Downloaded from bmj.com on 30 June 2009 Genetically modified foods and the Pusztai affair Jonathan M Rhodes BMJ 1999;318;1284 Updated information and services can be found at: http://bmj.com/cgi/content/full/318/7193/1284 These include: Rapid responses You can respond to this article at: http://bmj.com/cgi/eletter-submit/318/7193/1284 Email alerting Receive free email alerts when new articles cite this article - sign up in the box at service the top left of the article Topic collections Articles on similar topics can be found in the following collections Diet (2132 articles) Notes To Request Permissions go to: http://group.bmj.com/group/rights-licensing/permissions To order reprints go to: http://journals.bmj.com/cgi/reprintform To subscribe to BMJ go to: http://resources.bmj.com/bmj/subscribers Downloaded from bmj.com on 30 June 2009 Letters Website: www.bmj.com Email: [email protected] Genetically modified foods and the Pusztai affair Vitamin D deficiency Time for a tablet containing high doses of Editor—In his clinical review on geneti- non-toxic food components, contain vitamin D alone 2 cally modified foods Jones implies that lectins. Some of these, in red kidney beans Editor—I was heartened to read Comp- Pusztai had tested only the effects of potato for example, are toxic and need to be ston’s editorial calling for action on vitamin 3 spiked with concanavalin A (a lectin) at the destroyed by heat before consumption, but D deficiency.1 Another point should be 1 Rowett Institute. The initial dissemination others such as tomato lectin are apparently made to encourage a more active role by the of this incorrect information followed by harmless when eaten raw. Many plant health service. the inappropriate suspension of Pusztai and lectins have an insecticidal or antifungal The British National Formulary does not the suspicion of fraud implied by instituting role in the plant. Some of these food lectins include a tablet containing vitamin D alone an audit according to Medical Research have interesting biological effects. We have in reasonable dose. Prescribers can give a Council guidelines led some scientists, recently shown that the common edible calcium and vitamin D mixture, which may including me, to defend Pusztai, whom we mushroom lectin that is often eaten raw be unpalatable and therefore impair compli- know to be an honourable and careful 4 selectively inhibits nuclear protein import. ance. Alternatively, a vitamin capsule can be scientist. The report of the audit conducted The snowdrop lectin (GNA) binds to prescribed containing many other vitamins. at the Rowett Institute (www.rri.sari.ac.uk/ mannose, which is minimally expressed in If a dose greater than minimal daily require- press) clearly shows that experiments on ments is needed higher doses of unneces- transgenic potatoes containing the gene for mammalian intestine but extensively expressed in the intestine of sap sucking sary vitamins must also be given. Surely it the snowdrop lectin (GNA) had already should be easy to prescribe 500-1000 units insects. Thus expression of this lectin in been performed when Pusztai was inter- of vitamin D daily without any other food plants might render them unattractive viewed for World in Action in August 1998. addition? If the Rowett Institute had released a to insects but safe for human consumption, particularly if the food (potato) is always C H Cheetham Consultant paediatrician statement that the work was preliminary Wycombe General Hospital, High Wycombe, and allowed the work to continue such a cooked before ingestion. Buckinghamshire HP11 2TT potentially damaging media storm would Pusztai’s experiments, whatever their [email protected] probably not have happened. results, would not show that all genetically Not all lectins are toxic. They are modified foods were unsafe. Pusztai’s mes- 1 Compston JE. Vitamin D deficiency: time for action. BMJ 1998;317:1466-7. (28 November.) ubiquitous carbohydrate binding proteins. sage was simply that such foods require All mammalian cells and blood and all careful testing. As with the testing of new plant nuts, seeds, and bulbs, including many pharmaceutical agents, some transgenic Groups at risk need supplementation, and milk could be fortified foods will prove toxic or otherwise unsatis- factory and be discarded at an early stage of Editor—We agree with Compston that the time has come for reappraisal of measures Advice to authors development. aimed at preventing vitamin D deficiency We prefer to receive all responses electronically, The fact that Pusztai has been barred from continuing his experiments since the with consequent bone loss predisposing to sent either directly to our website or to the osteoporotic fracture.1 The high prevalence time of his initial suspension has meant that editorial office as email or on a disk. Processing of vitamin D deficiency and secondary his data remain preliminary, and further your letter will be delayed unless it arrives in an hyperparathyroidism with high bone turn- experimentation will probably be needed electronic form. over emphasises this urgent need. before any final conclusions can be drawn We are now posting all direct submissions to The adequacy of current vitamin D about the effects of the transgenic GNA our website within 72 hours of receipt and our intake recommendations is being ques- intention is to post all other electronic potato or its promoter. tioned. The most sensitive yardstick for submissions there as well. All responses will be There has been little clarity surrounding ascertaining the degree of hypovitaminosis eligible for publication in the paper journal. this debate, and one lesson that needs to be D that predisposes to bone disease is Responses should be under 400 words and learnt is that all scientists need to be careful secondary hyperparathyroidism. Vitamin D relate to articles published in the preceding to ensure that their comments inform rather deficiency is known to occur even at a < month. They should include 5 references, in the than confuse when handling issues that are serum 25-hydroxyvitamin D concentration Vancouver style, including one to the BMJ article of such extreme public interest. previously considered adequate—namely, to which they relate. We welcome illustrations. Professor of medicine 37.5 nmol/l. Over the past two years the Please supply each author’s current Jonathan M Rhodes University of Liverpool, Liverpool L69 3GA threshold has been found to exceed appointment and full address, and a phone or [email protected] 75 nmol/l in both middle aged2 and elderly3 fax number or email address for the people irrespective of calcium intake. corresponding author. We ask authors to declare Calcium intake can modulate parathyroid any competing interest. Please send a stamped 1 Jones L. Genetically modified foods. BMJ 1999;318:581-4. (27 February.) function and bone resorption even in addressed envelope if you would like to know 2 Rhodes JM. Beans means lectins. Gut 1999;44:593-4. subjects who are replete with vitamin D.3 3 Freed DW. Do dietary lectins cause disease? BMJ whether your letter has been accepted or rejected. While the outcome of studies comparing Letters will be edited and may be shortened. 1999;318:1023-4. (17 April.) 4 Yu L-G, Fernig DG, White MRH, Spiller DG, Appleton P, the effectiveness of supplementation with www.bmj.com Evans RC, et al. Edible mushroom (Agaricus bisporus) lec- low dose vitamin D with or without calcium tin, which reversibly inhibits epithelial cell proliferation, [email protected] blocks nuclear localization sequence-dependent nuclear in reducing the incidence of bone fracture is protein import. J Biol Chem 1999;274:4890-9. awaited, two courses of action are required. 1284 BMJ VOLUME 318 8 MAY 1999 www.bmj.com Letters Downloaded from bmj.com on 30 June 2009 The first is supplementing groups at risk taking antiepileptic drugs without supple- made for routine supplementation in such with vitamin D (400-800 IU/day) and mentation. Blanket prescribing of vitamin D subjects, with serum 25-hydroxyvitamin D calcium (500-1000 mg/day), which is safe has economic consequences. Supplementa- concentrations being measured to monitor and effective. The second is fortifying milk tion may unmask undiagnosed primary treatment. There is no reason why children as a public health measure to benefit both hyperparathyroidism. Furthermore, a dis- should not be supplemented with vitamin young4 and old5 people. tinction needs to be made between recom- D, although the dose may require adjust- Rosemarie Freaney Principal biochemist mendations on prophylaxis in patients ment. For other subjects at lower risk Malachi J McKenna Consultant endocrinologist starting treatment with antiepileptic drugs serum 25-hydroxyvitamin D concentrations Metabolism Laboratory, St Vincents Hospital, and the identification and treatment of should be determined to assess the need for Dublin 4, Republic of Ireland osteopenia and osteomalacia in patients supplementation; this should probably already receiving long term treatment, espe- include patients taking the newer anticon- 1 Compston JE. Vitamin D deficiency: time for action. BMJ 1998;317:1466-7. (28 November.) cially in the presence of other risk factors. vulsants since little is known about their 2 Chapuy MC, Preziosi P, Maamer M, Arnaud S, Galen P, Lina Nashef Consultant neurologist effects on vitamin D status. Even the higher Hercberg S, et al. Prevalence of vitamin D deficiency in an adult normal population. Osteoporos Int 1997;7:439-43. [email protected] doses of vitamin D required for patients 3 McKenna M, Freaney R. Secondary hyperparathyroidism Edmund Lamb Consultant clinical biochemist receiving anticonvulsant treatment are safe, in the elderly: means to defining hypovitaminosis D. Kent and Canterbury Hospital, Canterbury and the benefits of preventing hypovitami- Osteoporos Int 1997;8(suppl 2):S3-6. CT1 3NG 4 McKenna M, Freaney R, Byrne P, McBrinn Y, Murray B, nosis D are likely to far outweigh rare events Kelly M, et al.