1.2—GM Tomatoes Proven Safe

GM tomatoes don’t kill rats.

See Genetic Roulette’s False Claims at Bottom of Page

Analysis of Peer-Reviewed Research: The claim that GM tomatoes killed rats illustrates one of the common problems of Genetic Roulette—telling the story inaccurately.  FDA records clearly show that experts stated that the process of introducing stomach tubes can damage the rats’ stomachs and/or end up placing test material in the lungs.  Smith states that a number of rat deaths were observed but the regulatory discussion is about gastric erosions—not deaths.  The reader is not told that the study was repeated and no gastric erosions occurred.   The reader is not told that regulators approved the tomato because their concerns had been fully satisfied that the GM tomato was not toxic.  Smith is actually asking the reader to believe that the FDA would approve a lethal product.

1. No real differences were seen between groups of animals in the study. Contrary to Smith’s claims, expert pathologists stated that mild gastric erosions were seen at similar levels in both GM and non-GM fed rats (European Commission 2000, FDA 1994).

2. There is no evidence of  animal deaths. The numbers and details given by Smith about rats fatalities appear to be factually incorrect,  Smith may have confused the words necrosis and dead cells with animal deaths.  Careful reading reveals that the regulatory record does not mention any animal deaths which surely would have been of concern had they occurred.*

3. Pathologists say injuries could have occurred during the insertion of gastric tubes. Genetic Roulette fails to disclose the pathologists’ conclusions — that rats might have been injured during laboratory experiments by accidental administration of test material into the lung instead of the stomach (FDA 1994). More importantly, Genetic Roulette neglects to mention that experts concluded that the animals didn’t suffer lesions because of GM tomatoes; gastric lesions can be caused by  of acidosis brought on by fasting (FDA 1993).

4. Interestingly, eating too many tomatoes can kill rats. This study shows how difficult whole food feeding studies are to do.  The amount of tomatoes rats were fed was equivalent to a human eating 10-20 large tomatoes a day.  Other studies have concluded that 13 tomatoes/day are sufficient to kill about half of the rats because tomatoes contain a lot of potassium and too much  potassium can be lethal (Chassy and others  2004, MacKenzie 1999).

5. Claims about animal studies should be viewed with great caution. It is very difficult to do animal feeding studies with whole foods correctly. Great care must be taken in the design, execution and analysis of such studies.   Investigators must be very careful to reproduce and test their results since false positives are common (Parrott and Chassy 2009).  To date not a single rigorous study of GM foods in animals has revealed any adverse effect (EFSA 2008).  This should not come as a surprise since these products are assessed carefully for safety before they are marketed, and—more importantly—there is no scientific reason to believe they pose and new or different risks.

* The first mention we could find in the literature that rats died after eating Calgene’s tomatoes was in an article published in 2003 (Pusztai and others 2003) in which the authors claimed writing of these same studies: “This is the more serious because seven out of 40 rats eating GM tomatoes died within 2 weeks. The nature of these deaths was not specified and the evidence that they were not related to the ingestion of transgenic tomatoes was inconclusive (Bold emphasis added).  This claim (in Pusztai and others 2003) appears to be blatantly untrue, based on a reading of the regulatory discussion, and while not cited by Smith in Genetic Roulette may be the source of an urban legend that GM tomatoes killed rats.


Chassy BM and others. ILSI International Food Biotechnology Committee (2004) Nutritional and safety assessments of foods and feeds nutritionally improved through biotechnology. Comprehensive Reviews in Food Science and Food Safety. 3: 38-104.(pages 67-69).

EFSA (2008). Safety and nutritional assessment of GM plants and derived foodand feed: The role of animal feeding trials.

Food and Chemical Toxicology 46 : S2–S70 European Commission (2000) CS/NF/TOM/8 ADD 1 REV 3 Final. Opinion of the Scientific Committe on Food on the evaluatio of toxicological related to the safety assessment of genetically modified tomatoes. Adopted on 7 September 2000. ec.europa.eu/food/fs/sc/scf/out69_en.pdf available at Agbios GM database.

CGN-89564-2 (FLAVR SAVR). www.agbios.com/dbase.php?action=Submit&evidx=69 accessed Mar 14 2010 FDA (1993). Series of documents cited by Jeffrey Smith at www.biointegrity.org

FDA (1994). Summary of consultation with Calgene, Inc concerning FLAVT SAVR TM tomatoes, available at Agbios GM database. CGN-89564-2 (FLAVR SAVR). www.agbios.com/dbase.php?action=Submit&evidx=69 accessed Mar 14 2010

IFT Expert Report on Biotechnology and Foods. (2000). 56 pages. 27 authors. (see pages 20-21) MacKenzie, D. (1999). Unpalatable truths. New Scientist, April 17, pp. 18-19.

Parrot W and Chassy BM (2009), Is this study believable? Examples from animal studies with GM foods. www.agribiotech.info/details/Is%20This%20Study%20Believable%20V6%20final%2002%20print.pdf

Pusztai A, BardoczS, Ewen SWB (2003). Genetically modified foods: Potential Human Health Effects. In: D’Mello, J.P.F. (Ed.), Food Safety: Contaminants and Toxins. CABI Publishing, Wallingford, Oxon, pp. 347–372.

Redenbaugh K. and others (1992). Safety Assessment of Genetically Engineered Fruits and Vegetables: A Case Study of the FlavrSavrTM Tomato. CRC Press, Boca Raton, Florida.

Genetic Roulette Falsely Claims: Rats fed GM tomatoes got bleeding stomachs, several died

  1. Rats were fed genetically modified FlavrSavr tomato for 28 days.
  2. Of the 20 rats, seven developed bleeding stomachs, and another seven of 40 died within two weeks.

Genetic Roulette claims that in 1993 rats died after being fed GM FlavrSavrTM tomatoes but the FDA approved them anyway.