How to minimise fish oil aftertaste

Learn how to reduce fish oil aftertaste, and whether smell means poor quality. Tips for comfortable daily omega-3 supplementation.

Fishy aftertaste is a common complaint people have about fish oil supplements, and one of the reasons people may stop taking them. The irony is that the very thing driving people away from omega-3 supplementation is often a solvable problem, and sometimes a sign of something worth paying attention to.

This article explains what causes fish oil burps, what a fishy smell can and cannot tell you about supplement quality, and practical steps that can make daily omega-3 use more comfortable.

What causes fishy burps and aftertaste?

When you swallow a fish oil capsule, it travels to your stomach, where the softgel shell begins to dissolve. As the oil is released, it separates from the watery stomach contents and rises to the surface. Oil is less dense than stomach fluid, so it naturally floats upward toward the lower oesophageal sphincter (LES), the valve between the stomach and oesophagus.

When the LES relaxes during a normal burp, small amounts of floating oil can travel back up, carrying a fishy taste and smell with it. This is a mechanical process, not a sign of allergy or intolerance.

Taking fish oil on an empty stomach slows its transit through the digestive tract, giving the oil more time to sit near the LES. Capsule quality, oil freshness, and individual differences in stomach acid levels all play a role. People with lower stomach acid production, which is more common in older adults and those on acid-suppressing medications, may notice fish oil aftertaste more frequently.

Does a fishy smell mean the oil is bad or oxidised?

Not always, but it can be a useful indicator. Fresh, high quality fish oil has a mild, slightly oceanic scent. A strong, pungent, or sour smell is a different matter and can indicate oxidation.

Omega-3 fatty acids are polyunsaturated, which makes them susceptible to oxidation when exposed to air, heat, or light. When EPA and DHA oxidise, they break down into peroxides and aldehydes, which are responsible for the smell and taste of rancid fish oil. The omega-3 industry measures freshness using a metric called the TOTOX value (total oxidation). The Global Organization for EPA and DHA Omega-3s (GOED) sets a voluntary maximum TOTOX limit of 26 for quality fish oils.

A 2017 study published in Scientific Reports tested 47 fish oil products in New Zealand and found that 77% met the voluntary GOED TOTOX limit, with 96% meeting the less stringent limits set by the Australian TGA and European Pharmacopeia. A separate study in 2016 confirmed that Australian and New Zealand fish oil products met label claims for omega-3 content and were not heavily oxidised.

The majority of fish oil supplements sold in Australia meet regulatory quality standards. If your capsules smell strongly fishy or sour, break one open and smell the oil directly. A sharp, unpleasant odour may be a sign to replace the bottle.

How to reduce fish oil burps

Take fish oil with food

This is one of the most effective strategies. A 2015 study published in the Journal of the Academy of Nutrition and Dietetics found that omega-3 absorption increased significantly when taken with a fat-containing meal. Fat stimulates bile release and digestive enzyme activity, helping the oil move through the stomach into the small intestine more quickly. Even a modest amount of fat from eggs, avocado, or olive oil is enough.

Split your dose

If you are taking two or more capsules a day, splitting them across meals reduces the volume of oil in the stomach at any one time. One capsule at breakfast and one at dinner may help compared to taking both at once.

Adjust your timing

Taking capsules before bed means any aftertaste occurs during sleep. If you are new to fish oil, starting with one capsule per day and gradually increasing to the recommended dose can also give your digestive system time to adjust.

Odourless and mini capsules: why format matters

Odourless formulations use natural flavouring agents, such as lemon or vanilla oils, to neutralise the fishy scent by reducing the volatile compounds that carry fishy flavour during digestion.

Blackmores Fish Oil 1000 Odourless uses natural lemon and vanilla flavouring rather than artificial surfactants. Each capsule provides 300 mg of omega-3 (180 mg EPA, 120 mg DHA) sourced from 100% wild-caught small fish and tested for mercury, dioxins, and PCBs.

Capsule size also plays a role. Smaller capsules pass through the stomach more quickly, reducing the window for oil release. Blackmores Fish Oil Mini Caps Odourless contain concentrated omega-3 triglycerides in a smaller format, delivering 300 mg of combined EPA and DHA per capsule.

Enteric-coated capsules are another option, designed to pass through the stomach intact and dissolve in the small intestine, bypassing the stage of digestion where fish oil is most likely to cause burps.

Fish oil and reflux: who may be more sensitive

Individuals with sensitive digestive systems may be more prone, as lower stomach acid means the softgel capsule breaks down more slowly. Very large or fatty meals can also contribute by relaxing the LES, so taking fish oil with a moderate meal helps. If reflux persists despite trying these strategies, speaking with a healthcare professional is a sensible next step.

Storage mistakes that can worsen aftertaste

Omega-3 fatty acids oxidise faster when exposed to heat, light, and air, meaning poor storage can turn a fresh bottle rancid before its expiry date. Store capsules in a cool, dry place away from direct sunlight. Many people keep fish oil in the fridge, which slows oxidation and keeps the oil fresher. Keep the lid tightly sealed after each use, and if you buy large count bottles, consider whether a smaller pack size would mean finishing the bottle sooner with less air exposure.

Check the expiry date before purchasing. If you open a capsule and notice a strong, unpleasant smell, replace the bottle regardless of the date on the label.

Quality indicators that improve tolerance

Look at the EPA and DHA content per capsule, not just the total fish oil amount. A capsule labelled "1000 mg fish oil" may contain as little as 300 mg of actual omega-3s. Higher-concentration formulas mean fewer capsules and less oil in the stomach. Check whether the manufacturer tests for oxidation and contaminants, and whether the oil is sourced from wild-caught small fish using processes that minimise heat and oxygen exposure.

Key takeaways

Fishy aftertaste from fish oil supplements is common and usually manageable. Taking fish oil with food, refrigerating capsules, splitting doses, and choosing odourless or smaller format capsules can all reduce or eliminate the issue. If a fishy smell persists despite good storage and a quality product, the oil may have oxidised, and replacing the bottle is the right call.

Consistent daily use with a format that works for you is more valuable than a higher dose approach that you cannot stick with.

Frequently asked questions

Why does fish oil cause fishy burps?

Fish oil is less dense than stomach fluid, so it floats to the top after the capsule dissolves. When the oesophageal valve relaxes during a burp, small amounts of oil travel upward carrying a fishy taste. Taking capsules with food helps the oil move through the stomach more quickly.

Does fish oil aftertaste mean it has gone bad?

Not necessarily. Some aftertaste is a normal side effect of how fish oil is digested. A strong, sour smell when you break open a capsule is a better indicator of rancidity. If the oil smells unpleasant when tested directly, replace the bottle.

How can I minimise fish oil burps?

Take capsules with a meal containing some fat. Refrigerate or freeze capsules to slow their breakdown. Split your dose across meals and consider an odourless or enteric-coated formulation if standard capsules cause persistent issues.

Is odourless fish oil better?

Odourless formulations use natural flavouring to reduce fishy taste during digestion. They contain the same omega-3 content as standard capsules. For people who experience regular aftertaste, an odourless format can make supplementation more comfortable.

Should fish oil be taken with food?

Yes. Fish oil is best absorbed with a meal containing some dietary fat. Eating alongside your capsule also helps move the oil through the stomach more efficiently, reducing the chance of reflux.

What should fish oil smell like?

Fresh fish oil has a mild, faintly oceanic scent. It should not smell strongly of fish, sour, sharp, or chemical. Break open a capsule to test. A clean, mild scent means the oil is fresh.

Is fish oil still worth taking if it causes reflux?

For most people, yes. Reflux from fish oil is a tolerance issue, and it is usually solvable with changes to timing, format, or product. Finding a format that works for you is worth the effort.

Always read the label and follow the directions for use.

Disclaimer: This article provides general information only and is not intended to diagnose, treat, cure, or prevent any disease. The information presented is not a substitute for professional medical advice. If you have concerns about your health, please consult your GP or healthcare provider for personalised assessment and recommendations. Supplements should not replace a balanced diet.