Poisonous Potatoes

This weekend the Independent has run an article about an environmental pressure-group GM Watch publishing a report that claims that Genetically Modified (GM) potatoes are unsafe for human consumption. Upon further inspection this report was actually published by GM Free Cymru which I think puts it fairly in my patch. Why do I care about this?; I’m living in Wales and I used to be a molecular biologist.

The headline of the Independent article “Suppressed report shows cancer link to GM potatoes” would lead one to think that this report shows GM potatoes cause cancer in Rats: It doesn’t and they don’t.

So what does the report show? The first thing to mention is that this isn’t a full scientific paper. There is a great deal of detail missing from the description of the experiment but even without those details it is possible to draw some conclusions, although those conclusions differ markedly from those drawn by the Independent. To make us even more confident in the results the report leads off with

“The analysis of the relevant part of the Institute of Nutrition Report showed that the studies were not carried out according to the accepted protocols for the biomedical assessment of GM food and feed (1). Many of the conclusions drawn by the authors do not correspond to the obtained data and therefore they are incorrect.”

Three groups of 10 Wistar rats were fed on different diets for 6 months. These groups were:
Control – normal feed.
RB – normal feed plus boiled Russett Burbank potato.
RB-GM – normal feed plus boiled genetically modified Russett Burbank potato.

After six months the animals were killed so they could be autopsied. Both the RB group and the RB-GM group had lost weight relative to the Control with the RB-GM group having lost the most weight. Both the RB group and the RB-GM group showed pathological changes in their livers. The RB-GM group is described as having the worst changes but it is not described how that determination was made.

Taking this at face value it clearly shows that Russet Burbank potatoes and genetically modified Russet Burbank potatoes are poisonous to Rats (and by extension to humans). There is one small problem with this: the Russett Burbank has been in commercial cultivation since 1871 and is one of the most widely grown varieties of potato on the planet. If it’s as poisonous as the report makes out then people should be dropping dead of potato poisoning left,right and centre.
So why are these rats showing pathology? My suspicion (there aren’t enough details given of the protocol to know for sure) is that the various diets were either not calorie controlled (i.e normal diet plus loads of potato) or they were calorie conrolled without compensating for nutrient changed in the diet (i.e reduce the amount of cereal/grain to keep the calories constant but now the rats are missing out on lots of vital vitamins and minerals which are not present in the potato).

Which brings us on to the bit about cancer. Nowhere in the report is cancer mentioned. It doesn’t even mention the word tumor. So I can only conclude that the Independent made that bit up out of whole-cloth.

In short, both the Independent article and the report it cites are trash from start to finish.

For a more reasonable take on these particular GM potatoes one can read the report from the Canadian Food Inspection Agency which licensed these genetically modified potatoes for sale in 1996. You’ll note that this report mentions toxicology studies in mice which showed no adverse effects. I’ve emailed the agency to see if it’s possible to get the details of these experiments.