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More on Pusztai Research from 'Pandora's Picnic Basket'

By Alan McHughen, University of California, Riverside, CA

The Royal Society report at the time on the Pusztai matter was clear that the central flaw was a lack of proper controls. Here is Pandora's Picnic Basket text (pp.141-143) on the matter:

No small potatoes: The importance of experimental controls

Dr Pusztai at the Rowett Institute provides another example of the trouble we can get into when trying to cut corners. Shortly after appearing on TV to tell the world of his findings, he was drawn and quartered by his employers. In an effort to defend himself, Dr Pusztai posted his version of the experiments and data on the web, appended as an 'alternate' report to the official Rowett Institute web page (http://www.rri.sari.ac.uk/press/).

Because of the public confusion and sometimes contradictory information emanating from Dr Pusztai and the Rowett Institute, The Royal Society conducted a thorough and comprehensive analysis of the incident, eventually publishing the report on their web site (http://www.royalsoc.ac.uk). The Royal Society sent a set of 'all available' data and documents to six impartial reviewers with combined expertise in statistical analysis, physiology, nutrition, genetics, immunology and clinical trials. The reviewers and the panel from the Royal Society concluded the research was faulty because:

* The experiments were poorly designed, the nutritional comparability of the GM and non-GM potatoes was uncertain, * Different diets were enriched without adequate controls, * Too few rats were tested and were given non-standard control diets, * Data analysis was improper and a failure to account for inconsistencies in results between experiments.

Overall, the Royal Society cautions the work is 'flawed in many aspects of design, execution and analysis and that no conclusions should be drawn from it.' They conclude 'We found no convincing evidence of adverse effects from GM potatoes'. In effect, they said Dr Pusztai's experiments lacked the appropriate controls and replications to draw any conclusions. The stated objective of Dr Pusztai's experiments was to determine the effect of feeding GM potatoes to rats, but the experimental design did not alloIw that objective to be addressed because there were no suitable controls.

For example, the GM potatoes and their respective non-GM parent potatoes were analyzed raw, boiled and baked. This is an important point, because potatoes are normally eaten after cooking. Cooking destroys many common food toxins, and the background data provided by Dr Pusztai shows this for the GM lectin. Raw GM potatoes have between 12 to 25 micro gram of lectin per gram of potato, boiled are less than 5 micro gram/g, and baked less than 0.1 micro gram/g. These values vary according to the specific line of potato and where they were grown.

Ordinary potatoes, of course, have no GNA lectins, but they do normally produce their own potato lectins and other antinutritional factors. Dr Pusztai also provides some of the data on other nutrient composition. Unfortunately, only some of the measurements were recorded. Dr Pusztai's team neglected to compile some of the compositional data, particularly on the baked, non-GM parent potatoes. No meaningful comparisons can be made without these baked non-GM controls measured in the same way as theI experimental group. By measuring only half of the sample, the results can only be described as, well, half-baked.

The experimental treatments included regular potatoes, regular potatoes spiked with additional lectin and lectin-producing GM potatoes. How hard would it have been to include a group of rats fed on a diet of potatoes genetically modified with non-functional DNA? Even with this additional treatment, though, the experiment would have to be repeated several times to generate meaningful valid data. Any indication that the problem was due to the GM would later have to be specifically challenged.

If only one benign GM potato line was used, we wouldn't know if the problem was due to the genetic modification process or, perhaps, the nature of that one GM line. Perhaps the introduced DNA had been inserted into the recipient potato DNA is such a way as to interfere with normal potato functions. Alternatively, perhaps that original potato line happened to be an off type, or a spontaneous mutant.

Another alternate explanation might be that the GM potato caused problems because of somaclonal variation occurring during the transformation process, as is known to occur irregularly. This possibility was raised by Dr Pusztai himself, but seemed to forget it when he drew his conclusions. In order to validly control for these factors, several different lines of GM potato would have to undergo feeding trials. But only if there was an indication the GM process itself was at fault. There wasn't. At best, his controls seemed more appropriate for assessing the effects of lectin on rats, but even that was questioned and rejected.


Prof. Alan McHughen is the author of "Pandora's Picnic Basket : The Potential and Hazards of Genetically Modified Foods"