The Committee had not been asked to assess the safety of the particular lines of genetically modified (GM) potatoes tested in these studies as it was not intended that these GM potatoes would be released onto the market. However, given the fact that the results of the studies were widely publicised, and that they appeared to raise a number of generic questions about the safety assessment of GM foods, the Committee considered it essential that it should have an opportunity to review the studies. Unfortunately, despite frequent requests, the original study reports have not been made available to the Committee and it had to rely on a number of documents that were already in the public domain.
A series of studies had been carried out in rats using both raw and cooked GM and non-GM potatoes. In addition, raw and cooked potatoes spiked with either the snowdrop lectin or the jack bean lectin, concanavalin A (ConA) were also tested. The potatoes were included in the diet and were fed either for a period of 10 days or 110 days. Body weight gain was monitored throughout each study and at the end of each study, organ weight measurements were carried out. In one of the short term studies (10-day) tissue samples were taken from the gastrointestinal tract of rats fed either the GM potato (raw and cooked) or potato (raw and cooked) spiked with the snowdrop lectin, for histological examination. In addition, an assessment of immune function was performed in some of the studies using the lymphocyte proliferation assay.
It had been widely reported in the media that the GM potatoes tested in these studies produced an adverse effect on growth and immune function in rats. The histological findings were similarly publicised as indicating that the GM potatoes produced adverse effects in the gastrointestinal tract. Given the nature of these findings, the Committee asked that the available data be referred to the Committee on Toxicity (COT) for advice on the significance of these findings. The COT’s advice is detailed in the attached statement.
Having considered all the data made available, the ACNFP agreed with the COT that the studies were poorly designed and did not appear to be addressing any clear hypothesis. Some changes in body weight and organ weight were evident in some of the studies. However, although attempts had been made to ensure that the potato-supplemented diets were nutritionally adequate, there were serious doubts as to whether this had been achieved. The Committee noted that the nutritional adequacy and nutrient density of the diet could have an effect on body weight and organ weight. In addition, the effects of dietary restriction due to palatability problems did not appear to have been taken into consideration in the studies and this could also have been responsible for the weight changes observed, as well as the histological findings in the gut.
The Committee noted that the histopathological changes observed in the GI tract of animals fed the raw GM potatoes were also seen in rats fed raw potato spiked with the GNA lectin, although the changes observed in this group were quantitatively smaller than in rats fed the GM potatoes. The Committee also questioned the appropriateness of using raw potatoes in the studies, given that potatoes were not normally consumed in this way, and noted that feeding rats raw potato starch was well known to produce alterations of gut morphology. The Committee indicated that further work would be necessary in order to determine the nature of the changes observed in the GI tract.
The Committee noted that there was wide variation in the results of the lymphocyte proliferation assay that called into question the reliability of the assay in this instance. The Committee was of the view that it would be inappropriate to draw any conclusions on the effects of the GM potato on immune function based on the results of this assay alone.
The Committee also noted that the GM potatoes used in these studies were experimental lines that had not been subject to the further breeding steps necessary to produce a stable variety.
The Committee fully endorsed the views of the Committee on Toxicity and agreed that no meaningful conclusions could be drawn from the data made available on the effect of feeding rats GM potatoes expressing the snowdrop lectin. This was because of serious doubts about the design of the studies and the nutritional quality of the potato-supplemented diets that had been used. In addition some of the adverse effects seen occurred in rats fed potatoes spiked with the GNA lectin suggesting that these did not arise as a result of the genetic modification and could be explained by variability in lectin levels. Furthermore alterations in gut morphology similar to those seen in these studies are known to occur in animals fed raw starch from conventional potatoes and it was not clear from the information provided that the potatoes used in each of the studies were identical in all respects except for the parameters being assessed.
Some plant lectins are known to be toxic to animals and the Committee stressed the need to carefully assess any GM foods modified to express lectins. If any toxicology studies were conducted as part of the safety assessment they would need to be carefully designed and controlled.
1. Bourne FJ, Chesson A, Davies H and Flint H (1998). SOAEFD flexible fund project RO 818: Audit of data produced at the Rowett Research Institute (Date of audit: 21 August 1998.
2. Bourne FJ, Chesson A, Davies H and Flint H (1999). The Audit Committee’s Response to Dr Arpad Pusztai’s Alternative Report of 22 October 1998. 16 February 1999.
3. Ewen SWB and Pusztai A (1999). Diets containing genetically modified (GM) potatoes expressing Galanthus nivalis (GNA) lectin are associated with proliferation of the mucosal cells of the rat gut, unpublished manuscript.
4. Horgan GW and Glasbey CA (1999). Statistical analysis of experiments on genetically modified potatoes conducted at the Rowett Research Institute. Preliminary Report. 1 March 1999. Biomathematics and Statistics Scotland.
5. Pusztai A (1998). SOAEFD Flexible Fund Project RO 818: Report of Project Coordinator on data produced at the Rowett Research Institute (RRI). [22 October 1998].