Supplements
The front of the bottle says 1000 mg. Turn it over and the supplement facts panel says EPA 180 mg, DHA 120 mg. That is 300 mg of omega-3 in a 1000 mg capsule. The other 700 mg is other fats.
This is not a scam. It is how fish oil works, and it is why comparing products on the front-of-bottle number tells you almost nothing.
Fish oil is a mixture. EPA and DHA are the two omega-3 fatty acids with meaningful evidence behind them, and they make up a fraction of the total oil.
Standard fish oil is typically around 30 percent EPA and DHA combined. A 1000 mg capsule gives you roughly 300 mg. Concentrated fish oil can reach 60 to 85 percent, so a similar sized capsule delivers two to three times more.
Always read the supplement facts panel and add EPA and DHA together. If a product only advertises total fish oil and buries or omits the EPA and DHA breakdown, that is usually because the numbers are unimpressive.
They get quoted as one thing and they are not.
EPA is the one with the stronger evidence for cardiovascular and inflammatory outcomes. Trials looking at triglycerides and at inflammatory markers have generally used EPA-dominant formulations.
DHA is structural. It is concentrated in brain and retinal tissue and is the more relevant one for neurological and eye health, and during pregnancy.
A product that is DHA-dominant is not worse, it is aimed at something different. If your reason for taking it is inflammation or lipids, you want the EPA number to be the larger one.
This is the second variable and it is less well known than the first.
Natural triglyceride (TG). The form omega-3 exists in as it comes from fish. Well absorbed. More expensive to produce.
Ethyl ester (EE). Produced during concentration. Cheaper, and the most common form in retail products. Absorption is measurably lower than the triglyceride forms, and it depends considerably more on taking it with dietary fat.
Re-esterified triglyceride (rTG). Concentrated as an ethyl ester and then converted back into triglyceride form. Combines the higher EPA and DHA content of a concentrate with the better absorption of the natural form. Most expensive to make.
Phospholipid, as in krill oil. Well absorbed, but krill products typically contain far less EPA and DHA per capsule, so the dose becomes the limiting factor.
Most products do not state the form. If the label does not say, it is almost certainly ethyl ester, because that is the cheapest and a manufacturer using rTG has every reason to say so.
Two capsules, both marked 1000 mg.
| Standard EE | Concentrated rTG | |
|---|---|---|
| Total oil | 1000 mg | 1000 mg |
| EPA + DHA | ~300 mg | 800 mg or more |
| Absorption | lower | higher |
To match one concentrated capsule you would need several standard ones, and you would still absorb less of it. A product that hides its form and its breakdown is usually hiding an unimpressive answer to both questions, so the honest ones state EPA and DHA separately and name the form on the label.
Doses vary by what you are trying to affect, and general health intakes are much lower than therapeutic ones.
General intake. Health bodies commonly suggest a few hundred milligrams of combined EPA and DHA daily for cardiovascular health, achievable from two portions of oily fish a week.
Triglyceride lowering. The trials showing meaningful reductions have used substantially higher doses, in the range of two to four grams of combined EPA and DHA daily, and typically under medical supervision.
Inflammation. Studies reporting reductions in C-reactive protein have generally used doses well above general-health intakes.
The gap between a general-health dose and a therapeutic one is large, and it is the reason a single standard capsule often does nothing measurable. CRP is also one of the nine markers in the biological age calculator, which makes it one of the few supplement interventions with a plausible line to a marker in that panel.
Omega-3 fatty acids are highly unsaturated, which is what makes them useful and also what makes them unstable. They oxidise on exposure to heat, light and air. Testing of retail fish oil has repeatedly found products exceeding recommended oxidation limits.
Oxidised fish oil is not merely less effective, and there is reasonable concern that oxidation products are actively undesirable. How to reduce the risk:
The fish burps people complain about are frequently a sign of oxidation rather than an unavoidable feature.
Two portions of oily fish weekly covers general intake for most people. Salmon, mackerel, sardines and Indian mackerel are all good sources, and sardines have the advantage of being cheap.
Plant sources do not substitute directly. Flaxseed, chia and walnuts provide ALA, which the body converts to EPA and DHA at a low and variable rate, generally reported in the single digits as a percentage. Useful, but not a replacement, and vegetarians relying on flax are usually falling short. Algae oil is the vegetarian source that provides EPA and DHA directly.
The Indian diet planner covers fish and other sources across a household-measure database if you want to work out what you are actually getting.
General cardiovascular intake is commonly given as a few hundred milligrams of combined EPA and DHA daily, achievable from two portions of oily fish a week. Trials targeting triglycerides have used substantially higher doses, typically two to four grams, under medical supervision.
Because fish oil is a mixture, and EPA and DHA make up only part of it. Standard fish oil is typically around 30 percent combined EPA and DHA. The 1000 mg refers to total oil, not omega-3 content.
Re-esterified triglyceride. The oil is concentrated as an ethyl ester and then converted back into triglyceride form, which combines a higher EPA and DHA content with better absorption than the ethyl ester form. It is more expensive to produce, which is why most retail products are ethyl ester.
It depends on the goal. EPA has the stronger evidence for cardiovascular and inflammatory outcomes. DHA is structural and more relevant to brain and eye health and to pregnancy. For inflammation or lipids, look for an EPA-dominant product.
Smell it. Fresh fish oil smells mild; a strong fishy or rancid smell indicates oxidation. Keeping it refrigerated after opening, buying it in dark or opaque packaging, and finishing it before expiry all reduce the risk.
Not directly. Flax provides ALA, which the body converts to EPA and DHA at a low and variable rate reported in the single digits as a percentage. Algae oil is the vegetarian source that supplies EPA and DHA directly.
This article is educational and is not medical advice. See the medical disclaimer.
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