Science in Society Archive

GM food safe?

Recent incidents and scientific findings cast grave doubts over the safety of GM food and feed. We shall be circulating a selection of the following reports.

  1. Cows Ate GM Maize & Died
  2. Transgenic DNA and Bt Toxin Survive Digestion
  3. Bt Toxin Binds to Mouse Intestine
  4. Syngenta’s Spanish GM Trojan Horse
  5. Liver of Mice Fed GM Soya Works Overtime
  6. Animals Avoid GM, for Good Reasons

Bt Toxin Binds to Mouse Intestine

Years after Bt crops have been commercially released on millions of hectares worldwide, a Bt toxin is found to be highly immunogenic. Dr. Mae-Wan Ho reports.

Bt toxins are a large class of Cry proteins found in the soil bacterium Bacillus thuringiensis, which have been heavily exploited as ‘biopesticide’ in GM crops, on the fallacious, untested assumption that they are safe for species other than the target insect pests (see “Regulatory sham on Bt crops”, this issue).

These proteins have a high molecular weight, and are unusual for being resistant to enzymes that break down proteins and soluble at alkaline pH.

Researchers from the Center for Genetic Engineering and Biotechnology, Havana, Cuba, reported in 1999 that Cry1Ac is a powerful immunogen, and when fed to mice, induced antibody responses similar to those obtained with the cholera toxin.

In 2000, the Cuban researchers teamed up with scientists from the Autonomous University of Mexico (UNAM) in Cuautitla, Mexico and showed that Cry1Ac actively binds to the inner surface of the mouse small intestine, especially to the ‘brush border’ membranes on the side of the cells that line the small intestine.

Cry1Ac binding induced a transient hyperpolarization - increase in electrical potential in the cells - an effect that’s expected to have significant biological consequences.

The researchers identified 6 proteins in the brush border that bind specifically to Cry1Ac. They warned that, “it is necessary to perform toxicological tests to demonstrate the safety of CrylAc proteins for the mucosal tissue and for the immunological system of animals.”

Despite their warnings, no such toxicological tests have been performed.

Article first published 2004


  • Vázquez-Padrón RI, Gonzáles-Cabrera J, Garcia-Tovar C, Neri-Bazan L, Lopéz-Revilla R, Hernández M, Moreno-Fierro L and de la Riva GA. CrylAc protoxin from Bacillus thringiensis sp. kurstaki HD73 binds to surface proteins in the mouse small intestine. Biochem Biophys Res Commun 2000, 271, 54-8.

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