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1 thing everyone needs to check before taking omega 3: Oxidation
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Summary
- Omega 3 fish oil can oxidise, which causes changes in how the oil looks and a rancid fish smell.
- Oxidation can lead to digestive issues and potentially more severe conditions, however, studies in humans are needed to confirm what was found in animal ones.
- Vegan omega 3 from algae oil works just as well as fish oil, and may be less prone to oxidation.
- brain feed's plant-based omega 3 DHA has some of the best oxidation data in the sector with all the values of oxidation well below the threshold even at 12 months.
Fish oil is one of the world's most popular dietary supplements, taken daily by millions of people for its brain health, cardiovascular, and anti-inflammatory benefits. Behind the glossy capsule and bold health claims lies an urgent scientific debate: does fish oil go bad, and what actually happens when it does?
How do I know if my fish oil is bad?
Oxidation is the process by which the omega 3 fats DHA and EPA react with oxygen, breaking down into a cascade of chemical compounds called lipid peroxides1 Trusted Source 2020 - Foods (Basel, Switzerland) Research evaluation Chemical Compositional Changes in Over-Oxidized Fish Oils . These molecules are responsible for that unmistakable rancid fish oil smell, and, according to a growing body of research, potentially for much more. Let’s explore how to tell if fish oil is rancid, and look at the standards that shape the best products.
How to check if fish oil is rancid?
Here are 5 ways to ensure the omega 3 oil you’re supplementing with is good.
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A strong "gone bad" fish smell means it's rancid.
The simplest test requires no laboratory equipment. Open a capsule, bite it or pierce it with a pin, and smell the oil directly. Fresh, high-quality fish oil should smell neutral to mildly oceanic, like the sea, not like an overpowering, sour, or "gone off" fish market2 Trusted Source 2012 - Lipids Human study Key lipid oxidation products can be used to predict sensory quality of fish oils with different levels of EPA and DHA . If the oil smells strongly, sour, or pungently fishy, it is almost certainly oxidised2 Trusted Source 2012 - Lipids Human study Key lipid oxidation products can be used to predict sensory quality of fish oils with different levels of EPA and DHA . A rancid taste upon consumption, or persistent fishy burping hours after taking a capsule, is a strong functional indicator of oil degradation2 Trusted Source 2012 - Lipids Human study Key lipid oxidation products can be used to predict sensory quality of fish oils with different levels of EPA and DHA .
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If it doesn’t look right, it’s probably oxidised
Beyond the at-home smell test described above, several practical signs indicate that a fish oil supplement may be past its best. Visible discolouration, oil that has darkened or turned cloudy, suggests advanced oxidation3 Trusted Source 2020 - Foods (Basel, Switzerland) Research evaluation Chemical Compositional Changes in Over-Oxidized Fish Oils . Capsules that are sticky, leaking, or smell strongly even before opening are red flags3 Trusted Source 2020 - Foods (Basel, Switzerland) Research evaluation Chemical Compositional Changes in Over-Oxidized Fish Oils . Expiration dates can be a steer, however they can also be unreliable if the starting product had high oxidation values. This means the product can oxidise well before their printed best-before date, depending on storage conditions.
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Ensure proper storage
After you have opened the product, do not store fish oil in warm or sunny locations: heat, light, and oxygen are the three primary accelerators of oxidative degradation, and even a product that left the factory compliant can become non-compliant if stored incorrectly. Once opened, keep the bottle tightly sealed, in a cool dark place, and consume within the manufacturer's recommended period, typically 3 months after opening for liquid formulations. Beware of products sold in transparent glass bottles since UV is one of the major triggers that turns omega 3 oil rancid. Instead, opt for products sold in packaging with clearly stated UV protection.
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Proof of stability
For consumers seeking objective certainty, certifications from manufacturers or third-party organisations such as IFOS (International Fish Oil Standards), or the US Pharmacopeia (USP) provide analytical verification that a product met oxidation limits at time of testing4 Trusted Source 2017 - Scientific Reports Research evaluation Omega-3 Long-Chain Polyunsaturated Fatty Acid Content and Oxidation State of Fish Oil Supplements in New Zealand . These certifications are voluntary and not universally adopted by all retailers, which is itself a meaningful signal about a brand's commitment to quality transparency.
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Beware of flavoured fish oil products
The 2024 longitudinal study found that 68% of flavoured supplements exceeded the total oxidative damage (TOTOX) limits5 Trusted Source 2024 - Journal of Dietary Supplements Research evaluation A Multi-Year Rancidity Analysis of 72 Marine and Microalgal Oil Omega-3 Supplements . This is significantly higher than their unflavoured counterparts because synthetic flavourings can chemically interfere with analytical assays and mask the sensory signs of rancidity, making it harder for both tests and taste to accurately detect oxidation[5].
What are the major side effects of omega-3 after oxidation?
When fish oil oxidises, the omega 3s break down. This degradation can reduce oil quality and potentially diminish the benefits it’s taken for. A pivotal 2013 review identified a critical gap; No human clinical trial investigating omega 3 efficacy had, at that point, reported the oxidative state of the trial oil, making it impossible to separate the effects of fresh versus oxidised oil in all previous research6 Trusted Source 2013 - BioMed Research International Systematic and meta-analysis Oxidation of marine omega-3 supplements and human health . The authors proposed that oxidised supplements could explain much of the inconsistency in the omega-3 trial literature[6].
On the other hand, animal studies have shown that chronic consumption of oxidised omega 3s can cause liver and kidney enlargement, intestinal irritation, inflammatory changes in liver tissue, and accelerated hardening of the arteries6 Trusted Source 2013 - BioMed Research International Systematic and meta-analysis Oxidation of marine omega-3 supplements and human health . Since science has yet to determine exactly what kind of effects oxidation of omega-3 can cause in humans, it’s better to avoid oxidised products.
Most noticeable omega 3 side effects are mild and manageable. The most commonly reported side effects of omega 3 supplementation are gastrointestinal: nausea, bloating, loose stools, and an unpleasant fishy aftertaste known colloquially as "fish burps"7 Trusted Source 2021 - The Journal of Nutrition Human study Pharmacokinetics of Supplemental Omega-3 Fatty Acids Esterified in Monoglycerides, Ethyl Esters, or Triglycerides in Adults in a Randomized Crossover Trial . These occur because fish oil floats on the surface of stomach contents and, when the lower ring of muscles relaxes, small amounts of oil can travel upward into the food pipe8 Trusted Source 2019 - Frontiers in Physiology Animal study Long-Chain Fatty Acid Receptors Mediate Relaxation of the Porcine Lower Esophageal Sphincter . Fresh, high-quality fish oil taken with food rarely produces these effects.
Is it better to take fish oil or vegan omega 3?
Whilst fish oil dominates the omega 3 market, algae oil offers a plant-based alternative rich in omega 3s. From an oxidation standpoint, algal oil presents several structural advantages. Because it is produced in controlled fermentation environments, rather than extracted from whole fish that have already begun to degrade post-catch, the oil can be processed immediately, under nitrogen blanket and with consistent antioxidant protection, reducing the window of oxidation exposure that plagues the conventional fish oil supply chain. It is also inherently free from concerns about heavy metal contamination, persistent organic pollutants, and fishy taste, making it a particularly attractive option for those who experience digestive sensitivity, follow a vegan or plant-based diet, or have fish allergies (noting that fish allergy reactions are typically protein-mediated, while both fish and algal oils contain only fat)9 Trusted Source 2023 - Frontiers in Microbiology Research evaluation Biotechnological production of omega-3 fatty acids: current status and future perspectives . For sustainability-conscious consumers, algal oil avoids pressure on wild fish populations entirely9 Trusted Source 2023 - Frontiers in Microbiology Research evaluation Biotechnological production of omega-3 fatty acids: current status and future perspectives . Read more about the benefits of algae oil. So, is vegan omega 3 as good as fish oil? Let’s have a look at what the official data says about brain feed’s 600mg soft capsule vegan omega 3 made from algal oil.
brain feed’s vegan omega 3: How to spot a good quality product
For both manufacturers and clinicians requiring objective measurement, three standardised assays define oil quality. The Global Organisation for EPA and DHA Omega 3 (GOED) has set the internationally recognised quality benchmarks for them10 Trusted Source 2022 - GOED Voluntary Monograph 3rd-party source GOED Voluntary Monograph (2022) .
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Measurement of primary oxidation products, which form when omega-3 first reacts with oxygen,
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Measurement of secondary oxidation products, which develop as oxidation progresses,
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The total oxidative damage, known as TOTOX, which is the most important indicator to determine the quality of omega-3.
A landmark multi-year analysis of 72 consumer omega 3 supplements actually found that up to 68% of flavoured and 13% of unflavoured products exceeded the TOTOX upper limit5 Trusted Source 2024 - Journal of Dietary Supplements Research evaluation A Multi-Year Rancidity Analysis of 72 Marine and Microalgal Oil Omega-3 Supplements . Studies across Canada, New Zealand, South Africa, and the United States found something similar: between 11% and 80% of retail products in these markets have been found to exceed at least one voluntary oxidation limit11 Trusted Source 2015 - Journal of Nutritional Science Systematic and meta-analysis Fishing for answers: is oxidation of fish oil supplements a problem? . Read more about the importance of TOTOX for high-quality omega 3.
This is precisely why stability data matters and why it’s important to transparently share them with the customers. Our latest production run maintains all values well within GOED limits, demonstrating that with the right sourcing, processing, and encapsulation standards, an omega 3 supplement can remain fresh and compliant. Third-party tested and supported by 12-month longitudinal stability data, brain feed’s omega 3 formulation is designed to deliver a fresh and clinically relevant dose of DHA.
brain feed’s oxidation values are significantly below the maximum limits set by international quality standards, indicating a fresher, higher-quality omega 3 oil with lower levels of oxidative damage.
|
brain feed baseline data |
brain feed 12-month data |
GOED benchmark values |
|
|
Primary oxidation products value |
0.08 |
2.8 |
5 |
|
Secondary oxidation products |
0.19 |
0.1 |
20 |
|
TOTOX |
0.35 |
5.7 |
26 |
It’s normal for some level of oxidation to occur in a 12 month period as omega 3s are naturally sensitive to oxidation. What's important is starting with low oxidation levels, maintaining proper storage conditions and ensuring limits remain well within GOED’s benchmark values throughout their shelf life.
Whether you choose marine or algal omega 3, the quality fundamentals remain the same: low TOTOX, independently verified freshness, and a dose sufficient to meet your health goals.
References
[1] Phung, A. S., Bannenberg, G., Vigor, C., Reversat, G., Oger, C., Roumain, M., Galano, J. M., Durand, T., Muccioli, G. G., Ismail, A., & Wang, S. C. (2020). Chemical Compositional Changes in Over-Oxidized Fish Oils. Foods (Basel, Switzerland), 9(10), 1501. https://www.mdpi.com/2304-8158/9/10/1501
[2] Ritter, J. C., & Budge, S. M. (2012). Key lipid oxidation products can be used to predict sensory quality of fish oils with different levels of EPA and DHA. Lipids, 47(12), 1169–1179. https://aocs.onlinelibrary.wiley.com/doi/10.1007/s11745-012-3733-7
[3] Phung, A. S., Bannenberg, G., Vigor, C., Reversat, G., Oger, C., Roumain, M., Galano, J. M., Durand, T., Muccioli, G. G., Ismail, A., & Wang, S. C. (2020). Chemical Compositional Changes in Over-Oxidized Fish Oils. Foods (Basel, Switzerland), 9(10), 1501. https://www.mdpi.com/2304-8158/9/10/1501
[4] Bannenberg, G., Mallon, C., Edwards, H., Yeadon, D., Yan, K., Johnson, H., & Ismail, A. (2017). Omega-3 Long-Chain Polyunsaturated Fatty Acid Content and Oxidation State of Fish Oil Supplements in New Zealand. Scientific reports, 7(1), 1488. https://www.nature.com/articles/s41598-017-01470-4
[5] Hands, J. M., Anderson, M. L., Cooperman, T., & Frame, L. A. (2024). A Multi-Year Rancidity Analysis of 72 Marine and Microalgal Oil Omega-3 Supplements. Journal of dietary supplements, 21(2), 195–206. https://www.tandfonline.com/doi/full/10.1080/19390211.2023.2252064
[6] Albert, B. B., Cameron-Smith, D., Hofman, P. L., & Cutfield, W. S. (2013). Oxidation of marine omega-3 supplements and human health. BioMed research international, 2013, 464921. https://www.hindawi.com/journals/bmri/2013/464921/
[7] Chevalier, L., Vachon, A., & Plourde, M. (2021). Pharmacokinetics of Supplemental Omega-3 Fatty Acids Esterified in Monoglycerides, Ethyl Esters, or Triglycerides in Adults in a Randomized Crossover Trial. The Journal of nutrition, 151(5), 1111–1118. https://www.sciencedirect.com/science/article/pii/S0022316622001444
[8] Tsai, C. C., Li, Y. C., Chang, L. C., Tey, S. L., Lin, K. J., & Huang, S. C. (2019). Long-Chain Fatty Acid Receptors Mediate Relaxation of the Porcine Lower Esophageal Sphincter. Frontiers in physiology, 10, 676. https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2019.00676/full
[9] Qin, J., Kurt, E., LBassi, T., Sa, L., & Xie, D. (2023). Biotechnological production of omega-3 fatty acids: current status and future perspectives. Frontiers in microbiology, 14, 1280296. https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1280296/full
[10] GOED Voluntary Monograph (2022). https://goedomega3.com/storage/app/media/Monograph/GOED%20Monograph%20-%202022%2001%2006%20-%20FINAL.pdf
[11] Cameron-Smith, D., Albert, B. B., & Cutfield, W. S. (2015). Fishing for answers: is oxidation of fish oil supplements a problem?. Journal of nutritional science, 4, e36. https://www.cambridge.org/core/journals/journal-of-nutritional-science/article/fishing-for-answers-is-oxidation-of-fish-oil-supplements-a-problem/EC656B7DAEF93BD39D043683CE8E20EA
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