Persistence of transgenic DNA in processed foods of animal origin: a potential biological risk.

The consumer awareness on the use of genetically modified organisms (GMOs) in food production is growing rapidly, as well as the demand for total transparency. The authorization of GMOs raw materials for further processing into animal feed or food is subject to strict European standards, and the labeling of their presence just above 0.9% is mandatory. But there is no obligation to inform the consumer about their use in the production process. It follows that the consumer may be informed of the presence of GMOs in food only when it exceeds the threshold value of 0.9%, while being completely unaware if animal products were obtained by feeding the animals with even 100% GMOs. Processed foods have gained popularity in recent years, many of the most produced being of animal origin, such as dairy products, meat and fish. One of the most studied GM food safety concern is the fate of ingested recombinant DNA throughout the food chain, from GM crops through the gastrointestinal tract (GIT) of livestock, then to animal tissues and offspring and subsequently to humans. The main biological risk is the occurrence of horizontal transgenic transfer (HGT) to bacteria in the host GIT or animal cells, with many, almost unexplored implications. The goal of this review is to organize and summarize the significant amount of research regarding the fate of dietary DNA in livestock and its persistence in animal origin processed food. The main technique of investigation is Polymerase Chain Reaction (PCR). Many results of recent publications agree that most of the DNA is degraded in the GIT by endogenous restriction nucleases, nevertheless some DNA fragments have been found in animal tissues and in products such as milk and meat. Many discordant results have been reported about the presence of transgenic DNA, due to methodological limitations. Therefore additional research is needed in the field of both genetic traceability studies and DNA quantification methods development.