1.4—These aren’t even GM Potatoes!

Mouse feeding tests show GM technology is a safer way of delivering protection of crops from insects with the Bt-protein insect than is the traditional delivery method.

See Genetic Roulette’s False Claims at Bottom of Page

Analysis of Peer-Reviewed Research: In this study, a preparation of Bt protein isolated from bacteria apparently caused minor changes to mouse intestines.  Experts have attributed these kinds of changes to impurities in the bacterial preparation—it is important to recognize that some bacteria that produce Bt make several toxic proteins.  The GM potatoes themselves caused no such effects. The authors of the paper on which the claim is based conclude only that a proper safety assessment should be done on GM crops in order to avoid any adverse effects.  GM crops are of course subjected to years of very careful safety studies before they are approved by regulatory agencies. If anything, the investigation demonstrates that GM technology is safer than the traditional method for delivering crop protect against insect attach via the Bt protein.

  1. The researchers Smith refers to, Fares and El-Sayed, did not study GM potatoes! Jeffrey Smith wrongly attributes results to genetically modified potatoes that were obtained only with potatoes supplemented with Bt toxin made in non-GM bacteria. His speculation about possible health effects is irrelevant to the issue of plant genetic modification.  Bt proteins have a long history of safe use, including prolonged use by organic growers, and there is an extensive literature on their safety.
  2. The effects reported are most likely due to toxic contaminants. Fares and El-Sayed used an uncharacterized bacterial strain as a source of Bt protein.  They refer to the strain as a serovar Bt kurastski named HD14, however, the strain carrying that name is a Bt thuringiensis (Seigel, 2001).   A major problem with isolating Bt from bacteria is that it is often contaminated with potent toxins that are unrelated to Bt (Seigel, 2001).  One would not expect a non-expert like Smith to be aware of that unrelated cytotoxins are often present in crude Bt preparations.
  3. The authors do not make any negative conclusions about GM technology. Smith says “The study does, however, indicate that damage to intestinal cells was due to Bt toxin.”  Note that Smith is not talking about transgenic potatoes, he is talking about the effects of an impure non-GM Bt preparation isolated from an uncharacterized bacterial strain.
  4. There are serious methodological deficiencies in the Fares and El-Sayed study. The authors did not determine the purity of their Bt preparation (critical because of the toxin problem mentioned in #2 above).  They also did not measure the amount of Bt or spores that were administered to the animals and it is thus impossible for other scientists to attempt to replicate the work.  Like so many of the stories told in Genetic Roulette the report by Fares and El-Sayed is 10 years old and it has never been repeated or validated.   In the same timeframe many other studies that attest to the safety of Bt that Genetic Roulette doesn’t tell the reader about have been published.


Betz FS, Hammond BG, and Fuchs, RL. (2000). Safety and advantages of Bacillus thuringiensis-protected plants to control insect pests. Regulatory Toxicology and Pharmacology 32:156-177. A key review which summarizes the uses of Bt proteins to control insect pests in agriculture. Importantly provides key data substantiating the ~million-fold safety margins for Bt proteins

Fares NH, and El Sayed AK (1998). Fine structural changes in the ileum of mice fed on delta endotoxin-treated potatoes and transgenic potatoes.

Natural Toxins 6: 219–233. Siegel JP (2001). The mammalian safety of Bacillus thuringiensis– based insecticides. Journal of Invertebrate Pathology.  77:13-21

Genetic Roulette Falsely Claims: Mice fed GM Bt potatoes had intestinal damage

  1. Mice were fed with either GM potatoes engineered to produce Bt toxin or natural potatoes spiked with Bt toxin.
  2. Both diets created abnormal and excessive growth in the lower part of their small intestines
  3. Similar damage to the human small intestines might result in incontinence or flu-like symptoms, and may be precancerous.
  4. This study overturns the assumptions that Bt toxin is destroyed during digestion and is not biologically active in mammals.

Genetic Roulette claims that effects seen by Fares and El-Sayed in 1998 with a traditional non-GM bacterial Bt toxin were also obtained with potatoes genetically manipulated to make that toxin. It goes on to make a series of other claims about genetically engineered potatoes containing this Bt toxin.