A bloke came into the shop recently holding a supermarket fish oil he had bought for a few quid, wanting to know if it was any good. I turned the tub round, read the back, and showed him the problem: to get the amount of actual omega-3 used in most of the research, he would need to swallow six of those capsules a day. That is the fish oil supplement industry in one label. It is one of the most worthwhile supplements you can take and one of the easiest to buy badly. This guide covers everything I explain across the counter: what omega-3 does, EPA versus DHA, the forms nobody tells you about, dosing, and how to spot a tub worth your money.
- Worth knowing Every fish oil label lists these two, and the ratio matters more than the marketing.
- This is the difference between a good fish oil supplement and a cheap one, and almost nobody talks about it.
Why bother with omega-3 at all?
EPA and DHA are the two long-chain omega-3 fatty acids your body struggles to make in meaningful amounts, so they have to come from diet, and in practice that means oily fish. The official UK advice is at least one portion of oily fish a week. Most people I serve do not manage one portion a month.
The established science is worth stating plainly. EPA and DHA contribute to the normal function of the heart. DHA contributes to the maintenance of normal brain function and normal vision. At higher intakes, DHA and EPA contribute to the maintenance of normal blood triglyceride levels and normal blood pressure. These are the authorised claims, and behind them sits one of the largest research bases in nutrition. Omega-3 is also of real interest for joint comfort and general inflammatory balance, where the research is promising if less settled. If you rarely eat oily fish, a decent omega-3 supplement is one of the few I would call close to essential.
EPA vs DHA: what is the difference?
Every fish oil label lists these two, and the ratio matters more than the marketing. As a rule of thumb, EPA is the one most studied around inflammatory balance and mood, while DHA is the structural one, a major building block of the brain and the retina. For general health you want a sensible amount of both. If joint comfort or mood support is your focus, look for a product weighted towards EPA. If you are pregnant (speak to your GP or midwife first) or focused on brain and eye health, DHA becomes more important.
Here is the trick the cheap end of the market plays: the front of the tub shouts "1000mg Fish Oil" but the back reveals only 300mg of that is actually EPA and DHA combined. You are buying the total oil, but the benefit lives in the EPA and DHA numbers. Always read the back, never the front.
Triglyceride vs ethyl ester: the form nobody mentions
This is the difference between a good fish oil supplement and a cheap one, and almost nobody talks about it. Omega-3 in fish exists naturally in triglyceride form. To concentrate the oil, manufacturers convert it to ethyl ester form. Better products then convert it back, at extra cost, to what is called re-esterified triglyceride. Why care? Absorption. Research comparing the forms shows triglyceride-form omega-3 is absorbed meaningfully better than ethyl ester, and it also tends to be more stable against oxidation. Cheap high-street fish oil is almost always ethyl ester, because it is cheaper to make. The label will rarely say, but a brand that has paid for triglyceride form usually shouts about it, and that is one reason we stock Wiley's Finest fish oils, which are built on exactly this kind of quality-first approach.
Then there is the third form: phospholipid, which is how omega-3 comes packaged in krill oil. Phospholipids are the same form your cell membranes use, and studies comparing krill with standard fish oil at matched doses show strong absorption, plus krill naturally contains astaxanthin, an antioxidant that protects the oil from oxidising. Our LSC Krill Oil 500mg is the one I point people to if regular fish oil repeats on them, though anyone with a shellfish allergy should avoid krill entirely.
View in the shop
How much should you take?
For general maintenance, I suggest aiming for around 500mg of combined EPA and DHA per day, which roughly matches eating oily fish twice a week. The authorised heart function claim is based on 250mg of EPA and DHA daily, so treat that as the floor. For targeted support, joints or triglycerides for instance, research typically uses 1000 to 2000mg of combined EPA and DHA daily. Above that, or if you take blood-thinning medication, talk to your GP or pharmacist first. And take it with a meal containing fat; absorption is noticeably better than on an empty stomach.
Freshness, purity and the rancid oil problem
Fish oil goes off. Oxidised omega-3 not only smells foul, it loses the properties you paid for. A quality product will be protected with antioxidants, sold in dark or opaque packaging, and fresh enough that if you bite a capsule it tastes of not much at all. If your fish oil gives you genuinely foul, rancid burps, that is a quality signal, and the answer is not to endure it but to buy better oil. Look too for purification standards: heavy metals and PCBs concentrate up the food chain, so oils from small fish like anchovies and sardines, or from krill, start cleaner, and reputable brands publish their testing.
What about vegans?
Fish do not make omega-3, the algae they eat do. Algae oil supplies EPA and DHA directly, no fish involved, and it is the right answer for vegans and vegetarians rather than flaxseed oil, which contains a shorter omega-3 (ALA) that the body converts to EPA and DHA very inefficiently. You will find our full range, fish, krill and plant options together, in the Omega Oils collection.
Frequently asked questions
What should I look for on a fish oil label?
Ignore the total oil figure and find the combined EPA and DHA per serving; aim for at least 500mg. Then look for the form (triglyceride or phospholipid beats ethyl ester), a named small-fish or krill source, and evidence of purity testing.
Is krill oil better than fish oil?
Different, and for some people better. Krill delivers omega-3 in phospholipid form with natural astaxanthin, and it is gentler on those who get fishy repeats. Concentrated triglyceride fish oil delivers more EPA and DHA per capsule for the money. Both are legitimate choices; avoid krill if you have a shellfish allergy.
When is the best time to take omega-3?
With your largest meal of the day, because dietary fat improves absorption. Beyond that, consistency beats timing.
Can I take too much?
Very high intakes can affect blood clotting, so if you are on anticoagulants or heading for surgery, involve your GP. For most healthy adults, up to 2000mg of combined EPA and DHA daily is a well-studied range.
From the shop
Most supplements aren't worth the tub they come in, and bargain-bin fish oil is my go-to example: ethyl ester form, feeble EPA and DHA per capsule, and half-oxidised by the time you finish the bottle. Buy once, buy properly. Check the back label, count the EPA and DHA, and if you want a second opinion, bring the tub into the shop on Hyde Road and I will read it with you. I have been turning tubs round for thirty years and it still tells you everything.