What are the potential side effects of taking omega-3 fish oil?

The leaflet by frequency at the standard dose, from very common down to uncommon

What are the potential side effects of taking omega-3 fish oil is a question a medicine answers with a leaflet, graded by frequency, and a supplement answers with a shelf, which grades nothing, so the honest page writes the leaflet a standard shelf softgel would carry if supplements had them, using the medicine leaflet's frequency bands and the trials' evidence for each. Very common, more than one person in ten: nothing. There is no side effect that most people taking a standard softgel a day experience, the outcome trials at three times that dose for years recording gut complaints as minor and in a minority, the cardiovascular outcome literature's safety record, so the top band of the leaflet is empty, which is unusual among the things a lifter swallows. Common, between one in ten and one in a hundred: belching, the fishy repeat, and only when the softgel is taken on an empty stomach or just before a meal that has not arrived, the oil floating on the stomach contents beneath the sphincter, the reflux-and-posture literature's mechanism, with the same softgel taken in the middle of a meal moving belching down to rare, so the one common side effect on the leaflet is conditional on a timing the leaflet's dosing instruction would tell the reader to avoid. Uncommon, between one in a hundred and one in a thousand: nausea, again when fasted, and a fishy aftertaste that lasts an hour or two, both of them fixed by the meal and, where they persist, by a fresh tub checked by the bite test, a rancid oil moving both up the bands and being a storage fault rather than a fish oil property.

The rare and dose-related band, the not-seen band, the interactions and overdose lines, and the leaflet filed

Rare at the standard dose and dose-related above it, the band a leaflet would print in the smallest type and the one the shelf reader most needs: loose, greasy or urgent stools, which do not occur at a standard softgel and appear at two grams a day and above when more fat arrives than the small intestine absorbs, the too-much pages' first sign; easier bruising and a shaving nick that bleeds a little longer, the platelet effect, which appears at around three grams and above and stayed minor in every trial, never becoming an organ bleed; a small rise in LDL cholesterol on a blood test at two grams and above, more with DHA-heavy oils; and the atrial fibrillation signal, a dose-related increase in a rhythm problem most evident at four grams a day, roughly one extra case per hundred over years at that dose and small or absent below a gram, the atrial fibrillation meta-analyses' finding, which is the reason the four-gram rung is a prescriber's. Not seen at any dose studied, the band a leaflet does not print and a reader most wants: liver injury, the liver injury registry grading fish oil as an unlikely cause with no cases; kidney harm, none; weight gain, at nine calories a softgel none; hair, skin or nail effects, none; mood or hormone changes in the well, none; and dependence, tolerance or withdrawal, none, a fat that builds into membranes having no receptor. The interactions line: anticoagulants and dual antiplatelet therapy at a gram or more, where bleeding time lengthens slightly and the clinician is told, and orlistat, which blocks the absorption of the oil, with nothing for statins, blood pressure tablets, caffeine, creatine or protein. The overdose line: five grams of EPA and DHA a day is the safe level for supplements, sixteen standard softgels, above every band on the page. The dosing instruction that shrinks the leaflet: one softgel in the middle of a meal, from a tub stored cool and dark and checked by the bite test, which moves belching and nausea to rare and leaves the standard-dose leaflet with nothing common at all. The leaflet filed: an empty very-common band, belching when fasted as common, fasted nausea and aftertaste as uncommon, loose stools, bruising, an LDL nudge and the rhythm signal as rare and dose-related above the standard dose, nothing seen for liver, kidney, weight, hair, mood or hormones, anticoagulants and orlistat as the interactions, and five grams as the ceiling, with the worked example being the softgel the leaflet describes, £14.99 for 90 at 17p.

The verdict, a leaflet whose top band is empty and whose serious band belongs to doses a shelf reader does not take

What are the potential side effects of taking omega-3 fish oil: written as the leaflet a shelf softgel would carry, nothing in the very common band, belching when the softgel is taken fasted in the common band and moved to rare by the middle of a meal, fasted nausea and a fishy aftertaste in the uncommon band, and a rare and dose-related band above the standard dose of loose stools at two grams, easier bruising and an LDL nudge at two to three grams and the atrial fibrillation signal at four grams, with liver injury, kidney harm, weight gain, hair, skin, mood, hormone and dependence effects not seen at any dose studied, anticoagulants at a gram or more and orlistat as the interactions, and five grams as the safe level, so that one softgel mid-meal from a fresh tub leaves a leaflet with nothing common on it. The softgel the leaflet describes: Futuro Labs Omega 3 Fish Oil, one mid-meal, 180mg EPA and 120mg DHA, lab-tested purity, 90 for £14.99 at 17p a day.

What to check on the label

Questions people also ask

What is the most common side effect of fish oil?

Belching, the fishy repeat, and only when a softgel is taken on an empty stomach or just before a meal that has not arrived, the oil floating beneath the sphincter, so it sits in the common band for a fasted softgel and drops to rare for one taken in the middle of a meal, which is the whole of the dosing instruction.

Are there any serious side effects of fish oil?

At the standard dose none: the serious band is dose-related and belongs to the high rungs, easier bruising at three grams and above that stayed minor in every trial, and a dose-related atrial fibrillation signal most evident at four grams, roughly one extra case per hundred over years at that dose and small or absent below a gram, which is why four grams is a prescriber's rung.

Does fish oil have long-term side effects?

None seen at any dose studied: the outcome trials gave a gram a day to tens of thousands of people for years and recorded minor gut and bleeding effects, the liver injury registry grades fish oil an unlikely cause with no cases, and there is no kidney harm, weight gain, hair, skin, mood or hormone effect and no dependence, tolerance or withdrawal for a fat that builds into membranes.

What does fish oil interact with?

Two things: anticoagulants and dual antiplatelet therapy at a gram or more of EPA and DHA, where bleeding time lengthens slightly and the clinician is told, and orlistat, which blocks the lipase that absorbs the oil, so the two are separated in time, with no interaction for statins, blood pressure tablets, caffeine, creatine or protein.

How much fish oil is an overdose?

The safe level for supplemental EPA and DHA is five grams a day, sixteen standard softgels, which no reader reaches by accident, and every side effect on the leaflet sits below it in a dose-related order, the gut at two grams, bruising at three and the rhythm signal at four, with the four-gram rung belonging to a prescriber.

Sources

1. The large cardiovascular outcome trials of omega-3: around a gram a day of EPA and DHA in primary-prevention populations produced no meaningful reduction in major cardiovascular events, while four grams of purified EPA in people with raised triglycerides on statins reduced events in one large trial, so the supplement-dose story is maintenance and the treatment-dose story is a prescription. PubMed record
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. The drug-induced liver injury reference: fish oil and omega-3 fatty acid preparations, including the prescription ethyl esters at four grams a day, have not been linked to clinically apparent liver injury in the trials or in case reports, are graded as unlikely causes of liver injury, and if anything reduce liver fat and enzymes in fatty liver disease, with vitamin A excess from cod liver oil being the separate and documented hepatic hazard. https://www.ncbi.nlm.nih.gov/books/NBK548176/
4. 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

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