A new study funded by the Global Organization for EPA ad DHA omega-3s (GOED) examines potential fish oil oxidation following earlier findings that raised toxicity concerns, Nutra Ingredients reported on 2 November.

Published in Foods, the new study was carried out in response to a 2016 paper published in the American Journal of Physiology that used a highly rancid oil from the livers of hoki, a cod-like fish that is also known as blue grenadier or blue hake.

The species is the basis of a commercial fishery in New Zealand.

The 2016 study had found that when the oil was fed to pregnant rats, it had caused them to abort their unborn pups, Nutra Ingredients reported.

At the time, the study had been criticised for using a test material that did not represent any oil available on the market sold as a dietary ingredient.

The test material had been prepared by bubbling oxygen through the hoki liver oil for 30 days under fluorescent lights at room temperature.

In addition, the researchers had used oil that contained no antioxidants to prevent spoilage, which is a standard manufacturing practice in the dietary supplement industry.

Authors of the new study included Gerard Bannenberg, director of compliance and scientific outreach for GOED and Adam Ismail of KD Pharma, who is the former executive director of GOED. Experts from the University of California Davis, the University of Montpellier, in France, and the Université Catholique de Louvain, in Brussels, were also involved.

The aim of the GOED study was to compare the process of oxidation between a hoki liver oil and an anchovy oil, which represents the majority of fish oil omega-3s products on the market.

For both oils, the researchers strove to replicate the extreme oxidation conditions of the 2016 study.

The authors said that the use of a different type of oxidation condition, along with the inclusion of a more commonly used and antioxidant-stabilised refined anchovy oil, had demonstrated that different oils contained and developed distinct patterns of oxidation products and that the presence of added antioxidants markedly delayed oxidation.

“It is important to emphasise that under production and retail conditions, 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.

In the earlier study, very high doses had been given to pregnant rats which, when scaled to human adults, would consist of a daily dose of 45ml of fish oil, Bannenberg told Nutra Ingredients.

“That is at roughly 10 to 100 times what a person would take in the form of a dietary supplement,” he said.

Many studies of fish oils available in the USA, the UK, Australia and elsewhere had shown that these oils had generally shown good quality from an oxidation perspective, he added.

“While taking such oils to an extreme oxidation condition in the laboratory might raise some valid questions for further research, it does not raise any sort of alarm for consumers,” he said.

“The risk that consumers might buy a dietary supplement containing a rancid oil, if that means a severely oxidised product, is very small if not absent.”