In fact, consumers could be at substantial risk from genetically engineered foods. In nature, crossbreeding only takes place between very closely related species. Any genetic changes occur very gradually, over time. But genetic engineering allows the joining and transfer of genes between totally unrelated organisms. EMS was linked to the consumption of a dietary supplement called L-tryptophan .
Genetic engineering can also introduce known and unknown allergens into common foods.
For example, Pioneer Hi-Bred International injected normal soya beans with genes from Brazil nuts to increase their protein content. The desired result was achieved, but the new 'improved' beans were never approved for sale. Nobody knows what allergic reactions people might have to them. Genetically engineered foods could also spread resistance to antibiotics in animals and human populations, thus undermining their effectiveness in treating diseases. When geneticists inject foreign genes into plant or animal cells, they often link them to other genes, called 'trackers'.