Do oxidized omega-3s in fish oil lose their ability to prevent LDL oxidation?

What we’ve found so far is based on one clear assertion from laboratory research, with no conflicting data in our review. The evidence we’ve reviewed leans toward the idea that oxidation reduces the effectiveness of omega-3s in preventing LDL oxidation, at least in test tube environments. We don’t know yet how this translates to the human body, since these findings come from lab tests, not human trials. It’s also unclear how much oxidation occurs in typical fish oil supplements during storage or after opening, or whether the body can compensate in other ways.

For now, the data points to a simple practical takeaway: if you take fish oil supplements, check the expiration date, store them in a cool, dark place, and avoid using them if they smell fishy or rancid. Freshness may help preserve their intended biological activity.