A Study on Studies that Report Adverse Effects of Transgenic Food & Feed

Our policy at the Legume Laboratory is to report on the latest science surrounding the way we feed ourselves and possible methods of feeding a growing population in a world of limited resources and escalating environmental pressures.

Although we have a keen interest in the public discourse surrounding genetically modified crops, delving into popular arguments against their use falls foul of the line we have drawn in the sand for what we will report on.

However, an article in the Plant Biotechnology Journal reviewed a number of studies that are usually cited by proponents of the anti-GMO movement as evidence of the adverse health effects of these crops. Although this is usually one tenet of a larger argument against the use of genetically modified food, the use of published scientific papers to support part of the argument opens it up the rigors of scientific critique. This review gave us the ability to write about the subject.

Which papers were reviewed?

Before deciding which papers were to be reviewed, the authors of the review point out the noticeable foible whenever reading a commentary on genetically modified crops – that the only commonality between the variety of “GMO” foods is the process of creating them. Although transgenic crops may be created by the same process, the type of modification made or the trait inserted into the crop are individually known as ‘events’. The paper reports that while the FDA has reviewed 153 individual events, the majority of studies that report negative effects and are the focus of negative commentary relate to relatively few events. Although the studies reporting adverse effects are highly publicised, studies reporting no safety concerns garner little public attention.

In selecting articles for review, the researchers took the citations listed in four review papers which concluded that there are negative effects related to transgenic agriculture (Domingo and Bordonaba (2011); Dona and Arvanitoyannis (2009); Magana-Gomez and de la Barca (2009) and Seralini (2011)) plus those cited by the organisations ‘GM Free USA’, ‘Coalition for a GM Free India’ and ‘GM Watch’. Of these, studies not published in scientific journals or which didn’t evaluate whole food/crops but only pure proteins were excluded.

The result was 35 studies which met the criteria. The authors make a number of observations about the selected studies, including that:

  • they make up fewer than 5% of the total number of studies assessing the safety of transgenic crops;
  • nearly half (43%) of the studies looked at a herbicide resistant soy bean the product of one particular transgenic event;
  • 23% of the studies focused on another single event, an insect-resistant maize;
  • 9% studied crops not commercially available;
  • 20% of the studies did not indicate which transgenic event was being evaluated;
  • 31% of papers were authored by the Malatesta group at two particular Italian universities;
  • Only one article was published in a high ranking journal – (Ewen & Pusztai (1999)). The article was published with an analysis written by the editors which elucidated several significant criticisms of the study. The editors also commented that by publishing the article they did endorse the study or its conclusion but instead thought that there was a public interest in publishing it so that it could be evaluated by other scientists and to avoid cries of suppression from scientists claiming the existence of these negative effects.

Conflicts of interest

We start this section by first pointing out that the authors of this paper declare their own conflict of interest, noting that the lead author is from a lab which obtains funding from GM developing companies, while the second author has performed publicly-funded research into transgenic crops.

All of the 35 papers they studied however contained no declarations of conflict. Further analysis by these researchers revealed that half of the papers did not provide any information on where funding for the research was obtained while 40% of the papers showed no conflict of interest due either to funding sources or personal affiliations of the authors to groups known to have particular positions on transgenic agriculture.

What about the quality of the studies?

In order to assess the quality of the studies the researchers critically analysed the studies using a standard used by a number of authorities and outlined in a number of papers to assess the safety of the transgenic food. The criteria included:

  1. Control and experimental varieties should be from matching or very similar genotypes, be grown in the same fields, under the same conditions and in the same seasons to avoid confounding factors affecting the results;
  2. Statistical tests should be chosen before the study is performed, avoiding tests being chosen or changed throughout the experiment to obtain a desired result; and
  3. If results show some difference between the transgenic and control crops, the study should be contrasted with similar previous studies that obtained different results and a hypothesis put forward as why there is a discrepancy between results.

In finding that all of the papers failed to meet one or more the criteria the researchers point out problems with each of the studies, some of the bigger issues being:

  • Three of the papers did not perform any experiment and instead analysed preexisting data with different statistical methods to find significant differences between the study and control groups where the original paper did not. Two of these papers managed to find significant effects at low doses but at higher doses the effect was not seen, contrary to the dose-response reaction normally seen in toxicology studies;
  • Ayyadurai and Deonikar (2015) predicted increased formaldehyde and decreased glutathione in GM soya bean crops based on reviewing data from 6,000 studies without specifying the data used and without validating the prediction experimentally;
  • A series of studies by the Malatesta group contained multiple flaws, particularly that levels of isoflavones, which themselves can have a physiological effect on mammals, weren’t measured between transgenic and control crops, adding an uncontrolled confounding variable into the studies;
  • Of four studies emanating from Professor Infascelli’s group, two  were investigated, retracted and the authors reprimanded for digitally manipulating images used in the papers which found GM feed detectable in goats;
  • Finamore et al. (2008) studied the ingestion of maize in mice, finding that it caused an immune response. However, they dismissed the effects of mycotoxins on the immune system stating that they were at acceptable levels when in reality they were twice as much as allowed;
  • Trabalza-Marinucci et al. (2008) don’t advise the variety of maize used in the study nor mention mycotoxin effects while Magana-Gomex et al. (2008) have a similar problem, not specifying whether genetically similar soya beans of similar origins were used;
  • Seralini et al. (2014), a republished article of one previously retracted in 2012, reported elevated tumour and mortality rates in rats. The paper was heavily criticised for such reasons as:
    • the reported tumour rate is within the normal range for the species of rat experimented with;
    • the data was statistically analysed in multiple ways and, when corrected for multiple comparisons by scientists reviewing the study, the results obtained by the authors disappear;
    • the 10 rats used was too small a sample size for the type of study;
    • a dose-response relationship wasn’t observed;
    • the results section contained pictures of treated rats with huge tumours but no pictures were included of the control rates;
    • the results conflict with previous studies.
  • Fares and El-Sayed (1998) concluded that potatoes with added Bt protein – added as a crude extract without analysis of the crudeness of the extract – caused adverse effects.
  • Some examples cited do not show any adverse effect, contrary to how they are reported in the reviews and websites that they are cited in.

In contrast to the small set of error-prone reports which conclude that there is a link between genetically modified food and adverse health effects, there are somewhere around 473 papers that do not have the same quality problems. These papers cover a significantly greater number of transgenic events. Throughout all of these studies, there have been no unfavourable or concerning findings made about adverse health effects.


The weight of rigorously obtained evidence is firmly supportive of the safety of transgenic crops. Although safety concerns should always be investigated, given the weight of evidence in support of the safety of transgenic


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