Where does the GM go... after you've eaten it?

April 2011

What happens to the artificial DNA, novel proteins and by-products inside once they've been eaten?

After a New Zealand poultry producer claimed in advertising that its products contained “No ... GM ingredients”, the question was raised: do products made from chickens given a 13% GM soya diet really have “no GM content”?

Canterbury University's Professor of Genetics and Molecular Biology, Jack Heinemann, was engaged by the New Zealand Commerce Commission to to investigate and comment. His remit was to include:

• The transfer of DNA from GM plants into animals
• The transfer of GM proteins into animals
• The ability of GM feed to alter the metabolites in the animal product
• The ability of GM feed to cause physiological or immunological responses in the animal
• The presence of GM ingredients incorporated into the final animal product.

Specifically, he was not asked to evaluate food safety claims, biological significance, nor animal welfare issues.

Professor Heinemann found “substantial and credible literature” which detected DNA and proteins unique to GM plants within animals and animal products. The possible sources of such GM material were identified as coming, not only from feed, but from proximity to other animals fed GM, and from subsequent processing. He found:

“compelling evidence that animals provided with feed containing GM ingredients can react in a way that is unique to an exposure to GM plants. This is revealed through metabolic, physiological or immunological responses in exposed animals ... The cumulative strength of the positive detections reviewed ... leave me no reasonable uncertainty that GM plant material can transfer to animals exposed to GM feed in their diets or environments, and that there can be a residual difference in animals or animal-products as a result of exposure to GM feed.”

The overview of the study stressed that the focus of the investigation was on the parameters described above. In regard to the total citations on GM-fed animals, Prof. Heinemann noted “There is a moderately larger pool of published studies that report no effect of GM feed on animals.” However, regarding the much smaller number of studies which looked specifically at the parameters of interest, he emphasised that “the number of research studies that report no detection of physiological, immunological or metabolic effects, or absence of DNA or protein, is about the same as the number that report detection. In the relatively small literature which measures these particular parameters, there is a large proportion that reports significantly different effects of GM and conventional feed on animals or the presence in animals of DNA and protein unique to GM plants.”

(COMMENT Does this last indicate how easy it is for 'science' to find only what it's looking for, and so bury bad news?)

It's interesting to view Prof. Heinemann's evidence from the stand-point of animals, such a pigs and rodents, which are used as models for human nutritional studies. In these, it's clear that some DNA and protein certainly survive digestion.

In pigs fed 63% GM maize, identifiable engineered DNA was detected in all areas of the gastro-intestinal tract, and in one study GM maize DNA, but not conventional DNA, was found in the pigs' blood. Identifiable GM protein fragments in the order of half the size of the original protein were detected in all areas of the gut.

Similarly, GM-fed rats were found to maintain a transgene in multiple copies throughout the gastro-intestinal tract, while the evidence on GM proteins was variable. A number of immunological responses have been observed in rats fed Bt proteins and lectins (both favourite constructs for genetic engineering). One study on GM rice found antibodies against a Bt-toxin and lectin in the control (non-GM-fed) animals which had been housed in the same facility as the test (GM-fed) animals. The authors commented:

“As the nasal and bronchial mucosal sites are potent sites for induction of an immune response, the results may be explained by inhalation of particles from the powder-like non-pelleted diet containing (lectin or Bt) toxin, thereby inducing an (anti-lectin and anti-Bt) response ... These results support our assumption that the induction of the ... antibody response in the control groups occurred after inhalation.”

Physiological effects of GM-chow in rats and mice include pancreatic malfunction and signs of cellular responses to toxins in the liver and male reproductive system, and immune reactions in the gut. 

Lots more questions arise from that first question on the chicken with “No GM content”. For example, engineered DNA routinely includes sections from pathogenic viruses and bacteria. If these don't get digested, where do they end up?

Protein fragments which resist digestion can stimulate immune-system responses which can generate cross-reactivity, especially to other (non-GM) proteins present in the same meal. Global immune-reactions to staples such as rice and maize would not do the people of the developing or developed worlds any favours.

Just think what could happen inside YOU after a meal (hypothetical in Europe, reality in America) with multiple versions of engineered DNA and protein in it?

As Arpad Pusztai said “whatever our animals eat, we shall also get back indirectly”.

(This article is adapted from an article which first appeared on GM-free Scotland in December 2009. The article is archived here.)

SOURCES

• Jack Heinemann, Report on animals exposed to GM ingredients in animal feed, Report prepared for the Commerce Commission of New Zealand, 24 July 2009
• Inghams warned over GM free chicken claims, Commerce Commission (NZ) Release No. 50, 18.11.09
• Letter from Arpad Pusztai to GM Watch on the 10th anniversary of his television interview on the effect of GM potatoes on rats, 10th August 1998, www.spinprofiles.org/index.php/Arpad_Pusztai