Benefits · Heart
Heart & circulation
This is the most heavily studied thing omega-3 does, and also the area where the headlines have been most confusing. Large trials have come to different conclusions, and the reasons they differ are worth understanding before you decide whether a supplement is for you.
Triglycerides
Well established
Of everything attributed to omega-3, the effect on blood triglycerides is the least controversial. EPA and DHA reduce the amount of triglyceride the liver packages up and releases, and they speed the clearance of triglyceride-rich particles from the blood. The effect is dose-dependent and consistent enough that prescription-strength omega-3 is an approved medicine for very high triglycerides in several countries.
Two caveats worth stating. First, prescription doses are far higher than any supplement — typically around 4 g of EPA and DHA daily, against the 250 mg in a Krillzyme softgel. Second, the effect is proportionally larger in people who start with high triglycerides than in people whose levels are already normal. A supplement is a contribution to overall omega-3 intake, not a substitute for a prescription where one is warranted.
The omega-3 index
Reasonably supported
The omega-3 index measures EPA and DHA as a percentage of the fatty acids in your red blood cell membranes. It’s a better picture of long-term status than a plasma reading, because membranes change slowly — it reflects months of intake rather than what you ate yesterday.
Population research has repeatedly found that people with a higher omega-3 index tend to have better cardiovascular outcomes than people with a low one. That’s an association rather than proof of cause, and people who eat a lot of oily fish differ from people who don’t in plenty of other ways. But it is a consistent association, and it is the clearest reason to care about your intake at all.
Blood pressure
Reasonably supported
Meta-analyses of controlled trials find omega-3 produces a small but real reduction in blood pressure, on the order of a couple of millimetres of mercury on average, with larger effects in people who are hypertensive to begin with. That is a modest effect for an individual and a meaningful one across a population. It is not a replacement for antihypertensive medication, and nobody should stop taking one on the strength of it.
Why the big trials disagreed
Early or mixed
Several large randomised trials have tested omega-3 supplementation against cardiovascular events, and they did not all agree. Some found no benefit over placebo. At least one found a substantial reduction in events using a high-dose purified EPA preparation. Another using a different high-dose formulation found nothing.
The plausible explanations are unglamorous but important: the trials used very different doses, different ratios of EPA to DHA, different comparison oils, and enrolled populations with very different baseline omega-3 status and background medication. A trial in people already well-supplied with omega-3, all taking statins, has much less room to show an effect than one in a deficient population.
The honest summary: omega-3 reliably changes several measurable things about your blood, and whether that translates into fewer events for any given person is still genuinely contested. Anyone who tells you the question is settled — in either direction — is overstating it.
Where krill oil fits
Krill oil delivers the same two fatty acids as fish oil, attached to phospholipids rather than triglycerides. Studies of that form have generally found it raises the omega-3 index at least as efficiently per gram of EPA and DHA. The absorption research is covered here, including the trials that found no difference between the two forms.
What krill oil does not do is change the dose question. If your doctor has told you to take gram-level omega-3 for a specific reason, a once-daily supplement is not that.