- Krill oil carries most of its omega-3s as phospholipids; fish oil carries them as triglycerides or ethyl esters. NIH says some studies find phospholipid omega-3s somewhat more bioavailable and others don't.
- Every form of EPA and DHA studied raises blood levels significantly. Form is a secondary detail; total DHA per day is the primary one.
- Krill capsules are typically small and contain less EPA+DHA per capsule than concentrated fish oils, so reaching a trial-level DHA dose can take several capsules.
- Compare products by cost per gram of DHA, not cost per bottle or per capsule.
- Krill oil can make sense if you can't tolerate fish oil, want small softgels, or don't mind paying for the format. Shellfish allergy, blood thinners, and upcoming surgery need a clinician's input.
The real difference: what the omega-3 is attached to
EPA and DHA are the same molecules whether they come from anchovies, salmon, algae, or Antarctic krill. What differs is the "carrier" they're packaged on. The NIH Office of Dietary Supplements (ODS) lists the main forms found in supplements:[1]
- Natural triglycerides — the form in unprocessed fish oil.
- Ethyl esters — made by processing fish oil to concentrate EPA and DHA; common in high-potency and prescription products.
- Re-esterified triglycerides (rTG) — ethyl esters converted back into triglycerides.
- Phospholipids — the main form in krill oil.
Phospholipids are also what cell membranes are built from, which is the basis of krill marketing: phospholipid DHA should be "brain-ready." It's an appealing idea. But appealing isn't the same as demonstrated in brain outcomes.
Does phospholipid DHA absorb better?
ODS's summary is careful: some studies suggest that the phospholipid omega-3s in krill oil are somewhat more bioavailable than those in fish oil, while other studies don't.[1] Among fish-oil forms, natural triglycerides, re-esterified triglycerides, and free fatty acids appear somewhat more bioavailable than ethyl esters — but, importantly, "consumption of all forms significantly increases plasma EPA and DHA levels."[1]
Two practical takeaways follow. First, a modest absorption edge doesn't make up for a much smaller dose. Second, no trials we're aware of have shown that krill oil produces better cognitive outcomes than fish oil. The cognitive trials that exist — like the MIDAS trial covered in our DHA and cognitive decline explainer — used algal DHA.
MIXED: Krill oil absorbs better than fish oil — some studies yes, some no (NIH ODS). NO DATA: Krill oil beats fish oil for cognitive outcomes — not shown in head-to-head trials.DHA per capsule: where krill usually loses
Krill softgels tend to be small and lower in EPA+DHA per capsule than concentrated fish oils. ODS doesn't give a typical krill dose, but it notes that a standard 1,000 mg fish oil capsule provides about 180 mg EPA and 120 mg DHA, while concentrated products provide much more.[1] Check the Supplement Facts panel on any krill product: the EPA and DHA numbers are usually a small fraction of the "krill oil" milligrams on the front.
Why that matters for brain-focused buyers: our DHA vs EPA comparison explains why cognitive-aging trials have focused on DHA, at doses in the hundreds of milligrams per day. Reaching that from krill may take several capsules daily.
| Factor | Krill oil | Fish oil (standard / concentrated) |
|---|---|---|
| Main omega-3 form | Phospholipids | Triglycerides, rTG, or ethyl esters |
| Absorption | Some studies show an edge; others don't | All forms raise EPA/DHA; TG and rTG slightly better than ethyl esters |
| DHA per capsule | Usually low — read the label | Standard ~120 mg per 1,000 mg capsule; concentrates much higher |
| Capsule size | Usually small | Varies; concentrates can be large |
| Cost per gram of DHA | Usually higher | Usually lower, especially for concentrates |
| Other compounds | Contains astaxanthin (a pigment) | Varies; some add vitamin E as an antioxidant |
| Allergy note | Crustacean source — shellfish allergy concern | Fish source — fish allergy concern |
| Cognitive trials | Few to none | More, though results are mixed |
How to compare cost the right way
Bottle prices hide the real cost. The useful number is cost per gram of DHA (or EPA+DHA if that's your goal). Here's how to work it out from any listing:
- Find the DHA per serving on the Supplement Facts panel, and the number of capsules per serving.
- Multiply DHA per serving by servings per bottle to get total DHA in the bottle.
- Divide the bottle price by total DHA (in grams).
Run that on a krill product and a concentrated fish oil, and the fish oil usually wins comfortably. That doesn't make krill a bad product — it means you're paying for format, capsule size, and the phospholipid story rather than for more DHA.
Algal oil delivers DHA (and sometimes EPA) without fish or krill. ODS notes algal products typically provide about 100–300 mg DHA per serving and that a small study found algal DHA bioavailability comparable to cooked salmon.[1]
Who should pick which
Choose fish oil (or algal DHA) if your goal is a trial-like DHA dose at the lowest cost per gram, or you want a product in the form used in the major cognitive trials.
Krill oil can make sense if large fish-oil softgels or fishy aftertaste stop you from taking omega-3s consistently, and you're comfortable paying more per gram. Consistency beats theoretical superiority.
Talk to a clinician first if you have a shellfish allergy (krill is a crustacean), take blood thinners — ODS notes high-dose omega-3s can affect bleeding time and package inserts for prescription omega-3s advise INR monitoring with anticoagulants[1] — have surgery coming up, or have atrial fibrillation, since two large trials linked about 4 g/day to a slightly higher atrial fibrillation risk in people with or at high risk of cardiovascular disease.[1]
For where omega-3 fits alongside other foundations, see our anti-aging brain stack and the food-first view in foods that fight brain aging.
What to actually buy
These are the omega-3 products already covered on the site, plus a krill search link if the format suits you. Confirm EPA/DHA per serving on the current listing.
Nordic Naturals Ultimate Omega
Concentrated triglyceride-form fish oil — the omega-3 product we feature most across the site.
Check Amazon price →Nordic Naturals Algae DHA
Algal DHA for people who avoid fish and shellfish — the source type used in the MIDAS cognitive trial.
Check Amazon price →Krill oil softgels
Compare EPA and DHA per serving, not "krill oil mg." Avoid if you have a shellfish allergy.
Check Amazon price →Frequently asked questions
Is krill oil better than fish oil for the brain?
Not based on current evidence. Some studies suggest krill's phospholipid omega-3s are slightly better absorbed, while others don't, and there are no trials showing better cognitive outcomes with krill.
Why is krill oil more expensive?
Krill capsules usually contain less EPA and DHA per capsule, so the cost per gram of DHA tends to be higher than concentrated fish oil.
How much DHA is in krill oil?
It varies by product and is usually much lower than the total krill oil milligrams on the label. Check the EPA and DHA amounts on the Supplement Facts panel.
Can I take krill oil if I'm allergic to shellfish?
Krill are crustaceans, so people with shellfish allergy should avoid krill oil unless an allergist says otherwise. Algal oil is a fish- and shellfish-free alternative.
Do omega-3 supplements interact with blood thinners?
High-dose omega-3s can affect bleeding time. If you take warfarin or another anticoagulant, talk to your clinician; prescription omega-3 labels advise periodic INR monitoring.
Citations
- NIH Office of Dietary Supplements. Omega-3 Fatty Acids — Fact Sheet for Health Professionals. https://ods.od.nih.gov/factsheets/Omega3FattyAcids-HealthProfessional/
- NIH Office of Dietary Supplements. Omega-3 Fatty Acids — Fact Sheet for Consumers. https://ods.od.nih.gov/factsheets/Omega3FattyAcids-Consumer/