Genetically modified foods and the Pusztai affair

BMJ 1999; 318 doi: https://doi.org/10.1136/bmj.318.7193.1284 (Published 08 May 1999) Cite this as: BMJ 1999;318:1284
  1. Jonathan M Rhodes (rhodesjm{at}liverpool.ac.uk), Professor of medicine
  1. University of Liverpool, Liverpool L69 3GA

    EDITOR—In his clinical review on genetically modified foods Jones implies that Pusztai had tested only the effects of potato spiked with concanavalin A (a lectin) at the Rowett Institute.1 The initial dissemination of this incorrect information followed by the inappropriate suspension of Pusztai and the suspicion of fraud implied by instituting an audit according to Medical Research Council guidelines led some scientists, including me, to defend Pusztai, whom we know to be an honourable and careful scientist. The report of the audit conducted at the Rowett Institute (www.rri.sari.ac.uk/press) clearly shows that experiments on transgenic potatoes containing the gene for the snowdrop lectin (GNA) had already been performed when Pusztai was interviewed for World in Action in August 1998. If the Rowett Institute had released a statement that the work was preliminary and allowed the work to continue such a potentially damaging media storm would probably not have happened.

    Not all lectins are toxic. They are ubiquitous carbohydrate binding proteins. All mammalian cells and blood and all plant nuts, seeds, and bulbs, including many non-toxic food components, contain lectins.2 Some of these, in red kidney beans for example, are toxic and need to be destroyed by heat before consumption,3 but others such as tomato lectin are apparently harmless when eaten raw. Many plant lectins have an insecticidal or antifungal role in the plant. Some of these food lectins have interesting biological effects. We have recently shown that the common edible mushroom lectin that is often eaten raw selectively inhibits nuclear protein import.4 The snowdrop lectin (GNA) binds to mannose, which is minimally expressed in mammalian intestine but extensively expressed in the intestine of sap sucking insects. Thus expression of this lectin in food plants might render them unattractive to insects but safe for human consumption, particularly if the food (potato) is always cooked before ingestion.

    Pusztai's experiments, whatever their results, would not show that all genetically modified foods were unsafe. Pusztai's message was simply that such foods require careful testing. As with the testing of new pharmaceutical agents, some transgenic foods will prove toxic or otherwise unsatisfactory and be discarded at an early stage of development.

    The fact that Pusztai has been barred from continuing his experiments since the time of his initial suspension has meant that his data remain preliminary, and further experimentation will probably be needed before any final conclusions can be drawn about the effects of the transgenic GNA potato or its promoter.

    There has been little clarity surrounding this debate, and one lesson that needs to be learnt is that all scientists need to be careful to ensure that their comments inform rather than confuse when handling issues that are of such extreme public interest.


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