EPA (C20:5 n-3)

EPA, eicosapentaenoic acid, is one of the two long-chain omega-3 fats measured on this panel. Where DHA is mostly structural and concentrates in brain and retinal tissue, EPA is mostly signalling. It is the substrate for the resolvins and other mediators that bring an inflammatory response to a close.

Serum EPA reflects intake over recent weeks, which makes it a faster-moving marker than the Omega-3 Index. The index measures red cell membranes and lags by months, so the two answer different questions: EPA here tells you about current intake, the index tells you about the accumulated position.

Below 3 umol/L indicates low circulating EPA. Because EPA competes with arachidonic acid for the same enzymes, a low result shifts the balance of signalling molecules toward the inflammatory side.

The usual cause is a diet built around processed food and industrial seed oils, with little oily fish. Linoleic acid from those oils competes for the same desaturase enzymes that would otherwise produce EPA from plant precursors.

EPA-dominant supplementation raises this marker faster than a general fish oil, because most standard fish oils are formulated closer to a 1:1 or DHA-dominant ratio.

Between 3 and 20 umol/L your circulating EPA sits inside the reference range for this panel.

Read this alongside your Omega-3 Index. A good EPA result with a low index usually means intake has improved recently but has not yet worked through into membranes, which takes about three months.

Above 20 umol/L generally reflects high-dose supplementation rather than diet.

The consideration at high intakes is bleeding time, which matters if you take anticoagulant or antiplatelet medication. Digestive effects are also common at higher doses.

Review your total omega-3 intake across supplements, cod liver oil and fortified foods, and raise a high result with your practitioner if you take medication affecting clotting.

Processed-food dietary patterns leave EPA low while supplying large amounts of the omega-6 fats it competes with. The effect is not simply a shortage of EPA but a shift in the ratio that determines which signalling molecules get made.

This is the marker where the Western dietary pattern shows up most directly as inflammatory tone rather than as a nutrient shortfall in the older sense.

Salmon, mackerel, sardines, herring and anchovies several times a week are the direct sources.

Removing industrial seed oils, refined sugars and processed foods reduces the competition for the enzymes that produce EPA.

Walnuts and chia supply ALA, the plant precursor. Conversion to EPA is real but inefficient, so treat them as a supporting source rather than a substitute for marine sources.

EPA-dominant fish oil supplying 1 to 2 g EPA daily. Look for a 2:1 or 3:1 EPA to DHA ratio rather than a general formulation.

Standalone EPA is available where mood or inflammatory tone is the reason for taking it.

Algae-based EPA capsules cover plant-based diets. Take any of these with a fat-containing meal, since absorption drops considerably without one.