Why does fish oil make you burp?

By Tom Francis·Updated 2026-09-03·2 sources·Editorial policy

The two causes

An empty stomach is the common one. A softgel taken with nothing else sits in an empty stomach and the oil is released with nothing to mix into, which produces the repeat most people associate with fish oil.

Oxidation is the other. Fish oil goes rancid with exposure to air, heat and light, and oxidised oil tastes and smells considerably worse. That is a storage problem rather than a product one, though a poor quality oil starts closer to the line.

What actually reduces it

Taking it with a meal, which is the single largest improvement and costs nothing. Keeping the tub in a cupboard rather than on a windowsill or in a car. And a deodorised softgel, which seals each dose until it is swallowed rather than exposing a whole bottle of liquid to air.

Futuro Labs Omega 3 Fish Oil is a deodorised mini softgel providing 180mg EPA and 120mg DHA, which is 300mg combined at one capsule for 17p a day. One capsule also means nothing to split, which matters because splitting a dose is the usual workaround for products needing three.

When it is worth acting on

A strong fishy smell when the tub is opened, or an off taste from a capsule that has broken, both suggest the oil has oxidised. That is a reason to replace it rather than to persist.

Very few consumer products publish peroxide or anisidine values, which are the standard oxidation measures, so taste and smell are the practical proxy. A tub kept properly should be fine through its stated life.

The full version

• Fish oil before or after training?Why storage matters more than timing.
• How to check what purity testing a fish oil has actually hadIncluding oxidation markers and what the testing words mean.

Questions players ask

Sources

• EFSA register of nutrition and health claims
• Food supplements guidance, gov.uk