More Information on DNA in Animal Products

Questions about the safety of transgenic DNA were originally asked in the mid-1970s, following the advent of recombinant DNA methodologies that utilized E.coli and recombinant plasmids. Maturin and Curtiss (1977) studied the intestinal fate and rate of degradation of E. coli and plasmid DNA in rats. The bacterial DNA in the small intestine degraded rapidly (initially 24 min-1) due primarily to secretion of pancreatic nucleases into the intestine and, secondarily by stomach acids. Plasmid DNA was even less stable, presumably due to its smaller size.

Both the World Heath Organization and the U.S. Food and Drug Administration concluded that there is no inherent risk in consuming DNA, including that derived from transgenic crops (WHO, 1991; US-FDA, 1992). The basis for their conclusion is that humans and other animals have always consumed DNA from a wide variety of sources including plants, animals, bacteria, parasites and viruses. DNA is an essential component of all living things, so it is present in nearly all foods humans consume, but in relatively small amounts. As mentioned above, the total amount of DNA in food contributes only 0.02% to the total dry matter of the food (Watson and Thompson, 1998). Foods derived from transgenic crops contain only 0.001% more DNA than traditional foods. To put this into perspective, a dairy cow eating transgenic corn would consume 6.8 µg/day of transgenic DNA out of a total ‘natural’ dietary DNA exposure of 680 mg/day.

Both transgenic DNA and DNA from non-transgenic crops are made of the same 4 nucleotides - adenosine, guanosine, thymidine, and cytosine. The addition of transgenic DNA does not add any new chemical entity, so the digestive system is well adapted to processing transgenic DNA. The specific sequence of nucleotides in a transgene that is responsible for the production of the novel protein is destroyed once the digestive process begins. Rasche (1998) conducted a direct analysis of the stability of transgenic DNA that encodes the PAT gene in canola. In this study the transgene was completely broken down into nucleotides in actual digestive fluids taken from pork, chicken, and cow within one hour at 37oC and pH 1.5. This rate of degradation is similar to other DNA molecules studied.

The gene sequence encoding a plant protein, whether non-transgenic or transgenic, is functional only when the DNA (gene) is activated in the plant cells; just the presence of the DNA alone in the diet is so common that it is of little consequence to the host.