Fish oil is one of the more storage-sensitive supplement categories. The polyunsaturated fatty acids in it — including EPA and DHA — are prone to oxidation, and exposure to light, warmth and air speeds this process up. Oxidised fish oil develops a rancid smell and taste and loses its value, so storage genuinely affects what you get from the product.
Practical guidelines:
- Keep the jar tightly closed — every opening lets in fresh air, so do not leave the lid off.
- Store it in a cool place, protected from light: a cupboard away from the stove and windowsill is fine. Avoid the bathroom, where humidity and temperature swings are common.
- Keep it out of the reach of children — soft, smooth capsules can look appealing to a child.
- Respect the expiry date and finish an opened jar within a reasonable time rather than stretching it over years.
The soft gelatin capsule itself is part of the freshness strategy: it seals the oil away from air and light, which is one of the main reasons capsules are used for fish oil instead of bottled liquid oil. A simple self-check: if a capsule smells strongly rancid when you open the jar, the oil has likely degraded and the product should not be used.