EU approvals: new evidence showing Bt toxins cause side effects

EU Commission calls on EFSA to re-evaluate several genetically engineered crops

22. December 2022

22 December 2022 / New publications indicate that so-called Bt toxins have previously unknown side effects. Bt toxins are produced as insecticides by many currently cultivated transgenic plants. More than 50 of these plants may also be imported into the EU and processed into food and feed. The toxins are supposed to be harmful only to certain pests and cause no side effects. However, current findings have cast considerable doubt on these assumptions. Testbiotech has already drawn the EU Commission’s attention to this in recent statements on EU approvals. In one case, the Commission has already responded and asked the European Food Safety Authority (EFSA) to carry out a re-evaluation. EFSA has now submitted a list of questions to Syngenta and other companies.

This case involves Syngenta’s genetically engineered (GE) maize, MIR162, which expresses a specific Bt toxin (Vip3). A patent recently granted to Syngenta (EP 3632202 B1) shows that GE maize expressing Vip3 toxins can have unexpected side effects. The patent claims genetically engineered plants that exhibit reduced male fertility, which makes them particularly suitable for hybrid breeding. The background to this unexpected effect and also possible further effects on plant metabolism remain unclear and have not yet been examined in the context of authorisation procedures.

The European Food Safety Authority (EFSA) only recently once more declared MIR162 to be safe. Although Syngenta’s patent application was already available at that time, the Chinese-Swiss company did not report the safety-relevant data to EFSA. Following a tip-off from Testbiotech, the EU Commission has now called on EFSA to re-examine the safety of all genetically modified plants expressing Vip3 that have been authorised in the EU. Eight approvals in total are affected.

The safety of another type of Bt toxin, known as Cry1A, also appears questionable following new findings. Cry1A is found, for example, in the only genetically engineered crop approved for cultivation in the EU, i.e. maize MON 810, produced by Monsanto (now Bayer). According to a government-funded study carried out by French researchers, which has not yet been officially published, Cry1A is suspected of harming “non-target organisms” via a hitherto unknown mechanism. Some investigations were carried out with fruit flies (Drosophila), which are considered important model organisms. Although fruit flies should not be sensitive to the toxins, it was in fact shown that ingestion of the toxins can trigger the death of intestinal cells. As a result, there is a disruption in the formation of new cells: instead of ‘normal’ intestinal cells, hormone-forming (enteroendocrine) cells now grow in greater numbers. These cells are involved in the regulation of many physiological functions, such as feeding behaviour, metabolism and immune response, in both humans and animals.

According to the scientists, the functionality and hormonal activity of the intestine could also be disturbed by Cry1A toxins in other species, as the described mechanism in the formation of new intestinal cells is the same in all animal species. According to the authors, there is therefore a need for further research, which should also take genetically engineered Bt plants into consideration.

In its risk assessment of Bt toxins, EFSA has so far assumed that they cannot be effective in the gastrointestinal tract of mammals because, unlike the intestines of certain insect species, they have no receptors with high specificity for these proteins. The agency ignores the fact that there are other mechanisms and processes that make Bt toxins biologically active in so-called “non-target” organisms, which could also lead to adverse effects on health. There is also evidence that the toxicity of the toxins produced by the plants is much higher than that originally found in nature. Testbiotech is demanding that the EU Commission take the new findings as an opportunity to thoroughly review previous assumptions regarding the safety of Bt plants.

Christoph Then, Tel +49 151 54638040,

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