Fish Oil: The Number on the Front Isn't the Dose

Fish oil is the supplement most likely to be sold on a number that doesn't mean what buyers think it means. A bottle advertising 1,000 mg of fish oil is telling you the weight of the oil, not the amount of the compounds anyone actually takes fish oil for — and the gap between those two figures is frequently large enough to change which product is the better buy.

01Fish oil is the carrier, EPA and DHA are the point

The omega-3 fatty acids of interest are EPA and DHA. Fish oil is simply the material they arrive in, and its total weight includes a great deal that isn't either of them.

A typical inexpensive fish oil might be around 30% EPA and DHA combined, meaning a 1,000 mg softgel delivers roughly 300 mg of what you came for. A concentrated product might be 60% or higher, delivering double from the same capsule size. Both labels can honestly print 1,000 mg on the front.

So the only comparison worth making is the combined EPA and DHA figure per serving, and how many softgels that serving requires. A brand that leads with total fish oil rather than EPA and DHA is drawing your eye to the flattering number.

02EPA and DHA are not interchangeable

Worth knowing, because ratios differ substantially between products.

DHA is a major structural component of cell membranes, notably in the brain and the retina, which is why it features prominently in prenatal and infant nutrition. EPA is more associated with the signalling side of omega-3 activity.

Neither is superior in general — they do different things, and a product's ratio should follow what you're interested in rather than being ignored. Most general products contain both, and the balance varies more than the marketing suggests.

03Triglyceride, ethyl ester, and why it matters

This is the form question, and it's the one most fish oil buyers have never heard of.

Omega-3s in fish are in triglyceride form. To concentrate them, manufacturers typically convert the oil to ethyl esters — a processing step that makes concentration possible. Some products stop there. Others convert back to a triglyceride form afterwards, which costs more.

Research comparing them has generally found the re-esterified triglyceride form is better absorbed than the ethyl ester form. It also tends to be more stable against oxidation. Ethyl ester products aren't useless — plenty of research used them — but a label specifying triglyceride form is telling you the manufacturer paid for a step that improves what you actually absorb.

If a label says nothing about the form, it's usually ethyl ester.

04Rancidity: the problem you can smell

Omega-3s are polyunsaturated, which is exactly what makes them biologically interesting and chemically fragile. They oxidise — with heat, light, oxygen and time — and oxidised fish oil is not merely less effective. Testing of retail fish oil has repeatedly found products exceeding recommended oxidation limits, sometimes a substantial share of those sampled.

This is the single biggest quality issue in the category and almost nothing on a label addresses it.

Two markers exist for it: peroxide value and anisidine value, measuring early and later oxidation respectively, often combined into a TOTOX figure. A brand publishing these numbers for the batch you're holding is doing something meaningful. A brand that doesn't is asking you to assume.

The practical test: fishy burps are frequently blamed on fish oil generally, but strong fishy taste or smell is often a sign of oxidation rather than an inevitable feature. Fresh, well-made fish oil is comparatively mild.

05Heavy metals, and why testing isn't optional here

Fish accumulate contaminants, and larger, longer-lived fish accumulate more. Well-made fish oil is molecularly distilled to remove them, and third-party testing is what confirms it worked.

This is a category where an unpublished certificate should genuinely give you pause — not as a general principle, but because the raw material carries a specific, well-documented contamination risk that processing is supposed to solve.

06Practical points

Take it with a meal containing fat, since omega-3s are fat-soluble and absorb considerably better with food. This also reduces the reflux and aftertaste people complain about.

Store it cool and dark, and if a bottle smells strongly rancid, don't finish it out of thrift.

And if you take blood-thinning medication, omega-3s at higher doses are a conversation to have with your doctor rather than a decision to make alone.

07How to read the label

Find combined EPA and DHA per serving, not total fish oil. Check how many softgels make that serving. Look for triglyceride form. Look for published oxidation values and heavy metals testing tied to your lot. And note the source — smaller fish like anchovy and sardine carry less contamination burden to begin with.

08How we approach it

Our approach is to lead with EPA and DHA amounts rather than total oil weight, to state the form, and to publish an independent certificate for every lot covering identity, potency, heavy metals and microbials.

Fish oil rewards a specific kind of scepticism. The number on the front is the least useful figure on the bottle, the form is rarely stated, and the freshness problem is the one thing that most determines whether you're taking something worthwhile — and it's the one thing the category is quietest about.

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.