Storage
How to Store Fish Oil
Fish oil contains highly unsaturated fatty acids that can gradually oxidize when exposed to oxygen, heat and light. Proper storage therefore helps preserve freshness and reduce the development of rancid odors and flavors.
Follow the Product Label First
There is no universal storage rule for every fish oil supplement. Some products are formulated for room-temperature storage, while liquid fish oils may recommend refrigeration after opening.
The manufacturer’s instructions on the bottle should therefore take priority over general advice.
Storing Fish Oil at Room Temperature
Fish oil capsules that are labeled for room-temperature storage should be kept in a cool, dry location away from direct sunlight and heat sources.
A closed cabinet is generally preferable to a sunny kitchen counter, a windowsill or a location close to an oven or radiator.
The container should also remain tightly closed. Each time a bottle is left open, fresh oxygen can enter and contribute to oxidation.
Refrigerating Fish Oil
Many liquid fish oil products recommend refrigeration after opening. Lower temperatures can slow chemical reactions involved in oxidation and may help an opened bottle remain fresh for longer.
Some capsules can also be refrigerated if permitted by the manufacturer. Refrigeration may change the appearance or viscosity of the oil without necessarily indicating that the product is damaged.
Should Fish Oil Be Frozen?
Fish oil does not need to be routinely stored in a freezer unless the manufacturer specifically recommends it. Freezing is not a substitute for good packaging, appropriate processing or following the product’s stated expiration and storage instructions.
Different fish oils have different fatty-acid compositions and may become cloudy, thicken or partially solidify at low temperatures. These changes alone are not a reliable test of quality or purity.
Light, Heat and Oxygen
Three important factors accelerate oxidation of omega-3 oils:
- Oxygen: repeated exposure to air can promote oxidation.
- Light: direct sunlight and strong light can accelerate deterioration.
- Heat: prolonged exposure to elevated temperatures can reduce stability.
For these reasons, keeping the bottle tightly closed and away from heat and sunlight is useful regardless of whether the product is stored in a refrigerator or at room temperature.
How to Recognize Rancid Fish Oil
A strong rancid, sour or unusually unpleasant smell or taste can indicate deterioration. Fish oil naturally has some marine flavor, so not every fishy smell means the product is rancid, but a substantial change after opening deserves attention.
If a product smells or tastes noticeably different from when it was first opened, has been stored improperly for a long period or is far beyond its expiration date, replacing it is generally preferable to continuing to use it.
The susceptibility of EPA- and DHA-rich oils to oxidation is well documented; exposure to light, heat and oxygen can accelerate lipid peroxidation. Research on oxidation of marine omega-3 supplements discusses these factors in more detail.