Formulators working with fish oil should have comprehensive knowledge of oxidation and its effects on the specific omega-3 product being produced. A recent study demonstrated that plenty of variables are at play that affect quality and safety.
 
In a recent analysis published by the Global Organization for EPA and DHA Omega-3s (GOED) in the journal Foods, researchers analyzed the chemical composition of fish oil after exposure to varied oxidative conditions.
 
Omega-3s of all kinds are prone to oxidative degradation. Without appropriate preventive measures, oxidation can cause fish oil products to exceed voluntary safety recommendations.
 
Additionally, a number of academic publications have claimed that fish oil supplements were mostly oxidized, did not contain the claimed amount of EPA or DHA, and could be associated with negative health consequences.
 
To reach an understanding about the changes to fish oil’s chemical composition over time, several collaborating GOED members teamed up with academic researcher from Belgium, France, and the University of California, Davis.
 
The study is part of GOED’s Oxidation Plan, which involves a number of clinical trials intended to address oxidation-related complaints, such as that oxidation reduces EPA/DHA levels and could create a number of harmful compounds, among other complaints.
 
Previous Research
The GOED study was carried out in response to a previously-published study which appeared in the American Journal of Physiology in 2016 called “Oxidized fish oil in rat pregnancy causes high newborn mortality and increases maternal insulin resistance.”
 
During that study, pregnant rats were administered 1 ml of either unoxidized or highly oxidized hoki liver oil, or a placebo until birth. Maternal intake of oxidized fish oil significantly increased insulin resistance at the time of weaning compared to control and placebo, and the oxidized fish oil group also had significantly higher rates of infant mortality at day 2. The oxidized fish oil in the study was treated for 30 days by bubbling oxygen under a fluorescent lamp at room temperature, causing it to be characterized by a high concentration of lipid peroxides, which the authors believed could have been associated with oxidative stress (which is known to have adverse effects on a number of conditions related to pregnancy). The fish oil was not treated with antioxidants, and no co-administration of antioxidants occurred during this trial.  
 
A Second Look
According to the more recent publication to which GOED contributed, the adverse effect on pregnant rats caused by highly rancid hoki liver oil used in the 2016 was attributed to lipid hydroperoxides which formed during the experimental conditions to which the oil was exposed to. Other chemical changes that the authors hypothesized could have been present in the oxidized hoki liver oil at the time were not discussed.
 
The more recent trial replicated the conditions by which the hoki liver oil was oxidized in the previous study, and exposed anchovy oil to similar conditions, as anchovies are a common source of commercially available fish oil products.
 
Additionally, the study analyzed the effects of a less extreme oxidation method, which involved exposing fish oil to air contact in the dark, which is an oxidation condition “more relevant to retail products,” the authors said. It was determined that anchovy oil had a different chemical oxidation signature to hoki liver oil, due primarily to the fact that each contained a different profile of antioxidants, and that the applied oxidative conditions caused significant differences.
 
Study authors said the highly rancid hoki liver oil, which was intended to replicate the oil analyzed in the 2016 study, contained potentially harmful chemicals that may have been overlooked, and that the infant mortality and insulin resistance seen in pregnant rats may have been attributed to lipid hydroperoxides while isoprostanoids and oxysterols were overlooked.
 
“Quality guidelines for edible oils set by regulatory authorities exist to avoid rancid products entering the market,” the authors of the study said. “Producers of oils and retailers have also set voluntary quality limits through organizations such as [GOED]. Industry guidelines assist in making sure products comply with the applicable quality limits set by regulatory agencies for the markets where products are sold […] Recent studies show that the large majority of ingredient oils as well as finished products found in retail stores is of acceptable quality, although further improvements in oxidative quality can be made for some retail products.”
 
Further, the authors discussed other studies providing evidence that consuming mildly oxidized fish oils, rather than oils which are extremely rancid, does not significantly alter biochemical parameters in the body.
 
“The temporal analysis of chemical compositional changes of minimally refined antioxidant-free hoki liver oil under harsh oxidative conditions has confirmed the marked over-oxidation of the oil,” the authors of the study concluded. “Extension of the study to a different type of oxidation condition, as well as including a more commonly used and antioxidant-stabilized refined anchovy oil, demonstrated that different oils contain and develop distinct patterns of oxidation products, and that the presence of added antioxidants markedly delays oxidation.”
 
The authors also concluded that other oxidation products besides fatty acid peroxides should be considered to understand how oxidation effects any fish oil product, such as those derived from oil components including other fatty acids and lipids. A conclusion cannot be drawn for all fish oil ingredients based on the results of one oxidated fish oil or product, they said.
 
Additionally, “fish oils and other EPA/DHA omega-3 products would never be exposed to the harshness of the employed experimental oxidation conditions in this study,” the authors said. Beyond refinement and added antioxidants, encapsulation and packaging provides another parameter of oxidation resistance in omega-3 products.