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For each rat at 33% GM maize feed level (a) and controls (b) the lines represent the variations between week 5 and 14 for this parameter (ml/min/100 g body weight). The dotted thick line represents the means variation.

Fig 4 

Kinetic plot for female rat triglyceride levels in the MON 863 feeding trial.

For each rat at 11% GM maize feed level (a) and controls (b) the lines represent the variations between week 5 and 14 for this parameter (mg/dL). The dotted thick line represents the mean variation.

Fig 5 

Kinetic plot for creatinine levels in female rats fed MON 863.

For each rat at 11% GM maize feeding level (a) and controls (b) the lines represent the variations between week 5 and 14 for this parameter (mg/dL). The dotted thick line represents the mean variation.

Fig 6 

Kinetic plot for urine chloride excretion in female rats fed MON 863.

For each rat at 33% GM feed level (a) and controls (b) the lines represent the variations between week 5 and 14 for this parameter (meq/time). The dotted thick line represents the mean variation.

Fig 7 

Kinetic plot for urine potassium in male rats fed MON 863.

For each rat at 11% GM maize level (a) and controls (b) the lines represent the variations between week 5 and 14 for this parameter (mmol/L). The dotted thick line represents the mean variation.

4. Discussion 

If a “sign of toxicity” may only provoke a reaction, pathology or a poisoning, a so-called “toxic effect” is without doubt deleterious on a short or a long term. Clearly, the statistically significant effects observed here for all three GM maize varieties investigated are signs of toxicity rather than proofs of toxicity, and this is essentially for three reasons. Firstly, the feeding trials in each case have been conducted only once, and with only one mammalian species. The experiments clearly need to be repeated preferably with more than one species of animal. Secondly, the length of feeding was at most only three months, and thus only relatively acute and medium-term effects can be observed if any similar to what can be derived in a process such as carcinogenesis [, ] or after endocrine disruption in adults []. Proof of toxicity is hard to decide on the basis of these conditions. Longer-term (up to 2 years) feeding experiments are clearly justified and indeed necessary. This requirement is supported by the fact that cancer, nervous and immune system diseases, and even reproductive disorders for examples can become apparent only after one or two years of a given intervention treatment under investigation, but they will not be evident in all cases after three months of administration when first signs of toxicity may be observed [, ]. In addition, large effects (e.g. 40% increase in triglycerides) in all likelihood will be missed with the protocol of the current studies, since they are limited by the number of animals used in each feeding group and by the nature of the parameters studied. Thirdly, the statistical power of the tests conducted is low (30%) because the experimental design of Monsanto (see Materials and Methods). However, it is important to note that these short-term (3-month) rat feeding trials are the only tests conducted on the basis of which regulators determine whether these GM crop/food varieties are as safe to eat as conventional types. Given that these GM crops are potentially eaten by billions of people and animals world-wide, it is important to discuss whether the experimental design, the statistical analyses and interpretations originally undertaken are appropriate and sufficient.

Any differences observed in comparison with the isogenic variety, has to be taken into account as a potential physiological disruption. This is particularly valid since any statistically differences that are observed are highly unlikely to be arising from population variation as in the case of humans due to the genetic homogeneity of the rat strain used in these studies. Moreover, the standardized conditions of rat maintenance employed, which are stated to be in accordance with OECD standards [, ], make the diet the only factor of variation in the protocol. Thus, the GM maize component of the test diet is the major factor of difference if one directly compares treated rats and controls. This is indicated by stars in the Tables expressing the total characteristics of GM-linked physio-pathological profiles. The other results that are encompassed by frames in the Tables highlight that effects from the GM maize are over and above those observed for any of the six different diets; for instance, over that observed with a diet richer in salt or sugar over the 3-month feeding period. These additional “control” diets could have been avoided with an experimental design that truly focused on the general question of GM toxicity.