1.16—Rats fed Roundup Ready Canola have healthy livers

Feeding Roundup Ready canola to rats had no effect on the weights of their livers

See Genetic Roulette’s False Claims at Bottom of Page

Analysis of Peer-Reviewed Research:

First, it should be said that the feeding tests mentioned in Genetic Roulette were carried out on canola meal, which is not used in food. Edible canola oil is separated from the meal during processing, and the meal is unsuitable as a food.

The slight increase in weight of the rat livers observed in this study can be attributed to glucosinolate content, which is a known toxic component of the meal that causes enlargement of liver and other organs.  Smith does not tell the reader that this relationship is well described in the scientific literature, and appears in standard textbooks (Hayes 1989).  Also not revealed by Smith is a third comprehensive rat-feeding study on this variety of  GM canola (FSANZ 2004) in which no difference from non-GM canola meal in effect on liver size or any other relevant health parameter was found.  His claim “that researchers did not undertake additional studies” is thus wrong.  The GM canola in question has been approved by regulatory authorities in a number of countries.  Once again Smith asks us to believe that regulators approve crops in spite of dangerous toxic effects.

1.  Other studies show no effect of RR-canola on liver weight. Smith neglects to tell the reader that 3 careful studies have been performed with Roundup Ready Canola.  In the first and very thorough third study, no differences in liver weights were observed. The Australian food regulator FSANZ describes this third study as follows:

“The third study was an assessment of the GM (GT73) canola meal, non-GM control lines from around the world, and rat chow as a negative control. On this occasion, all seed samples from the GM and non-GM lines were processed at the same time, and to the same extent. There were no significant differences in body weight, cumulative weight gain, terminal body weights or food consumption for animals fed GM canola meal compared to the non-GM control canola meal. Most importantly, there were also no significant differences in absolute or relative liver or kidney weights between animals fed the GM canola meal compared to the non-GM canola meal, or the population of canola varieties.” (FSANZ 2004). Smith quotes extensive correspondence with FSANZ but avoids mentioning widely publicized responses from them that refute his claims.

2.  It is known that a toxic compound, glucosinolate, can increase liver weight. The literature shows that rat liver weight varies directly with the glucosinolate content of the canola when rats are fed canola—this is called a dose-response relationship.  The literature also shows that different batches of all varieties of canola, including both conventional and GM canola, have variable amounts of glucosinolate.

3.  The simplest best explanation, glucosinolate, was ignored. The only reasonable explanation for the results observed in the second experiment is that the GM canola used in the experiment had higher levels of glucosinolate.  (Occams razor—the simplest and most obvious explanation should be preferred).

4.  Glucosinolate content varies by batch to batch in all kinds of canola. The GM nature of the canola has no effect on glucosinolate.  Smith obscures from the reader the most likely explanation for the observation in his zeal to cast doubt on GM crops.  Regulatory authorities in Canada, Australia, USA, Japan and several others have a reviewed the safety data and approved Roundup Ready canola.

5. The newly introduced proteins and other components in GM-canola have been thoroughly evaluated for toxicity (ANZFA 2000, FSANZ 2004, Harrison and others 1996).

References

ANZFA (2000) Final risk analysis report application A363. Food produced from glyphosate-tolerant canola line GT73.16 October 2000 www.foodstandards.gov.au/_srcfiles/A363%20draft%20IR.pdf accessed Mar 14 2010 (ANZFA is now FSANZ).

FSANZ (2004). GM Canola safety assessments, 28 June 2004. www.foodstandards.gov.au/newsroom/factsheets/factsheets2004/gmcanolasafetyassess2498.cfm accessed Mar 14 2010.

Harrison LA, Bailey MR, Naylor MW, Ream JE, Hammond BG, Nida DL, Burnette BL, Nickson TE, Mitsky TA, Taylor ML, Fuchs RL, Padgette SR (1996). The expressed protein in glyphosate-tolerant soybean, 5-enolpyruvylshikimate-3-phosphate synthase from Agrobacterium sp. strain CP4, is rapidly digested in vitro and is not toxic to acutely gavaged mice.J Nutr. 126(3):728-40.Hayes AH, (1989) Foodborne toxicants, (p69 on glucosinolates) in Principles and Methods of Toxicology 2nd edition. Raven Press (and later editions). Effects of glucosinolates on rat liver enlargement are in standard textbooks.