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There is no single optimal ratio — there are amounts per purpose, and they stand as milligrams of EPA and DHA on the back of the pack.
Also known as: EPA and DHA · which one for what · what the back of the pack says
Open in the tool — with search and all the links →This compilation is for information and replaces neither medical diagnosis nor treatment. If you have symptoms, see a doctor.
The honest answer first: there is no single optimal ratio. Anyone looking for one is looking for a number the studies never delivered — they did not compare ratios, they examined amounts for particular purposes. What is usable is therefore not “1 to 2” or “2 to 1”, but: how much EPA and how much DHA stood in the study that matches your own question.
EPA and DHA are two different fatty acids, not two names for one thing. DHA is building material: it sits in the membranes of brain and retina, and in the membranes of the visual cells it makes up a very high share of all fatty acids. EPA is more raw material: from it the body makes the messengers that bring an inflammation back down, in direct competition with arachidonic acid. The body can barely convert one into the other: in adults EPA yields very little DHA, and conversely a small part of DHA is converted back into EPA. What you take is therefore largely what you get.
What the studies used — sorted by purpose:
· Basic supply. The European authority names 250 mg EPA and DHA a day for adults and says nothing about the ratio. What usually lands on the plate — two portions of oily fish a week — lies roughly between 1 to 1 and 1.5 to 1 in favour of EPA.
· Pregnancy and breastfeeding. Here it tips clearly towards DHA: recommended are the 250 mg EPA and DHA plus a further 100 to 200 mg DHA a day. That is the one place where one side of the ratio is named outright.
· Triglycerides in the blood. Needed are 2 to 4 g EPA and DHA a day; they then fall by 20 to 30 per cent, within four to eight weeks. Both work. In direct comparison DHA lowers triglycerides somewhat more — and raises LDL somewhat more at the same time; EPA does both less markedly. A prescription preparation works with pure EPA, 4 g a day; the large trial on it is still discussed today, because the placebo used may not itself have been neutral.
· Joints and inflammation. Studied were 2 to 3 g EPA and DHA a day over at least three months. The preparations used were mostly EPA-weighted — but what was tested was the amount, not the ratio.
· Mood. In the summaries of the studies a signal appeared where EPA made up at least 60 per cent of EPA plus DHA, at about 1 g EPA a day; DHA-weighted preparations did not show it. That is an observation on the existing pool of studies, not a recommendation — and those studies are small and inconsistent.
· Dry eyes. The results contradict each other; no ratio came out of them.
What is on the packs. Standard fish oil is called “18/12”: 18 per cent EPA and 12 per cent DHA — that is 180 mg EPA and 120 mg DHA per 1000 mg, so 1.5 to 1. That is the ratio most people take without knowing it. Concentrates shift it in both directions. Algae oil is mostly DHA-weighted, some kinds carry DHA only, newer ones EPA alongside. Krill oil sits roughly like fish oil, but with far fewer milligrams per capsule. Cod liver oil is roughly 1 to 1.2, so slightly in favour of DHA. Linseed oil does not belong in this row: it delivers ALA, of which 5 to 10 per cent becomes EPA but under 1 per cent DHA — it therefore shifts the ratio towards EPA, at very small absolute amounts.
What the omega-3 index says about it: nothing. It measures the share of EPA and DHA together among the fatty acids of the red blood cells; above 8 per cent counts as desirable. The ratio between the two is not in it. And it needs time: because red blood cells live about 120 days, it only moves over three to four months of steady intake.
Not to be confused: the other ratio. Omega-6 to omega-3 is quite a different number. For western diets 15 to 1 up to 20 to 1 are quoted, and many hold 4 to 1 or lower to be favourable — these figures are disputed, because they come from observation and because omega-6 is not harmful in itself. Shifting that ratio works better with more omega-3 than with less omega-6.
The usable rule is therefore not “take this ratio”, but: read on the back milligrams of EPA and milligrams of DHA — not the capsule weight — and choose by the purpose, not by a ratio number.
Some kinds carry DHA only, newer ones EPA alongside. The source from which the fish themselves get their omega-3.
The ratio is similar, the absolute amount is not: 60 to 150 mg EPA and DHA per 1000 mg capsule against about 300 mg for fish oil.
Slightly in favour of DHA, plus vitamins A and D. Here vitamin A is the amount that decides, not the ratio.
The conversion is 5 to 10 per cent for EPA and under 1 per cent for DHA. A tablespoon of about 10 g delivers 5 to 6 g ALA.
Without fat less is taken up — true for every one of these oils, and the simplest adjustment there is.
All these oils oxidise. Rancid oil smells and tastes of it — the one point anyone can check without a laboratory.
Measurable, and reached with the amounts from the triglyceride studies. Alongside a blood thinner that is a second amount on the same route — the calculator shows it.
The studies examined amounts for purposes; they did not compare ratios. Looking for a ratio number is looking for an answer that does not exist in that form.
DHA sits in the membranes of brain and retina. From EPA the body makes the messengers that bring an inflammation back down. That is why the question arises at all.
In adults EPA yields very little DHA; from DHA a small part of EPA is converted back. What you take is largely what you get.
180 mg EPA and 120 mg DHA per 1000 mg of oil. That is the ratio most people take without knowing it.
250 mg EPA and DHA plus a further 100 to 200 mg DHA a day. That is the only place where the recommendation names one of the two on its own.
It counts EPA and DHA together. And it needs three to four months, because red blood cells live about 120 days.
It delivers ALA. Of that 5 to 10 per cent becomes EPA but under 1 per cent DHA — somewhat more in women than in men.
The quoted 15 to 1 against 4 to 1 are disputed and come from observation. The ratio is shifted more easily by more omega-3 than by less omega-6.
Share of EPA and DHA together among the fatty acids of the red blood cells; above 8 per cent counts as desirable. It says nothing about the ratio and only moves over three to four months.
The one point where the amount clearly acts measurably: 2 to 4 g EPA and DHA a day lower them by 20 to 30 per cent, within four to eight weeks.
Belongs to the comparison of the two: DHA raises LDL somewhat more than EPA, while lowering triglycerides somewhat more.
The nutrient behind it — a guide value of 250 mg EPA and DHA a day, with no ratio given.
That is the order of magnitude the 250 mg a day comes from — salmon, herring, mackerel, sardine. The ratio there lies roughly between 1 to 1 and 1.5 to 1.