The concern with the production of novel proteins in food crops and food products by the unexpected CRISPR-NHEJ-indel process described in the new study is that it can result in altered plant biochemistry, leading to unexpected toxicity and/or allergenicity.
Numerous animal feeding studies (summarised in the book GMO Myths and Truths) show unexpected toxic or allergenic effects with the first generation of GM crops. There is every possibility that the second generation of GM crops – products of gene editing – will present similar problems. However, the necessary studies (including long-term animal feeding studies) have not been performed with gene-edited crops.
Commenting on the new study, London-based molecular geneticist Dr Michael Antoniou said, “The discoveries described in this study add to the increasing number of ways in which gene editing can go wrong. Regulators need to fully take on board these and other findings of off- and on-target unexpected outcomes from gene editing and subject all products produced with these methods to a comprehensive health risk assessment before considering market approval.” [Source]