Krill oil is derived from Antarctic krill (Euphausia superba), tiny crustaceans that are among the most abundant organisms on Earth. Unlike fish oil, where EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are carried predominantly as triglycerides, krill oil delivers these omega-3 fatty acids primarily as phospholipids — specifically phosphatidylcholine-bound EPA and DHA. Krill oil also contains astaxanthin (as a natural preservative) and choline.
The key commercial claim for krill oil is that phospholipid-bound omega-3s are more efficiently absorbed into cell membranes than triglyceride-form omega-3s from fish oil, allowing the same cardiovascular and brain health benefits to be achieved at a lower dose of EPA+DHA — and therefore a smaller capsule size. This is the foundation of the premium pricing krill oil commands in Irish health shops.
The biological basis for the absorption advantage claim is mechanistically plausible. Phospholipid-bound fatty acids can be absorbed directly by intestinal epithelial cells via a different pathway than triglycerides, which require more extensive enzymatic processing (lipase activity, micelle formation) before absorption. Phospholipid-bound EPA/DHA may therefore absorb more rapidly and be incorporated into plasma phospholipids more directly — the same form in which they naturally occur in cell membranes.
Multiple pharmacokinetic studies have compared plasma omega-3 levels after krill oil vs fish oil supplementation at equivalent EPA+DHA doses. Results have been mixed. A 2011 study by Ulven et al. (Lipids) found that krill oil produced similar increases in plasma EPA and DHA levels as fish oil at equivalent EPA+DHA doses, suggesting comparable bioavailability rather than a dramatic advantage. A 2013 study by Ramprasath et al. found higher plasma EPA incorporation with krill oil compared to fish oil at a lower krill oil dose — supporting the absorption advantage claim. The data is genuinely inconsistent.
Neptune Krill Oil (NKO®) is a patented extract with its own clinical research portfolio. Bunea et al. (2004) compared NKO® (2–3 g/day) vs fish oil (3 g/day) vs placebo in 120 patients with high cholesterol and triglycerides over three months. Results showed that NKO® produced greater reductions in total cholesterol (−13% vs −9.4% for fish oil), LDL (−32% vs −4.6%), and triglycerides (−11.9% vs −4.6%), while increasing HDL more than fish oil. These results are striking — but this single study has not been robustly replicated with NKO® specifically, and it was conducted by researchers with NKO® industry connections.
A 2014 systematic review by Kwantes & Grundmann found that the overall evidence for krill oil in lipid management was promising but insufficient to draw firm clinical conclusions, citing small study sizes and heterogeneous methodology across trials.
| Claim | Evidence Level | Source |
|---|---|---|
| Phospholipid-bound omega-3 has distinct absorption pathway | Strong (mechanistic) | Established lipid biochemistry |
| Superior EPA/DHA bioavailability vs fish oil | Inconsistent | Mixed pharmacokinetic results (Ulven 2011; Ramprasath 2013) |
| Reduces LDL and cholesterol (NKO® data) | Limited | Bunea et al. 2004 — single industry-linked trial |
| Contains choline and astaxanthin as bonus | Confirmed (compositional) | Analytical studies of krill oil composition |
| Better than fish oil for brain health | No comparative RCT evidence | Theoretical based on DHA phospholipid chemistry |
Beyond the omega-3 phospholipid debate, krill oil contains two components absent from standard fish oil:
Choline: Krill oil provides meaningful amounts of choline (as phosphatidylcholine), which is an essential nutrient involved in neurotransmitter synthesis, liver function, and cell membrane integrity. Many people in Ireland have insufficient dietary choline intake. This represents a genuine nutritional advantage of krill oil over fish oil.
Astaxanthin: Natural astaxanthin at low concentrations serves as an antioxidant, protecting the oil from oxidation and potentially providing independent benefit (see our Astaxanthin Evidence Review).
Typical doses of krill oil in Irish health stores are 500 mg–2 g per day. Because of the phospholipid delivery claim, some manufacturers suggest that 500–1,000 mg krill oil delivers equivalent benefits to 1,000–2,000 mg fish oil — though this is not definitively proven. Take with a meal containing fat. Krill oil capsules are smaller than fish oil capsules and do not typically cause the "fish burps" associated with standard fish oil.
For most people, the choice between krill and fish oil comes down to cost, tolerance, and secondary nutritional goals. Fish oil provides higher EPA+DHA per gram at lower cost. Krill oil provides phospholipid omega-3, choline, and astaxanthin in a smaller capsule with no reflux — at approximately 3–5x the price for equivalent EPA+DHA content. If you value the choline component or struggle with fish oil tolerance, krill oil is a reasonable premium. If you primarily want EPA+DHA at the most evidence-backed doses for cardiovascular health, high-quality fish oil remains more cost-effective.
Krill oil has the same interaction considerations as fish oil: mild antiplatelet effect at higher doses, so caution with anticoagulant medication. Discuss with GP if on warfarin, aspirin, or other blood thinners. People with shellfish allergies should avoid krill oil. No other significant drug interactions have been documented.
Krill oil is a legitimate omega-3 supplement with some meaningful advantages over standard fish oil — primarily in tolerance, choline content, and natural astaxanthin. The absorption advantage over fish oil is real in mechanism but inconsistent in comparative pharmacokinetic studies. The NKO® lipid trial data is compelling but from a limited evidence base. For most people seeking omega-3 supplementation, both fish oil and krill oil are effective — krill oil justifies its premium price primarily for those who want choline, dislike fish oil side effects, or prefer a smaller capsule.