What Are the Signs You Need Omega-3? What Low Intake Looks Like

There is no reliable sign that you need omega-3. Low intake of EPA and DHA produces no symptom you can feel, the NHS has no test for it, and the online checklists (dry skin, brittle nails, poor concentration, aching joints, low mood, dry eyes) list things that have commoner causes. The one objective measure is the omega-3 index, the share of EPA and DHA in your red blood cells. The everyday guide: do you eat oily fish? Most UK adults eat less than the one portion a week the NHS advises, and people who eat no fish, vegans in particular, sit lowest.^{1, 2, 3} Look at your plate, not your fingernails.

• Symptoms: none is specific to omega-3; each has a commoner cause and a proper test
• The measure: the omega-3 index, on which the UK sits in the lowest band
• Likely to be low: no oily fish, vegan or vegetarian, pregnant or breastfeeding
• The fix: two portions of fish a week, one oily, or an algal DHA source, read in milligrams

What are the signs you need omega-3?

None of the six "signs" online has been validated as a marker of omega-3 status; each is common for other reasons.

What are the symptoms of omega-3 deficiency?

True essential fatty acid deficiency is rare and looks nothing like the lists: a scaly rash, poor wound healing and slow growth in infants, seen almost only in people fed intravenously for weeks without fat.⁴ Nobody on a mixed diet, vegan included, develops it: ALA, the strictly essential omega-3, is in flaxseed, chia, walnuts and rapeseed oil. A fish-free diet produces low status instead: EPA and DHA that were "low but stable" in 659 British men, lower in vegetarians and vegans than in meat-eaters and no lower after twenty years on the diet than after one.³

How do you know if you are lacking omega-3?

Ask what you eat. SACN's population figure is about 450 mg of EPA and DHA a day, which two portions of fish a week, one oily, supply; without oily fish the rest of the diet gives a few tens of milligrams.⁵ If you cannot remember your last sardine, mackerel, salmon, trout or kipper, your intake is below the UK guideline, and so is most of the country's: the National Diet and Nutrition Survey finds average oily fish consumption below one 140 g portion a week in every age group.²

Can I test my omega-3 levels at home? (the omega-3 index)

Yes, privately, by finger-prick. The omega-3 index is the percentage of red blood cell fatty acids that is EPA plus DHA. Its proposers tied 8% or more to the lowest risk of coronary death and 4% or below to the highest, and a 2016 survey of 298 studies placed the UK, with most of Europe and North America, in that lowest band.^{6, 1} These are associations. The large trials dosed by the milligram, not to an index target, so none has shown that lifting someone from 4% to 8% changes outcomes. And the NHS does not offer the test, so you interpret it yourself: it reports your intake over the past three to four months, and a low result in a non-fish-eater is expected, not alarming.

Who is most likely to be low?

• Anyone who eats no oily fish. The gap between a few tens of milligrams and the 250 mg of EPA and DHA behind the register's heart wording is the whole story.^{5, 7}
• Vegans and vegetarians. In 165 long-term vegans the mean index was 3.7%; 254 mg a day of algal EPA and DHA for four months raised it from 3.1% to 4.8% in those below 4%.⁸ ALA alone does not close the gap: about 5% becomes EPA and under 0.5% DHA.⁹ Does flaxseed oil contain omega-3, 6 and 9 has the detail.
• Pregnancy and breastfeeding. The baby draws DHA from the mother, so the register sets 200 mg a day of DHA on top of the adult 250 mg.⁷ In a large trial, omega-3 in pregnancy reduced early preterm birth only in women who started with low omega-3 status, from 3.2% to 0.7%.¹⁰

Do the symptoms people search for respond to omega-3?

Mostly not: a symptom that does not improve when omega-3 goes up was never a sign that it was down.

• Dry eyes. 3 g of EPA and DHA a day for a year was no better than olive oil on symptoms or signs in 535 people.¹¹
• Low mood. In diagnosed depression, omega-3 added to usual care gave a small-to-moderate benefit in the Cochrane pooling, about 2.5 points where 3 is the smallest change patients notice, at very low certainty; in 18,353 adults without depression, 1 g of fish oil a day for five years did not lower the number of new cases.^{12, 13}
• Joints. In rheumatoid arthritis, 2.7 g or more a day for three months reduced painkiller use: a prescription-level amount, not a label dose; for osteoarthritis, what is the best joint supplement sets out the evidence.¹⁴
• Skin. Dry skin has not been tested in a controlled trial, and the Cochrane review of eczema found no convincing evidence for any supplement.¹⁵
• Concentration. Across 38 trials and 49,757 adults, omega-3 did not change cognitive scores.¹⁶ Is omega-3 good for your brain has the detail.

What depletes omega-3 in the body?

Status follows intake. Red blood cells live about four months, so the index is a rolling average of what you ate: it falls when fish or supplements stop and rises when they restart. A high linoleic acid (omega-6) intake competes with ALA for the same enzymes; in the British vegetarian men plasma DHA was lower the higher their linoleic acid.³ Alcohol, stress, caffeine and "toxins" do not appear in the evidence.

How long does it take to correct a low omega-3 level?

Plasma responds within two weeks; red cells take months. 600 mg of DHA a day from algal-oil capsules or cooked salmon raised plasma DHA by about 80% in a fortnight; the vegan trial took four months.^{17, 8} There is no symptom timeline, because there is no symptom; should omega-3 be taken daily explains why the trials dosed daily for years.

How to raise your omega-3 intake

Fish first: at least two portions a week, one oily.¹ If fish is off the menu, algal oil is the direct route to DHA, the molecule fish get from algae, and the yardsticks on any label are the register's: 250 mg of EPA and DHA (heart), 250 mg of DHA (brain and vision), 200 mg more DHA in pregnancy.^{7, 17} Algae omega-3 vs fish oil compares the sources. Wellgard Vegan Omega 3 Gummies supply 50 mg of algal DHA and 50 mg of ALA per two gummies, against the 250 mg of DHA at which the brain and vision wording applies, with vitamin D3 at 100% of the NRV, which contributes to the maintenance of normal bones and teeth, and vitamins A, C and E: a chewable source of preformed DHA for a fish-free household. For ALA, two tablespoons of ground flaxseed or 25 g of chia or walnuts reach the 2 g a day behind the register's cholesterol wording; Wellgard Vegan Omega 3 6 9 is a flaxseed-oil capsule supplying 692 mg of ALA per two capsules against that 2 g, with 152 mg each of linoleic and oleic acid and 10 mg of vitamin E, which contributes to the protection of cells from oxidative stress, and no EPA or DHA, so it is the plant ALA source alongside fish or algal oil. How much omega 3-6-9 do I need daily has the label-reading table; the Wellgard omega-3 guide the full picture. How to get enough omega-3 on a vegan diet covers the plant route, and why fish oil is no longer recommended the dose question.

Frequently asked questions

Does the NHS recommend omega-3 supplements?

Not for the general population: the advice is food, two portions of fish a week including one oily.¹ It does say to avoid fish liver oil supplements in pregnancy, because of their vitamin A.

What vitamin are you lacking if you have dry eyes?

Usually none. Dry eye is mostly tear evaporation; the NHS approach is lid care and drops, and omega-3 at 3 g a day was no better than placebo in the largest trial.¹¹

How can you tell if you're low on omega-3 without a test?

By intake: no oily fish most weeks, or a vegan or vegetarian diet without an algal source, meant low EPA and DHA status in every study that measured it.^{3, 8} Is there any danger when taking omega-3 covers the opposite question.

Sources

1. NHS. Fish and shellfish. nhs.uk.
2. Public Health England. NDNS: results from years 9 to 11. gov.uk.
3. Rosell MS. Long-chain n-3 fatty acids in plasma in British meat-eating, vegetarian and vegan men. 2005. PubMed 16087975.
4. Gramlich L. Essential fatty acid deficiency in 2015. 2015. PubMed 26187936.
5. SACN. Advice on fish consumption: benefits and risks, 2004. gov.uk.
6. Harris WS, von Schacky C. The Omega-3 Index: a new risk factor for death from coronary heart disease? 2004. PubMed 15208005; Stark KD. Global survey of the omega-3 fatty acids DHA and EPA in the blood stream of healthy adults. 2016. PubMed 27216485.
7. Great Britain nutrition and health claims (NHC) register. gov.uk.
8. Sarter B. Blood DHA and EPA in vegans and effects of an algal-derived omega-3 supplement. 2015. PubMed 24679552.
9. Plourde M, Cunnane SC. Extremely limited synthesis of long chain polyunsaturates in adults. 2007. PubMed 17622276.
10. Simmonds LA. Omega-3 fatty acid supplementation in pregnancy: baseline omega-3 status and early preterm birth. 2020. PubMed 32034969.
11. DREAM Research Group. n-3 fatty acid supplementation for the treatment of dry eye disease. 2018. PubMed 29652551.
12. Appleton KM. Omega-3 fatty acids for depression in adults. Cochrane, 2021. PubMed 34817851.
13. Okereke OI. Marine omega-3 fatty acids vs placebo and risk of depression (VITAL-DEP). 2021. PubMed 34932079.
14. Lee YH. Omega-3 polyunsaturated fatty acids and the treatment of rheumatoid arthritis: a meta-analysis. 2012. PubMed 22835600.
15. Bath-Hextall FJ. Dietary supplements for established atopic eczema. Cochrane, 2012. PubMed 22336810.
16. Brainard JS. Omega-3, omega-6 and polyunsaturated fat for cognition: meta-analysis. 2020. PubMed 32305302.
17. Arterburn LM. Algal-oil capsules and cooked salmon: nutritionally equivalent sources of docosahexaenoic acid. 2008. PubMed 18589030.

This article is general information, not medical advice. If you have symptoms that worry you, are pregnant or breastfeeding, or take an anticoagulant or other regular medicine, speak to your GP or pharmacist before adding an omega-3 supplement.