What to check before buying
Three things, in order, and the first one is not close.
EPA + DHA per serving, not fish oil weight. This is the single most
misleading label practice in the supplement aisle, and it is entirely legal. A
bottle shouting “1,000 mg Fish Oil” on the front typically contains 180 mg EPA
and 120 mg DHA — 300 mg of the fatty acids that do the work, and 700 mg of
other fats along for the ride. The front of the bottle is describing the
weight of the oil, not the dose of the nutrient. Turn it over, find the two
lines that say EPA and DHA, and add them. Then check the serving size, because
the panel may be describing two or three softgels rather than one. Do this
arithmetic and the price ranking of an entire shelf usually inverts: the
“1,200 mg” bargain bottle can cost more per gram of EPA+DHA than the
concentrate next to it.
Form: triglyceride versus ethyl ester. Natural fish oil is a triglyceride.
To concentrate it, manufacturers convert it to ethyl ester, and the cheaper
products stop there; more expensive products convert it back, which is what
“re-esterified triglyceride” or “rTG” means on a label. Research suggests rTG
absorbs somewhat better, particularly on an empty stomach, and is a little
more resistant to oxidation. It is a genuine but modest advantage, and it
usually costs double. Ethyl ester taken with a fatty meal is a perfectly
reasonable choice; ethyl ester taken with black coffee is a worse one.
Freshness. Omega-3s are highly unsaturated, which is exactly why they
oxidise. Independent surveys have repeatedly found retail fish oil exceeding
recommended peroxide and anisidine limits, sometimes badly, and oxidised oil is
both unpleasant and plausibly counterproductive. Look for IFOS certification or
an equivalent program publishing TOTOX values by lot. Then apply the check
nobody can take from you: bite a softgel. Fresh fish oil tastes of fish. Rancid
fish oil tastes sharp, painty, and obviously wrong. Heavy citrus flavouring
exists partly to make that test impossible, which is worth knowing before you
buy the lemon version.
How we evaluated
We compared widely available omega-3 products on cost per gram of EPA+DHA,
form, published third-party testing for oxidation and contaminants, capsule
burden at a useful daily dose, and label honesty — specifically whether the
front of the package describes the nutrient or the oil. We read user reports
for the practical failures: fishy repeat, leaking softgels, bottles arriving
warm.
We have not lab-tested these products. We did not measure peroxide values,
we did not assay EPA and DHA content, and we did not send anything to a
laboratory. Everything here is based on published certifications, supplement
facts panels, manufacturer disclosures, and existing independent testing
programs. Where a freshness claim comes from the manufacturer rather than an
outside certifier, we have said so in the cons.
Ratings follow the methodology on our How We Test Products page. Some links
earn us commission. Commissions never affect ranking or inclusion — our
value pick pays us a fraction of what the premium pick does, and it is still
the value pick.
What the evidence supports — and where it stops
Start with what is solid. High-dose omega-3s have been shown to lower
triglycerides, substantially and reliably, at doses of roughly 2–4 g of
EPA+DHA daily. That is a prescription-territory dose and a genuine
pharmacological effect, not a wellness claim.
Now the part the category does not advertise. Three large, well-run randomised
trials of roughly 1 g daily in general and higher-risk populations did not find
a reduction in cardiovascular events. A separate trial of a high-dose purified
EPA drug did report benefit, but it used four grams of a prescription product
and its comparison oil has been argued over ever since. Taking a gram of
supermarket fish oil and expecting the result of that trial is not a
conclusion the evidence supports.
Elsewhere the picture is mixed and honest about it. Research suggests omega-3s
may help with morning stiffness and tender joint counts in rheumatoid
arthritis, with effects modest enough that they supplement rather than replace
treatment. A large trial of omega-3 for dry eye disease found no benefit over
placebo. Cognitive protection in healthy older adults has not been
demonstrated. And there is a finding worth stating plainly because supplement
pages rarely do: several high-dose trials reported an increased incidence of
atrial fibrillation. That is a reason to be cautious about pushing the dose up
on your own initiative.
The defensible summary is that omega-3s are a food-first nutrient with one
proven high-dose use and a lot of hypotheses that did not survive testing. The
full grading is in the evidence review linked below.
FAQ
Do I still need this if I eat salmon twice a week? No. Two servings of
oily fish per week puts you in the intake range the entire observational case
is built on. Supplements exist for people who will not or cannot eat fish, not
as an upgrade for people who already do.
Should I refrigerate it? Yes, once opened. Cold slows oxidation, and for
fish oil that is the main thing shortening its useful life. Freezing softgels
also reduces fishy repeat, because they pass the stomach before dissolving.
What about krill oil or cod liver oil? Krill oil is marketed on
phospholipid absorption but delivers far less EPA+DHA per capsule at a much
higher price, so the arithmetic rarely works. Cod liver oil is a real food-form
option but carries preformed vitamin A, which accumulates — check the amount
and count it against everything else you take.