What's the downside of fish oil?

The downsides ranked on two axes, the common and trivial ones first, then the common-at-high-dose ones and the quality one

What is the downside of fish oil, and the long list of variants asking about side effects, negatives and harms, is answered by ranking the downsides on two axes, how common and how serious, because the common ones are trivial and the serious ones are rare or specific, and a reader who confuses the two either abandons a useful habit or ignores a real note. Common and trivial: fishy burps and reflux, the oil floating on an empty stomach and coming back up, experienced by a large share of new users and fixed by the burp pages' rungs, a softgel in the middle of a meal, an upright hour or two after, a frozen softgel, a smaller one or, as the premium fix, an enteric coat, a downside of comfort rather than health. Common at high doses: loose stools, a gram or two of oil a day loosening the gut in some people and several grams in most, and a persistent fishy taste, both fixed by splitting a high dose across meals and both absent at a standard softgel, the high-dose page's territory. The quality downside, which is the one most readers meet without knowing: a rancid oil, oxidised in the tub by heat, light and air, tasting of paint or old nuts, burping worst of all and delivering oxidised fat rather than omega-3, the retail surveys finding a meaningful share of shelf oils over the monograph's TOTOX limit, fixed by a fresh tub with a recent date, stored cool and dark with the lid closed, finished within a couple of months, checked by biting a softgel and, for the certificate reader, by a TOTOX under 26, the downside that is a reason to buy well rather than a reason not to buy.

The rare or specific downsides, the things that are not downsides, and the two axes filed

Rare or specific, the downsides that are real for particular readers and irrelevant to most. The antiplatelet note: EPA and DHA modestly reduce platelet stickiness, an effect small at supplement doses and not associated with clinically important bleeding in trials up to five grams in healthy adults, but one a reader on warfarin, a direct oral anticoagulant, aspirin or clopidogrel mentions to the prescriber, especially at gram-and-above doses, and one the surgical team is told of before an operation. The LDL rise: at the triglyceride-lowering doses of two grams and more, some people see a modest rise in LDL cholesterol alongside the fall in triglycerides, the lipid literature's consistent finding and a reason the two-gram claim is taken with a GP who can see the lipid panel. The atrial fibrillation signal: meta-analyses of the cardiovascular outcome trials find a dose-related rise in atrial fibrillation risk, most evident at four grams a day, present at around two and small or absent below a gram, the honest ceiling for a healthy adult and a reason the high rungs need a reason. Vitamin A: a body-oil fish oil carries none, but a cod liver oil carries hundreds of micrograms of preformed vitamin A a capsule and beside a multivitamin can approach the 3000 microgram upper level, with pregnancy avoiding liver oils altogether. And the sustainability question, an ethical downside for a reader who cares, answered by a scheme's logo on the tub. The things that are not downsides deserve naming because the folklore lists them: dependence and tolerance, which a fat that builds into membranes over months does not produce, stopping simply letting the index fall; weight gain, a softgel being about nine calories; blood thinning at standard doses, the antiplatelet effect being a note for medicine-takers rather than a property a healthy adult feels; and any effect on the liver, kidneys or hormones, none of which the trials or the pharmacovigilance record show at supplement doses. The two axes filed: burps and reflux common and trivial, loose stools and a fishy taste common at high doses, a rancid oil the quality downside, and the antiplatelet note, the LDL rise, the atrial fibrillation signal and liver-oil vitamin A rare or specific, with dependence, weight gain and blood thinning not downsides at all, and the worked example being a standard dose that sits below every serious one, a lab-tested body oil, one softgel at 17p, £14.99 for 90.

The verdict, trivial downsides that are common, serious ones that are rare, and a rancid tub in between

What is the downside of fish oil: ranked on two axes, the common downsides are trivial, fishy burps and reflux fixed by a mid-meal softgel and an upright hour, loose stools and a fishy taste at high doses fixed by a split, and the serious downsides are rare or specific, the antiplatelet note for anticoagulant users and before surgery, an LDL rise in some people at the triglyceride-lowering doses, the dose-related atrial fibrillation signal most evident at four grams, and vitamin A in liver oils beside a multivitamin or in pregnancy, with a rancid oil the quality downside in between, common on the shelf and fixed by buying and storing well, and dependence, weight gain and blood thinning at standard doses being folklore rather than downsides. A standard lab-tested body oil below every serious one: Futuro Labs Omega 3 Fish Oil, one softgel with food, 180mg EPA and 120mg DHA, 90 for £14.99 at 17p a day.

What to check on the label

Questions people also ask

What are the side effects of taking fish oil every day?

At a standard softgel, fishy burps and reflux for some new users, fixed by taking it mid-meal and staying upright; at high doses, loose stools and a fishy taste; and for specific readers, an antiplatelet note on anticoagulants, an LDL rise at two grams and more and a dose-related atrial fibrillation signal most evident at four grams.

Is it harmful to take fish oil daily?

Not at a standard dose for a healthy adult: the trials up to five grams find no organ harm, the practical range of 250mg to a gram carries only burps, and the serious notes, atrial fibrillation and an LDL rise, belong to the high rungs, with a rancid oil being the everyday harm a reader avoids by buying fresh and storing cool.

Does fish oil thin the blood?

Modestly at the platelet level, an effect small at supplement doses and not associated with clinically important bleeding in trials up to five grams in healthy adults, but one a reader on warfarin, a direct oral anticoagulant, aspirin or clopidogrel mentions to the prescriber and the surgical team is told of before an operation.

Can fish oil cause heart problems?

At high doses, a signal: meta-analyses of the cardiovascular outcome trials find a dose-related rise in atrial fibrillation risk, most evident at four grams a day and small or absent below a gram, so the high rungs need a reason and a GP while a standard softgel sits below the signal.

What is the most common problem with fish oil that people don't notice?

A rancid tub: oxidised by heat, light and air, tasting of paint, burping worst and delivering oxidised fat rather than omega-3, common on the shelf in retail surveys and avoided by a fresh tub stored cool and dark, finished within a couple of months, with a bite test or a TOTOX under 26 as the check.

Sources

1. EFSA Panel on Dietetic Products. Scientific opinion on the tolerable upper intake level of EPA, DHA and DPA: supplemental intakes of EPA and DHA combined up to about 5g/day do not raise safety concerns for adults. EFSA Journal 2012;10(7):2815. https://www.efsa.europa.eu/en/efsajournal/pub/2815
2. Meta-analyses of cardiovascular outcome trials of marine omega-3: a dose-related increase in the risk of atrial fibrillation, most evident at doses of four grams a day and small or absent below one gram, a finding that sets the honest ceiling of high-dose omega-3 for a healthy adult. PubMed record
3. Meta-analytic evidence on omega-3 fatty acids and LDL cholesterol: triglyceride lowering is the consistent effect, with LDL unchanged or modestly raised, particularly with DHA-containing preparations. PubMed record
4. The fish oil oxidation literature: oxidation is measured by peroxide value, anisidine value and their combination as TOTOX, with the industry monograph setting limits of 5, 20 and 26 respectively, and surveys of retail fish oils finding a meaningful share above those limits, freshness being a quality dimension a label rarely shows and a certificate does. PubMed record

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