Of 47 fish oil supplements tested in New Zealand, 86% met the industry standard for secondary oxidation, but flavoring agents caused many products to falsely appear oxidized when tested with standard methods.
Evidence from Studies
No evidence studies found yet.
What Would Prove This
Per GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this claim, ordered from strongest to weakest.
A systematic review of all studies comparing p-AV and TAV measurements in flavored fish oils would determine whether flavor interference consistently causes overestimation of secondary oxidation.
A systematic review and meta-analysis of all peer-reviewed studies (2000–2024) that measured both p-AV and TAV (or other flavor-resistant methods) in flavored fish oil supplements, with inclusion criteria of paired measurements and clear labeling of flavor type. Primary outcome: mean difference in p-AV vs. TAV values.
A longitudinal cohort comparing p-AV and TAV results in the same flavored fish oil products over time would determine whether interference is stable or changes with storage.
A prospective cohort study of 50 flavored fish oil supplements, with p-AV and TAV measured at baseline, 6, 12, and 24 months under ambient storage. Primary outcome: correlation between p-AV and TAV over time and rate of divergence.
A cross-sectional study comparing p-AV and TAV results across flavored and unflavored products would confirm whether flavoring is the primary driver of false positives.
A cross-sectional study of 100 fish oil supplements (50 flavored, 50 unflavored) from multiple brands, with both p-AV and TAV measured using validated methods. Primary outcome: proportion of flavored products with p-AV >20 but TAV <70%.
A case series of flavored products with high p-AV but low TAV could identify which flavor compounds cause the most interference.
A case series of the 15 flavored products in this study with p-AV >20 but TAV <70%, with chemical analysis of flavoring ingredients to identify specific compounds (e.g., citrus oils, mint) causing assay interference.
Expert consensus on whether p-AV should be used for flavored products could inform regulatory updates to avoid misleading compliance assessments.
A Delphi consensus process involving 12 analytical chemists and regulatory experts to determine whether p-AV should be prohibited for flavored fish oils and whether TAV or other methods should be adopted as standard.