Fish oil is the lipid fraction obtained from oily marine fish or marine microalgae and is characterized by a high content of long‑chain omega‑3 polyunsaturated fatty acids (PUFA). Fatty acids in the body function as both energy storage and as building blocks of the cell membrane, deciding what gets through into the cells. The polyunsaturated versions have more double bonds between the carbon atoms, hence more flexibility and more susceptibility to oxidation. Ultimately, long-chain and omega-3 just indicates the length of the carbon backbone and the position of the first double bond. Phew, happy to have this out of the way.

Marine fish (e.g., salmon, mackerel, anchovy, sardines) obtain the omega-3 fatty acids largely through the food chain, ultimately from marine microalgae. The standard process involves fishing, cooking, pressing, and centrifugation to separate oil from water and protein, and different refining steps to remove anything not desired (metals, peroxides, off‑flavors). Ultimately, manufacturers have started producing supplements directly from microalgae (e.g., Schizochytrium, Crypthecodinium), growing and harvesting the biomass, and extracting the oils with organic solvents or with solvent-free methods. Fish and algal-based oils increase the plasma PUFA-levels in a comparable way, with manufacturers often emphasizing sustainable cultivation practices and reduced exposure to heavy metals by using controlled, closed‑system algal production. Obviously, algae products are vegan but considerably more expensive.

The supplements generally come in three forms: triglyceride (TG), re-esterified TG (rTG) and ethyl ester (EE). The key difference between the three forms is what the PUFA-molecules are attached to, i.e., their esterification state. The TG is the native form (with a glycerol backbone) found in in fish tissue and in traditional fish‑oil capsules. The synthetic EE form contains an ethanol group instead of glycerol, created during molecular distillation to concentrate the final product. The rTG form starts as EE but then hydrolyzed back to free fatty acids and re‑attached to glycerol. This is a controversial topic but in comparative trials, rTG tends to yield slightly higher rises in plasma PUFA-levels than natural TG at the same mg dose, while TG is more bioavailable than EE forms. The absorption of EE, however, can be markedly improved when taken with a lipid‑rich meal, whereas TG‑based forms are less dependent on meal fat content.

The two main long-chained omega-3 PUFAs are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). They can be synthetized from alpha-linoleic acid (ALA) with a ca. 1-10% efficiency in humans but direct intake is much more efficient. EPA is a signaling and regulatory molecule, lowering plasma triglycides, while DHA is part of the neuronal and retinal membrane structure, critical for brain development and synaptic plasticity. Docosapentaenoic acid (DPA) is a lesser known omega-3 PUFA with emerging roles in cardiovascular protection, inflammation resolution, and neural function. It may serve as a metabolic reservoir for EPA and DHA, though clinical evidence in humans is still evolving.

Many randomized trials evaluating cardiovascular prevention have used approximately 1 g of EPA+DHA per day, although official dietary guidelines for the general population typically recommend only 250–500 mg EPA+DHA per day from diet alone. If you start supplementing omega-3, ask your doctor first.

The price per gram of EPA+DHA is calculated as follows:

This metric normalises the price you pay across products regardless of serving size, softgel count or total fish oil content. A product with 1000mg of fish oil per softgel and 300mg of EPA+DHA is not comparable to one with 500mg of fish oil and 400mg of EPA+DHA — the raw price per softgel tells you nothing useful.

Most fish oil products display total fish oil or total omega-3 content prominently, while EPA and DHA are listed as a sub-item in smaller print. Also, serving size can be different (often 2-4 softgels needed) to reach the declared quantity on the label.

The database will grow soon with products available in Europe as well.