How to choose an omega-3 supplement: a plain-English buying guide

The omega-3 aisle is a mess. One bottle costs £4 and one costs £40. One says 1,000 mg, another 500 mg. Some are fish, some are krill, some are algae. One lists EPA and DHA on the front; another buries them in the small print. All claim to be the best.

This is a practical guide to what actually matters on a label and what the brands don't tell you — so you can pay for omega-3 that reaches your bloodstream instead of sitting on a shelf going rancid.

The two molecules that matter: EPA and DHA

Omega-3 is a family of fatty acids. Only two of them do the work people associate with "omega-3" — EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). At EU/UK-authorised doses of 250 mg combined EPA and DHA per day, EPA and DHA contribute to the normal function of the heart, DHA contributes to the maintenance of normal brain function, and DHA contributes to the maintenance of normal vision ^[1].

A third fatty acid — ALA (alpha-linolenic acid), the omega-3 in flax and chia — is technically omega-3 but converts very poorly in the human body to EPA and DHA. A frequently cited stable-isotope study in young women found roughly 21% of dietary ALA converted to EPA and only about 9% to DHA, with conversion to DHA effectively negligible in many men ^[2]. ALA has its own authorised claim, but if your goal is the heart, brain, and vision claims, you want EPA and DHA directly — not ALA and wishful thinking about conversion.

The first thing to check on any omega-3 label is the EPA and DHA content per serving, stated in milligrams. "1,000 mg fish oil" tells you almost nothing — that is the total oil weight, most of which is not EPA or DHA. "450 mg EPA, 300 mg DHA per 2 capsules" tells you exactly what you are buying.

Source: fish, krill, or algae

Omega-3 EPA and DHA come, ultimately, from tiny marine organisms: microalgae. Fish eat the algae (and each other) and concentrate the oils in their tissues. You can enter that chain at any point. Oily fish like salmon, sardines and mackerel are also the NHS-recommended dietary route — current guidance is at least one portion of oily fish per week ^[3].

• Fish oil is the traditional option. Oils from small, short-lived oily fish (sardines, anchovies, mackerel) are generally preferred to oils from larger, longer-lived fish, because heavy metals concentrate up the food chain. Look for a stated species on the label and — ideally — a certification covering heavy-metal and microbial testing.
• Algae oil is the direct vegan option. Commercially produced from strains like Schizochytrium grown in controlled fermentation, algae oil bypasses the food chain entirely. No heavy-metal concentration issue, a lower-impact production footprint, and suitable for vegetarians and vegans. Algae oil can be DHA-dominant or a more balanced EPA/DHA blend depending on the strain — again, check the label.
• Krill oil is a third option — oils from Antarctic krill, with EPA/DHA delivered partly as phospholipids rather than triglycerides. Higher price point, environmental footprint is a topic of active debate, and the research is narrower than for fish or algae oils.

We offer both of the first two: - Our Omega-3 fish oil capsules use oil from small cold-water oily fish, with high EPA and DHA content per serving. - Our Omega-3 algae oil capsules — life'sOMEGA use life'sOMEGA® sustainable algal oil, delivering 600 mg DHA and 200 mg EPA per serving — a clean vegan alternative to fish oil with genuinely comparable EPA and DHA levels.

Chemical form: triglyceride vs ethyl ester

This is where most people lose the plot — and where a lot of cheap supplements save money.

Fish oil comes out of the fish as triglycerides (TG) — three fatty acids on a glycerol backbone, the natural form your body is built to handle. To concentrate EPA and DHA (and strip contaminants), manufacturers often convert the oil to ethyl esters (EE) — cheaper to produce, but absorbed less efficiently by the body. The best oils are then re-esterified back to triglycerides (rTG) — a more expensive step, but delivering a form closer to what your gut recognises. A head-to-head bioavailability study reported relative absorption of about 124% for re-esterified triglyceride versus 73% for ethyl ester (with natural fish triglyceride as the 100% reference) ^[4].

The practical rule: if the label says "triglyceride form" or "rTG", that is a quality signal. If it says "ethyl ester" or EE, you are looking at a lower-absorption, lower-cost product. Most labels don't specify — which is itself a signal; the best brands tell you.

Algae oil is typically supplied in triglyceride form natively.

TOTOX — the freshness number no one talks about

Omega-3 oils oxidise. When they do, the omega-3 degrades into compounds that are both ineffective and potentially irritating to take. The industry standard for measuring oxidation is the TOTOX value — Total Oxidation value — which combines peroxide and anisidine numbers into a single freshness score.

• TOTOX under 10: genuinely fresh, high-quality oil.
• TOTOX 10–26: acceptable under current voluntary GOED standards.
• TOTOX above 26: a rancid supplement that should not be on a shelf.

Very few UK omega-3 brands publish their TOTOX on the box. A brand willing to show you the number — and regular batch testing results — is worth paying more for. A brand that won't? Probably has a reason.

What to check before you buy

A quick checklist you can run down the label in under a minute:

• EPA and DHA in mg per serving, stated clearly. Avoid labels that only list total oil weight.
• Source species named — sardines, anchovies, mackerel, or Schizochytrium algae. "Fish oil" with no species is a red flag.
• Form specified — "triglyceride" or "rTG" preferred over "ethyl ester".
• Antioxidant added — usually natural vitamin E (mixed tocopherols) or rosemary extract — to protect the oil from oxidation in the capsule. Astaxanthin is another good signal.
• Third-party testing — IFOS, GOED, or an independent lab test covering heavy metals (mercury, lead, cadmium, arsenic), PCBs, dioxins, and TOTOX. A certificate of analysis is standard at the quality end of the market.
• Packaging that protects the oil — dark glass or opaque amber bottle, or blister-packed capsules. Never clear plastic.
• A use-by date with decent margin — not a bottle that expires in six months.
• No unnecessary additives — colourings, flavours, allergens. A gel-cap, oil, and an antioxidant are all that is needed.

Common mistakes to avoid

• Buying on milligrams of fish oil rather than EPA+DHA. "2,000 mg!" on the front with 180 mg EPA and 120 mg DHA per capsule is a low-content product in expensive packaging.
• Ignoring the form. Ethyl-ester-only products at budget prices deliver less absorbed EPA and DHA per pound than a slightly dearer rTG oil ^[4].
• Assuming "wild" or "premium" means tested. They are marketing words. Testing certification is the evidence.
• Storing the bottle on a warm windowsill. Heat, light, and oxygen degrade omega-3s. Keep them cool, dark, and sealed.

In practice

A good omega-3 supplement tells you exactly how much EPA and DHA you are getting per serving, from a named source, in a preferred form, tested for purity and freshness, protected from oxidation, and packaged in something that blocks light. Most of the UK market does not meet all of those.

If you want a straightforward fish oil, our Omega-3 fish oil capsules deliver high EPA and DHA per serving from small cold-water oily fish. If you want the same EPA and DHA without the fish, our algae-oil life'sOMEGA gives you 600 mg DHA and 200 mg EPA per serving from sustainable algal fermentation.

Either will cover the 250 mg EPA+DHA daily threshold that sits behind the authorised EU and UK health claims — heart, brain, and vision — without the supplement-aisle gamble.

References

1. European Commission. EU Register of Nutrition and Health Claims Made on Foods. ec.europa.eu
2. Burdge GC, Wootton SA. Conversion of alpha-linolenic acid to eicosapentaenoic, docosapentaenoic and docosahexaenoic acids in young women. Br J Nutr. 2002;88(4):411–420. PubMed: 12323090
3. NHS. Fish and shellfish nutrition. nhs.uk
4. Dyerberg J, Madsen P, Møller JM, Aardestrup I, Schmidt EB. Bioavailability of marine n-3 fatty acid formulations. Prostaglandins Leukot Essent Fatty Acids. 2010;83(3):137–141. PubMed: 20638827

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