Concerns are sometimes expressed that the presence of recombinant DNA in GM foods may pose health risks to people consuming the food. This has been an active area of research for nearly twenty years and the overwhelming scientific consensus from those studies is that the presence of recombinant DNA in food does not pose any human health or safety concerns.
What is recombinant DNA?
Recombinant DNA is the term used to refer to the new DNA that is formed by splicing together pieces of DNA from different organisms or cells. For example, a DNA sequence or gene from bacteria may be recombined with DNA sequences from a plant to produce a new recombinant DNA which can then be transferred to a plant to give it a new characteristic previously only found in bacteria – e.g. herbicide resistance.
Should I be concerned about recombinant DNA in my food?
No. DNA has always been present in food, and recombinant DNA is chemically no different to other DNA (non-recombinant DNA) found in food.
Genetic modification using recombinant DNA techniques results in the reassortment of DNA sequences but leaves chemical structure unchanged. Recombinant DNA is therefore chemically identical to non-recombinant DNA. There is also very little that is unique about the sequences of recombinant DNA, as most recombinant DNA sequences are derived from naturally occurring DNA sequences. Many of these naturally occurring DNA sequences are already present in the food we eat, either because they are derived from plant genes, or from bacteria or plant viruses that are often found naturally associated with many fresh foods.
How much DNA is normally found in food?
The total amount of DNA in food varies according to the type of food. For example, edible offal and animal muscle tissue contain high levels of DNA, whereas plant foods such as grains or potatoes contain less DNA because they generally have less cell nuclei than offal and muscle tissue. How much DNA is consumed by people on a daily basis is therefore heavily influenced by a person’s diet. One estimate however has put the amount of DNA consumed on a daily basis in the range of 0.1 to 1.0 gram per person per day. The presence of recombinant DNA in food does not increase the overall dietary intake of DNA because it represents only a tiny proportion of the total DNA found in food.
What happens to DNA in food when it is processed and/or eaten?
Food processing may lead to partial or complete degradation or removal of DNA. The type of processing used will determine how much DNA is broken down and removed. For example, the purification of sugar and the production of refined oils will remove most, if not all, DNA, whereas heating/cooking may cause DNA to be fragmented without reducing the total DNA content.
The fate of ingested DNA has been thoroughly studied. DNA is extensively broken down during digestion and this process is the same for recombinant DNA and non-recombinant DNA. Some studies have shown that not all ingested DNA is completely degraded. Some DNA fragments may remain which can be detected in the digestive tract, and which have also been shown to pass into the bloodstream and other body tissues. This is a normal biological phenonemon that can be expected to occur with both non-recombinant and recombinant DNA and there is no evidence that this represents a human health or safety concern. The cells of the human body have effective mechanisms of defence against the uptake, integration and continued expression of foreign DNA from food or from the environment.
Can ingested recombinant DNA be transferred to microorganisms in the digestive tract?
It is theoretically possible that transfer may occur, just as it is also possible that ingested non-recombinant DNA may also be transferred. However the likelihood is considered by scientists to be extremely low and it is also highly unlikely that any transferred DNA would be successfully maintained by the microorganism.
The transfer of recombinant DNA into gut microorganisms has been the subject of intense scientific scrutiny and debate, particularly in relation to the use of antibiotic resistance genes, and the possibility that such transfer could compromise the therapeutic use of antibiotics. While microorganisms possess sophisticated systems for DNA uptake from their environment, the overwhelming scientific consensus is that the likelihood of successful transfer and functional maintenance of recombinant DNA by gut microorganisms would be extremely low.
How does FSANZ consider this issue in the GM food safety assessment?
The main objective of a GM food safety assessment is to identify whether new or altered hazards are present in the food as a result of the genetic modification, and if present to determine what risk, if any, they may pose to human health.
The key issue therefore is whether the occurrence of recombinant DNA in food poses any greater risk to human health, than that posed by the significantly larger amount of non-recombinant DNA already present in food. In general, FSANZ considers the risk to be equivalent between recombinant and non-recombinant DNA.
The recombinant DNA sequences that are used to produce GM foods are fully characterised by FSANZ during the safety assessment. Any recombinant DNA sequences which may raise safety concerns if ingested will be identified during that process.