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How can I tell if my fish oil supplement is rancid?

Question:
How can I tell if my fish oil supplement is rancid (oxidized) or spoiled? And if it is spoiled, is it still safe to take?

Answer:
Fish oil which is rancid or oxidized may have an unpleasant odor and taste, although it would be hard to tell if you are taking a softgel. Oxidized fish oil may also raise levels of LDL "bad" cholesterol, as explained in the "Quality Concerns" section of our Fish Oil and Omega-3 Fatty Acid Supplements Review.

To find a fish oil supplement that has been shown to be fresh and not rancid, see the Results table in our fish oil review and look for products that received a checkmark in the "Freshness" column.

Some studies have suggested that oxidation of fish oil in supplements is common. These studies have generally not taken into account the fact that the citrus flavoring added to fish oil supplements can interfere with oxidation tests and falsely indicate that an oil is oxidized. ConsumerLab factors this possibility into its reporting to avoid mischaracterizing the quality of a product.

Be sure to also see our tips for storing and keeping your fish oil supplement fresh.

Learn more about choosing the best fish oil supplement and keeping fish oil fresh:



Is it safe to consume fish oil as a long-term food supplement? >>

I heard that some types of fish oil are esterified and can dissolve plastic foam (polystyrene or Styrofoam). Is this right and, if so, should I be concerned? >>

Are there any red flags to look for on the label when choosing a fish oil supplement? >>

Is it okay to freeze fish oil to keep it from becoming rancid? >>



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This CL Answer initially posted on 11/11/2017.

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