Intended for healthcare professionals


The paradoxes of genetically modified foods

BMJ 1999; 318 doi: (Published 27 February 1999) Cite this as: BMJ 1999;318:547

A climate of mistrust is obscuring the many different facets of genetic modification

  1. Bernard Dixon, Science writer.
  1. 130 Cornwall Road, Ruislip Manor, Middlesex HA4 6AW

    Clinical Review p 581 Reviews p 611

    Celebrity chefs, Friends of the Earth, Greenpeace, and the Prince of Wales are among the voices that have raised the temperature of public debate in the United Kingdom over what newspapers call “Frankenstein foods.” Their expressions of concern, and in some cases calls for moratoriums, contrast with the verdict of a House of Lords committee that the potential benefits of genetically manipulated foods far outweigh any risks that may be involved.1 The furore seems inexplicable to observers in those parts of the world, including the United States, where genetical1y modified crops are being grown on a large scale and have been widely accepted.

    At the heart of the British debate is a gulf between plant breeders, seed companies, and agrochemical companies —who want to use recombinant DNA technology to facilitate the production of, for example, crops that are resistant to insects, viruses, and drought and improve food quality and nutritional value (p 581)2 —and campaigners who argue that any gene, newly introduced into one plant, may have hazardous consequences if transferred and expressed elsewhere in space and time. Scientists want to exploit the technology —which they also claim to be necessary to help feed the world's burgeoning population.3 Opponents, mistrustful of existing regulatory mechanisms, believe that transgenic techniques are unacceptable because they can ferry genes across “natural” boundaries.

    The decision of Monsanto, which commands a large share of the agrochemical business, not to separate its geneticaly modified soya from the regular variety when preparing products such as soya flour for export has exacerbated the situation. It has angered consumer organisations, who quite reasonably ask for full labelling (now under consideration by the European Commission) and separation so that people who don't want to eat genetically modified food don't have to, and other companies, who resent Monsanto's unilateral action and its repercussions on public opinion.

    There is also widespread confusion about what “genetically modified” food actually means. Cheese made using recombinant chymosin, soya flour containing denatured DNA, and vegetables actually carrying transgenes (though not yet on the market) are three very different products resulting from genetic manipulation. Although increasingly lumped together in public and media discussion, there is no objective reason why they should be either condemned or accepted as a single category.

    The debate is also replete with paradoxes. Firstly, alarming headlines contrast with the fact that genetic engineering is regulated more keenly and transparently than any other technology in the past. Secondly, activists are destroying field trials specifically established to help in assessing the environmental impact of transgenic plants. Thirdly, critics talk of the imprecision of the new plant breeding methods. Yet these involve the transfer of one or at most a few genes—not entire chunks of genomes, as in traditional plant breeding—and contrast starkly with the randomness of nature itself.2 Fourthly, the engineering of disease resistant plants, though opposed by some environmentalists today is an example of the very approach that the pioneer environmentalist Rachael Carson advocated as preferable to the use of chemicals.4

    Then there is the oft quoted danger that transgenic plants may prove to be allergenic. In reality, the new technology offers a promising route through which this undesirable trait can be “bred out” of plants which produce allergens naturally. Moreover, bodies such as the United Kingdom's Advisory Committee on Releases to the Environment specifically address the question of inadvertent allergenicity.

    Finally, campaigners increasingly cite bovine spongiform encephalopathy as the basis for rejecting genetically modified foods, though bovine spongiform encephalopathy has nothing to do with genetic manipulation. The only concrete link between the two is that the bovine spongiform encephalopathy epidemic may well have been avoided altogether if animal feedstuffs had been subjected to controls as stringent as those applied to transgenic plants.

    For the medical profession the row over genetically modified foods also contrasts oddly with the widespread acceptance and use of many recombinant products in health care. These include human insulin and growth hormone, erythropoietin, hepatitis B vaccine, tissue plasminogen activator, several interferons, factor VIII, and antihaemophilic factor. As pointed out by Bauer et al on the basis of focus group research in the United Kingdom, many people welcome medical applications of gene technology as “good genetics” but see genetically modified foods as “bad genetics.”5

    The constellation of paradoxes surrounding genetically modified foods should not, of course, blind us to the fact that potential hazards may accompany this technology, like any other. One obvious possibility is the transfer of genes from genetically modified crops to non-modified crops, where they may have unforeseen consequences. Yet, as observed in the Royal Society's recent report,6 well established practices already minimise such dangers in the case of conventional cultivars. For example, oilseed rape for human consumption contains low levels of erucic acid, which is toxic to humans, whereas industrial oilseed rape contains high levels. So the two varieties are grown sufficiently far apart to prevent cross pollination.

    Transfer of antibiotic resistance genes from genetically modified plants (where they are used as markers during the genetic manipulation process) to pathogenic bacteria is another theoretical danger.6 However, there is no evidence that this has happened. The risks are considered to be at most remote, especially in comparison to plasmid transfer from other bacteria. The Advisory Committee on Releases to the Environment has recommended that plants should not be produced with genes conferring resistance to antibiotics used in human and veterinary medicine. And drug resistance markers are now being supplanted by alternatives.

    One factor has heavily influenced the public debate on genetically modified foods in both the UK and continental Europe. This is the coincidence between their emergence and the outbreaks of bovine spongiform encephalopathy and Escherichia coli0157infection in the UK. Though apparently linked through their effects on public trust in the technology of food production, epidemics of food borne infection have no rational relation to the consideration of genetically modified plants.

    As announced at the European Biotechnology Forum, held in Brussels in December, the French seed supplier Groupe Limagrain will be segregating its genetically modified and non-modified plants by the middle of this year. Such a scheme will, however, be fully effective only if other companies along the food chain follow suit. The European Commission is now considering a threshold (possibly 3%) for the permissible level of genetically modified ingredients in foods from farm to plate.

    Prices will, of course, reflect the extra expense of segregation and the higher costs of growing conventional crops lacking the advantages (such as pest resistance) of genetically modified varieties. Some customers will be content to pay, as with organic produce today. Others will prefer the fruits of genetic manipulation, such as the tomato purée and cheese made with recombinant chymosin—which are already on sale. The fact that these explicitly labelled products have been selling well in the UK, where the debate is particularly robust, is the most remarkable paradox of all.


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