Fish oils, high in omega-3 polyunsaturated fatty acids (n-3 PUFAs), are among the most popular dietary supplements worldwide, with millions of people consuming them regularly. Omega-3 fish oils are commonly associated with a wide range of potential health benefits, including cardiovascular disease prevention, reduced cognitive decline and better management of inflammatory conditions such as arthritis, inflammatory bowel disease and asthma.
A 2023 study of 72 store shelf products found that many omega-3 fish oil supplements sold in the U.S. are oxidised - meaning they have gone rancid. This issue is especially prevalent in flavoured supplements, with 68% exceeding acceptable oxidation levels. Even unflavoured products weren’t exempt, with 13% showing signs of rancidity. Flavoured supplements may mask the unpleasant taste, making it harder for consumers to detect issues.
A similar 2015 New Zealand study found that only 8% of products met the international recommendations for oxidisation, and that overall concentrations of EPA and DHA were considerably lower than claimed by labels.
As ever, please talk to your doctor or medical practitioner most familiar with your medical history before implementing any changes in diet, exercise or lifestyle, especially if you are under treatment. Links to supporting studies and resources are shared at the end of page.
Why Does Rancidity Happen?
Omega-3 oils are highly sensitive to oxygen and environmental conditions like heat and humidity. Improper storage, long shelf times, and poor handling in the supply chain contribute to the problem. Once oxidised, omega-3 oils lose their health benefits and may even pose risks.
What Can Consumers Do?
Check freshness: Crack open a capsule and smell it. A sour or fishy smell is a sign of rancidity.
Store properly: Keep supplements in the fridge or freezer to slow oxidation.
Buy smart: Purchase 'tested' products from reputable suppliers, avoid stockpiling and use supplements sooner rather than later.
Is Eating Fish a Better Option?
Whole, oily, fish provide greater health benefits than supplements. Not only for their oils but also due to the additional nutrients and the benefits of overall dietary changes associated with eating fish.
We make it a point to eat oily fish twice per week. Tinned sardines (on toast or in a pasta) and frozen mackerel (simply grilled, with rosemary) are a popular menu item at home, easy to store and to cook. Fresh fish, such as (local to Singapore) kembong or selar are delicious, and also relatively easy to cook.
In Singapore a 2015 study by Duke-NUS Graduate Medical School and the Saw Swee Hock School of Public Health found that individuals in the top 25% of omega-3 fatty acid consumption - derived from seafood such as fish and shellfish, as well as plant-based sources like seeds, nuts, and grains - had a 17% lower risk of death from cardiovascular complications compared to those in the lowest 25% of omega-3 intake.
Final Thoughts
While high-quality supplements can be effective, many fail to meet safety and efficacy standards, leaving consumers disappointed and out of pocket. The takeaway? If you’re relying on fish oil supplements, prioritise quality and 'freshness', or, consider adding fish to your diet for a more reliable source of omega-3s and overall nutrition.
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Alastair
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Related Studies
The 2023 study in question... Hands JM, Anderson ML, Cooperman T, Frame LA. A Multi-Year Rancidity Analysis of 72 Marine and Microalgal Oil Omega-3 Supplements. J Diet Suppl. 2024;21(2):195-206. doi: 10.1080/19390211.2023.2252064. Epub 2023 Sep 15. PMID: 37712532.
Dinu M, Sofi F, Lotti S, Colombini B, Mattioli AV, Catapano AL, Casula M, Baragetti A, Wong ND, Steg PG, Ambrosio G. Effects of omega-3 fatty acids on coronary revascularization and cardiovascular events: a meta-analysis. Eur J Prev Cardiol. 2024 Nov 11;31(15):1863-1875. doi: 10.1093/eurjpc/zwae184. PMID: 38869144.
Wei BZ, Li L, Dong CW, Tan CC; Alzheimer’s Disease Neuroimaging Initiative; Xu W. The Relationship of Omega-3 Fatty Acids with Dementia and Cognitive Decline: Evidence from Prospective Cohort Studies of Supplementation, Dietary Intake, and Blood Markers. Am J Clin Nutr. 2023 Jun;117(6):1096-1109. doi: 10.1016/j.ajcnut.2023.04.001. Epub 2023 Apr 5. PMID: 37028557; PMCID: PMC10447496.
Kosti RI, Kasdagli MI, Kyrozis A, Orsini N, Lagiou P, Taiganidou F, Naska A. Fish intake, n-3 fatty acid body status, and risk of cognitive decline: a systematic review and a dose-response meta-analysis of observational and experimental studies. Nutr Rev. 2022 May 9;80(6):1445-1458. doi: 10.1093/nutrit/nuab078. PMID: 34605891.
Khan SU, Lone AN, Khan MS, Virani SS, Blumenthal RS, Nasir K, Miller M, Michos ED, Ballantyne CM, Boden WE, Bhatt DL. Effect of omega-3 fatty acids on cardiovascular outcomes: A systematic review and meta-analysis. EClinicalMedicine. 2021 Jul 8;38:100997. doi: 10.1016/j.eclinm.2021.100997. PMID: 34505026; PMCID: PMC8413259.
Albert BB, Derraik JG, Cameron-Smith D, Hofman PL, Tumanov S, Villas-Boas SG, Garg ML, Cutfield WS. Fish oil supplements in New Zealand are highly oxidised and do not meet label content of n-3 PUFA. Sci Rep. 2015 Jan 21;5:7928. doi: 10.1038/srep07928. Erratum in: Sci Rep. 2016 Nov 07;6:35092. doi: 10.1038/srep35092. PMID: 25604397; PMCID: PMC4300506.
Koh AS, Pan A, Wang R, Odegaard AO, Pereira MA, Yuan JM, Koh WP. The association between dietary omega-3 fatty acids and cardiovascular death: the Singapore Chinese Health Study. Eur J Prev Cardiol. 2015 Mar;22(3):364-72. doi: 10.1177/2047487313517576. Epub 2013 Dec 16. PMID: 24343844; PMCID: PMC4501020.
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