Triple stacked GM maize causes leaky stomachs

September 2018
Because partially digested food can be held in the stomach for some hours, the stomach is the part of our body most exposed to the materials in our diet. Yet, tests able to reveal pathological changes and gastric dysfunction, such as measurements of stomach tissue structure or diagnostic staining of stomach cells, are never included in GM safety assessments.

An Australian team of scientists has made a start on filling this gap.

Previously, a long-term GM feeding study on pigs (a good model for humans) revealed an increase in severe stomach inflammation in the test animals [1]. A follow-up study using rats (the accepted OECD* model for toxicological studies) has now been published, with equally disturbing findings.

The test rats were fed a GM triple-stacked corn containing two Bt insecticide genes and a glyphosate herbicide tolerance gene (the same three artificial genes that the pigs had been exposed to in the earlier experiment). The experiment ran for six months, double the standard time, to "better assess the effect of long-term consumption" of GM feed.

In this case, no inflammation of the stomach was observed. However, close examination revealed a high incidence of separation of the stomach cells. These cells should be held tightly together by a set of specialist proteins each with its own specific, protective function. This structure is vital to prevent the entry of, for example, viruses, bacteria and allergy-inducing proteins. In effect, the GM-fed rats had leaky stomachs.

A number of other, less pronounced, differences in the GM-fed rat stomachs were seen, such as elongated cells suggestive of a rapid repair of the stomach lining after damage, and abnormal cells which could be a precursor to cancer. Each of these changes on its own would probably not have clinical implications, but pooled to create an adverse events severity score, they showed a significant difference between GM-fed rats and non-GM-fed controls.

The authors were forced to make a number of departures from the 'ideal' experiment, resulting in interesting implications.

One arose from the need to adjust the rats' diet: the feed made specially for the experiment had to be reformulated after the start to increase its moisture content so as to optimise food intake.

Because the test GM feed was rectified before the non-GM control, the GM-fed rats ate more, were better nourished and grew bigger. This would be expected to reduce the observed differences between the (less well-fed) control rats and the (better-fed) test rats, and so understate the magnitude of any problems caused by the GM feed.

Secondly, the test feed was a stacked GM crop produced by breeding together three different GM crops. This meant that there was no such thing as a non-GM equivalent of the GM plants which could be grown alongside the GM crop to produce a scientifically valid non-GM control feed. The safety of such stacked crops is assumed by regulators on the basis that all three GM maize lines used to produce it have been individually declared 'substantially equivalent' to their non-GM counterpart.

Thirdly, so little uncontaminated maize is available in the USA that the Australian team had to use conventional maize grown in their own country for the control feed. As the authors point out, since the GM maize they used has been pronounced substantially equivalent to non-GM maize, no differences in feeding effects between the two should be present.


In light of the plethora of stacked-trait GM crops flowing into the market, the implications of the necessary deviations from standard protocol in this experiment are chilling: the production of non-GM control feed for a scientifically valid GM safety study is impossible, and even a compromise control crop grown on the same continent as the test crop is unobtainable. Further, it's clearly demonstrated that routine feeding studies have never been long enough, and that modern, varied, sophisticated analytical techniques to assess the safety of GM food are being by-passed.

This study makes it very clear that, although we have the technology for close examination of tissues and proper assessment of the clinical implications of GM in the diet, these are being side-stepped in favour of gross qualitative observations.

It's very difficult to measure safety parameters in any food because effects on the body can vary so enormously due to food combinations and the state of the consumer. We clearly need to adopt protocols based on adverse effects severity scores. Ask for these to be developed as a matter of urgency, because while the individual effects of GM food may not be clinically significant, if you have several types of malfunctioning tissue in your stomach, you might find yourself with a health problem. And if your health is already compromised in some other way, GM in your diet might be the last nail in your coffin.



*Organisation for Economic Cooperation and Development

  • Irena M. Zdziarski, et al., 2018, Histopathological Investigation of the Stomach of Rats Fed a 60% Genetically Modified Corn Diet, Food and Nutrition Sciences 9
  • Rats fed GM stacked-trait maize developed leaky stomachs, GM Watch 9.07.18

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