Omega fish oils have long been a go-to health, beauty and wellness supplement. The oils are rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), and the benefits are seemingly endless—from improved mental health to better immunity, improved skin and hair, and reduced inflammation.
Why oxidation matters in fish oil supplements
However, these oils can also be vulnerable to oxidation if not created, packaged and stored carefully, which can affect the flavor and smell and compromise their nutritional value. Some people even argue that oxidized fish oil could potentially cause more health issues than it could solve.
Lorraine Perretta, head of nutrition at supplements brand Advanced Nutrition Programme, highlighted the risk of fish oil becoming rancid if products have not been correctly produced and packaged.
“When they are making the supplements, it’s possible for the oil to get exposed to oxygen and lead to oxidized fish oil,” she explained. “Some of the studies I’ve seen on this have been on products sold in markets like Australia, New Zealand and America.”
“The global organization for EPA and DHA (GOED) says that the oxidation ‘TOTOX’ score has to be below 26, but there are an estimated 30-40% of products on shelf that have levels above this figure,” she said.
Perretta expressed concerns that high levels of oxidation could in fact increase inflammation, which is essentially at odds with why someone would take a fish oil supplement. “Flavored fish oils, which are often given to children, can have especially high levels,” she added.
What the latest research says about rancid fish oil
Indeed, a 2023 study published in the Journal of Dietary Supplements, where researchers evaluated 72 of the most popular fish oil brands, found that 45% of them tested positive for being rancid. It also highlighted that many contained added flavoring that masked the rancid taste.
Various studies published over the past 10 years have disagreed on the potential health issues that oxidized fish oil supplements can cause, with some scientists finding health problems caused by rancid fish oil and others declaring that it is not a health hazard.
There has also been research into whether the production method of supplements can prevent this from happening. For example, one study undertaken by researchers from Istanbul Technical University and published in Food Science & Nutrition found that capsulated samples were better protected according to the sensory evaluation scores, since no rancid odor or flavor were detected in samples. The researchers said this indicated that the encapsulating material provided good protection against oxidation.
“While an increase in oxidation parameters was observed in different forms of fish oils with storage, it was observed that individual packaging had a protective effect against oxidation,” the researchers wrote.
Derek Tobin, business development and clinical science manager at Epax Norway, which produces high-quality fish oil for use in supplements, said he believed that the potential issues and side effects of rancid fish oil are poor taste and smell of oils and potential loss of effectiveness.
“I find no studies measuring efficacy as a function of oxidation, but there seems a general consensus that this could happen,” he said. “Fish oil is prone to oxidation, and this is most easily detected by consumers from a fishy smell, which sometimes can lead to fish burps or an upset stomach.”
However, as the earlier mentioned research in the Journal of Dietary Supplements found, often fish oil can be flavored, which can disguise this bad smell and taste.
Tobin pointed out that the European Food Safety Authority (EFSA) has performed a scientific evaluation of oil rancidity in fish oils from a safety perspective. The report is unable to set oxidation limits where toxicity might start but does state: “The refined fish oil production process typically includes several steps, which reduce the biological food safety risk to negligible”.
In Tobin’s view, there also a lack of research into potential toxic effects of rancid oil.
“Some studies can be misleading such as a report with a title implying loss of health benefits with oxidized fish oil, but the study looked solely at omega-6 derivatives,” he said. “Most omega-3 manufacturers by design have low levels of omega-6 in their products.”
Tobin said that GOED commissioned a safety review for use of EPA and DHA and found a lack of evidence to support oxidized lipid forms as disease/condition biomarkers [1].
He also pointed to a study that compared an omega-3 oil concentrate in a low and high oxidized form.
“To ensure oxidation, they bubbled oxygen through the oil at room temperature for 2x 20 minutes daily for 21 days,” he explained. “There were two interesting findings: First, the TOTOX (a measure of oxidation) was 45 (peroxide 18, anisidine 9), which though above industry cut-off levels (usually around 26), was lower than you might expect, suggesting oils are more robust than we might at first consider. Secondly, no increase in inflammatory markers, markers of oxidation or lipid peroxidation were seen in a human clinical trial after seven weeks of supplementation.”
In Tobin’s view, the findings of this study indicate that oxidized fish oil does not produce acute effects on inflammation.
The same research group performed a similar clinical trial with measurement of markers of vascular inflammation, he added. “Of particular note was the inclusion of oxidized LDL-cholesterol which is often found in atherosclerotic plaques. Again, no change in vascular biomarkers was seen with the ingestion of oxidized fish oil.”
Ellen Schutt, managing director at GOED, agreed the very low oxidation seen in EPA/DHA omega-3 products is not a safety issue and no studies have shown that it affects the efficacy. She added that good quality EPA/DHA omega-3 products do not have rancidity issues.
There is also confusion about flavored oils, which cannot be reliably tested for the secondary oxidation parameter (Anisidine Value), Schutt said.
“Therefore, it’s not a matter of flavored oils masking rancidity, it’s actually that the test does not exist to test these oils accurately for secondary oxidation,” she told NI. “Using it leads to inflated results that have characterized these oils as oxidized when that’s not the case.”
How manufacturers can ensure fish oil quality and safety
So how can omega supplement brands be sure that their supplements do not cause any potential issues?
Tobin drew attention to the fact that strict limits on fish oil quality are imposed by regulatory authorities and quality standard organizations (e.g., FCC, USP, PhEur) [2].
The main outcome of low oxidation, and indeed the focus of oxidation parameters in the industry, is to provide oils that lack any fishy smell or taste. This is achieved by removing oxidized oils and other impurities and by removing any contact of the oil with air. Epax, for example, uses nitrogen throughout the process of oil concentration and purification, has frequent testing of the oils and an optimized process to avoid exposure of the oil to air.
“When thinking oxidation, most people focus on anisidine and peroxide values, but there are also process-driven impurities which are controllable,” Tobin said. ”Many are regulated with maximum levels and again reputable manufacturers keep these to a limit."
He added that the levels of oxidation in fish oils from reputable manufacturers is very low and realistically the issue with fluctuations in these levels are considered as issues of smell and taste rather than inflammatory agents.
“Although it is difficult to quantitatively say when a fish oil will lose efficacy, or have any toxic/inflammatory effect, we can generally say that there is little evidence to support that these effects happen at oxidation levels commonly seen in products today,” he said.
Sources
1. Consulting, S., Hazard characterisation of the Long-Chain Polyunsaturated n-3 Fatty Acids DHA, EPA and DPA. 2012: Bethesda.
2. Nutrition, G.a.C.f.R., Oxidation in Omega-3 oils: An Overview.