Date Added to website 16th March 2014
As we all know, there are frequent arguments relating to the "scientific consensus" on the safety (or otherwise) of GMOs. Supporters of the GM industry claim that there are in excess of 2,000 studies demonstrating that GMOs are safe to eat, whereas GMO-Free USA has published a list of 1300 studies which they claim show that there are real risks associated with the consumption of GMOs. One side says their list is better than the other side's, or has more studies on it, or that its cited studies are "proper studies" from peer-reviewed journals, whereas the other lot includes items that are not pieces of original research at all. This all becomes rather sterile, and sometimes ends up in pantomime arguments on Twitter which say essentially "Oh yes they are!' or "Oh no they aren't!" ..... and so it goes on.
It is a very time-consuming business to go through long lists of articles in order to assess their "quality'" -- but one or two such efforts have been made. The most notable is the study by Domingo and Bordonaba in 2011: http://www.sciencedirect.com/science/article/pii/S0160412011000055
Those who have complained about sharp practice in the assembly of lists purporting to show "no harm" have frequently noted that large numbers of studies dressed up as GMO "safety assurance studies" are nothing of the sort, but are studies of "nutritional equivalence" designed to demonstrate commercial viability, with many such studies apparently specifically designed to show "no harm" -- through the use of a number of well-known laboratory protocol and "data manipulation" techniques.
So it was interesting to see this brief document from a researcher who prefers to remain anonymous, which describes the true nature of a list of 60 papers purporting to show that GMOs are safe to eat. There were 60 references on the list. But as we can see, after close scrutiny the list of relevant or valid papers was reduced to just three -- and the evidence if anything showed that the GM materials examined were actually harmful, rather than safe.........
The review was conducted in four steps by an independent researcher, on behalf of a government authority. Abstracts failing one step did not progress to the next. As each abstract needed to pass all steps, this approach provided a time-efficient means of culling unsuitable abstracts. There were 60 individual entries on the abstract list. However, one was not an abstract but an erratum, where the authors simply corrected errors in a table in a previously-written paper. Hence this was removed from the list, resulting in 59 actual abstracts.
Step 1. Was the paper published in a peer-reviewed scientific journal?
When considering scientific evidence, scientists view research that appears in peer-reviewed scientific journals as being of a higher standard than those that get published in other forms, generally because the quality of work has been properly reviewed in the former and not in the latter. Hence only papers in peer-reviewed scientific journals should be considered here. As abstracts rather than whole papers were provided, it was difficult to determine whether an abstract had come from a peer-reviewed scientific journal or not. However, there were four that were clearly from the "grey" literature. These were reports rather than scientific peer-reviewed papers. One of these abstracts was written entirely in German, but a translation of the "journal" title indicted that it was a technical periodical rather than a peer-reviewed scientific journal. All other abstracts were given "the benefit of the doubt" and passed this step.
Step 2. Are the studies relevant to human health?
Of the 55 abstracts that entered this step, 46 failed this step, being 78% of the original 59 references and 84% of the abstracts that entered this step. Most failed because they were animal production studies, ie they used diets or measured outcomes that were not applicable to humans.
• The effects of eating GM silage when humans do not eat silage.
• Diets were altered using ingredients that are not permissible in human diets eg sand and ground cardboard.
• Animal production outcomes were measured such as milk production, feed conversion to various types of carcass weight and even "sticky droppings".
• Animals with completely different physiologies to humans were used as experimental animals. For example, chickens were often used when they are clearly not comparable to humans – they have feathers, fly, lay eggs, do not suckle their young, have nucleated red blood cells, caeca, air sacks instead of lungs, kidneys that do not produce urine, two "stomachs", and swallow grit and pebbles to help grind their food – all of which would be considered highly unusual in a human. Studies on fish are even less comparable. Cows are also not comparable because, while they are at least mammals compared to many other animal models used in these studies, amongst other things, they have several stomachs, chew their cud, and can digest cellulose. Hence they can thrive on a diet that would kill a human; such as one consisting entirely of grass. Pigs are physiologically closer to humans and can be used in feeding studies designed to test human end points but in practice are rarely used due to their size. That is, they cost more to house and feed.
Other abstracts failed because they were not animal feeding studies at all, but measurements done in vitro or on soil or plants. Examples of the latter include comparisons of the composition of a GM crop to a non-GM crop and measurements of the amount of transgenic protein expressed in a GM plant.
Some studies looked at whether GM DNA could survive digestion and enter the animal's tissues, with some showing that it did and others that it did not. While the difference could be attributed to different digestion rates of different types of GM DNA, the studies also showed similar inconsistent results for non-GM DNA, indicating a problem with various detection methods in different hands. However, all but one were rejected as measures of human health because they used an animal model that was not comparable to humans (eg cows or chickens) or the outcome measured was not suitable for humans. Notably, a fairly famous study by Netherwood et al on humans, showing that GM DNA could be taken up by bacteria in the human gut, was not included in these abstracts.
Nine abstracts remained after this step, being 15% of the original abstracts in the abstract list and 16% of the abstracts that entered this step.
Step 3. Are these measurements properly and thoroughly measured?
To determine whether the measurements were properly and thoroughly measured requires looking at the details of the materials and methods used which are only available from the full paper, not the abstract.
Step 4. Are authors compromised by being too close to vested interests?
To date, a high proportion of studies on GM crops have been conducted by employees of GM crop companies or by people or institutions funded by these companies. Recent evidence from the medical literature has shown that published research funded by an industry body tends to be favourable to that industry body. In any final consideration of the veracity of evidence, it is therefore important to determine how close the authors are to GM crop companies. However, this cannot be determined from the abstracts. Some information should be obtainable from the acknowledgement section of the full paper. However, this has not always occurred with GM crop company-sponsored research.
Of the nine abstracts remaining at the end of this process, the majority (6 abstracts, 67%) showed potentially adverse effects of GM crops on the health of the experimental animals, while three (33%) found no adverse effects.
The six papers showing adverse effects found evidence that GM potatoes could harm the liver and gastrointestinal tract and that GM soy could adversely affect the liver and pancreas. One paper found that GM DNA from GM corn was detectable in the intestinal contents of pigs up to 48 hours after eating. This makes it available for uptake into tissues and gut bacteria.
Three papers found no adverse effects; on the development and function of mouse testes from eating GM corn, on some biochemical measurements from eating GM potatoes and on some pathology, haematology, biochemistry and urine measurements from eating GM soy.
This review was done on the abstracts in the abstract list as these are being used as stand-alone evidence that GM crops are safe to eat. At times, there was not enough information in the abstracts to determine if an abstract could pass step 1. However, all the abstracts that remained at the end of the next step (step 2) did indeed appear to have come from peer-reviewed scientific journals and hence passed step 1. These papers therefore passed both steps 1 and 2. There was not enough information in the abstracts to determine if a paper should pass steps 3 or 4. Full papers would need to be obtained to determine these matters. However, the author has previously read the full papers of four of the nine final abstracts. All of these papers showed potentially adverse effects and also passed steps 3 and 4. Therefore, a considerable proportion of the papers that show adverse effects from eating GM crops are indeed sound by these criteria. In contrast, some of the papers that show no adverse effects may, on closer scrutiny, show the authors to be too close to vested interests. In short, the list of abstracts cannot be used to support the view that GM crops are safe to eat. On the contrary, there is sound evidence in the list that GM crops may have adverse effects on human health.
How thorough and unbiased was the literature search used to produce the list of abstracts?
The list of abstracts did not contain many other animal production studies. However, these would have been culled in step 2 of this review. The list also did not contain some papers that would have passed all steps and which showed adverse health effects. The list also omitted findings in humans, including GM DNA from soy entering bacteria in the gut of humans and numerous papers on the serious adverse effects on people of eating tryptophan from GM bacteria as a dietary supplement. Furthermore, a literature search normally provides information about how the search was conducted such as the search engines that were used, the years searched and the terms that were used in the search engines. This was not reported for this review. Hence the professionalism and thoroughness of the literature review may be inadequate.
The list of abstracts does not support claims that GM crops are safe to eat. On the contrary, it provides evidence that GM crops may be harmful to health.