or ethyl-ester forms, while krill oil contains a meaningful proportion attached to phospholipids and naturally contains astaxanthin. Krill may deliver omega-3 efficiently at lower absolute doses, but that does not automatically make it superior for long-term health outcomes.
Sources
- National Institutes of Health, Office of Dietary Supplements (2024). Omega-3 fatty acids: fact sheet for health professionals. ods.od.nih.gov/factsheets/Omega3FattyAcids-HealthProfessional
- Serhan, C.N. (2014). Pro-resolving lipid mediators are leads for resolution physiology. Nature, 510(7503), 92-101. doi.org/10.1038/nature13479
- Ulven, S.M. et al. (2011). Metabolic effects of krill oil are essentially similar to those of fish oil but at lower dose of EPA and DHA, in healthy volunteers. Lipids, 46(1), 37-46. pmc.ncbi.nlm.nih.gov/articles/PMC3168413
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