5.1—DNA fragments in the gut are plentiful, but cause no problems
Ingested food contains vast numbers of genes which are digested and fragmented as they pass through the digestive canal, and transgenic DNA is a minute fraction of this traffic.
Analysis of Peer-Reviewed Research:
The fact that fragments of ingested DNA can survive for a limited time in the intestinal tract and are taken up by the body is being used by Jeffrey Smith to argue the possibility of gene transfer from GM foods to either internal organs or intestinal bacteria. This concern is based on an erroneous concept that DNA and genes are synonymous. A short fragment of DNA is not a functional gene, and there are no known instances of genes being transferred from food, transgenic or conventional, to either gut bacteria or to tissues or organs. Ingested DNA is rapidly degraded by various digestive enzymes, first to small DNA fragments of various sizes and subsequently down to nitrogenous-sugar building blocks of DNA. DNA-fragments can be taken up by the body or intestinal bacteria, but these fragments are not functional genes any more than a few letters can be said to form a meaningful sentence. There is no difference between the small amount of extra DNA inserted in the plant by genetic engineering and the large amount of existing plant DNA which it is added to in this respect.
Thus humans have always been exposed to DNA fragments in their guts. No harmful effects have been identified and there is no evidence for this DNA affecting germ cells.
1. Scientific investigations mentioned by Genetic Roulette do not detect genes, they detect gene fragments that are unable to function as genes. A fragment of a gene cannot confer the characteristics of the complete gene and its associated traits. Without a functioning promoter a protein cannot be formed. A fragment of a gene cannot confer ability to produce the complete protein associated with the full gene. Smith interchanges the words genes and DNA to make it appear that whole genes are being ingested. The human diet is full of gene-sized fragments of DNA but eating these genes and gene fragments has never harmed us because we have evolved to survive the every-day challenges of eating food.
2. Smith misleads readers about survival of full-length transgenes in the gut of human volunteers. Smith mistakenly claims that a human feeding study detected the survival of full-length transgenes in the gut. Measurement of a small fragment of the full gene (Martin-Orue and others 2002, Netherwood and others 2004) does not show this. Smith is simply misrepresenting what the scientific article says.
3. No fully working transgene has been detected as moving in the way Smith asserts. There are no reports available in the scientific peer reviewed literature demonstrating that a working gene has transferred from transgenic plants (Hohlweg and Doerfler 2001, Thomson 2001). Most worryingly (see Smith’s sections 5.4 and 5.6) Genetic Roulette fabricates such evidence.
4. Food contains a massive numbers of other genes than the transgene and always has contained much DNA. The scenarios of gene fragment movement outlined in Genetic Roulette also apply to other food DNA, and are part and parcel of humans eating food. Over millions of years, the human gut of our ancestors has been exposed to undigested gene fragments without them causing any identifiable harm. Smith fails to discuss the similar risks posed by non-transgenic plant DNA which is abundant in the gut and which is taken up in the spleen and liver (Hohlweg and Doerfler 2001) . He pays no attention to existing sources of DNA hazards in conventional food and the evidence available from their history of safe use (Beever and Kemp 2000, Carver and Walker 1995, Hohlweg and Doerfler 2001, Doerfler and others 2001, van den Eede and others 2004).
Beever D and Kemp C (2000). Safety issues associated with the DNA in animal feed derived from genetically modified crops. A review of scientific and regulatory procedures. Nutritional Abstract Reviews Series B: Livestock Feeds and Feeding 70:175–182.
Carver J and Walker WA (1995). The role of nucleotides in human nutrition. The Journal of Nutritional Biochemistry 6: 58-72. Information on RNA, DNA in food and its digestion.
Doerfler W, Hohlweg U, Mueller K, Remus R, Heller H and Hertx J (2001). Review: Foreign DNA integration–perturbations of the genome–oncogenesis. Ann N Y Acad Sci. 945:276-88.
Hohlweg U and Doerfler W (2001). On the fate of plant or other foreign genes upon the uptake in food or after intramuscular injection in mice. Mol Genet Genomics. 265(2):225-33. Non-transgenic plant DNA persists in the gut. Fragments are taken up into the spleen and liver of the animals that eat it. But there is no evidence for the expression of genes that were taken up in the diet. Tests for appearance of this DNA in progeny over eight generations were uniformly negative. The conclusion is that DNA does not get into the germ line
Netherwood T, Martín-Orúe SM, O’Donnell AG, Gockling S, Graham J, Mathers JC and Gilbert HJ (2004). Assessing the survival of transgenic plant DNA in the human gastrointestinal tract. Nature Biotechnology 22(2):204-209. Studies on the movements of gene fragments from food digestion in the gut of human volunteers.
Thomson J (2001). Horizontal transfer of DNA from GM crops to bacteria and to mammalian cells. Journal of Food Science 66(2), 188-193.
van den Eede G, Aarts H, Buh H-J, Corthier G, Flint HJ, Hammes W,
Jacobsen B, Midtvedt T, van der Vossen J, von Wright A, Wackernagel W and
Wilcks A. van den Eede G and others (2004). The relevance of gene transfer to the safety of food and feed derived from genetically modified (GM) plants. Food and Chemical Toxicology 42:1127–1156
In spite of industry claims, transgenes survive the digestive system and can wander.
1. Industry advocates claimed that genes were destroyed during the digestion of food and therefore gene transfer to gut bacteria or organs was extremely unlikely.
2. Studies now verify the genes can survive digestion, both in humans and animals.
3. Animal studies on non-GM DNA also verified that it can pass through the placenta into the features, from the digestive channels into the blood and organs, and even penetrate the blood brain barrier.
Genetic Roulette discusses how sensitive tests can detect fragments of genes from digested food away from their original locations.