London (12.11.08) – Experience has proven that legitimate scientific findings are disclosed through professional peer review processes, not through the media or NGO press releases.

Nevertheless, three years ago reports came from Moscow of experiments which purported to show that rats fed GM soya resulted in a 6-fold increase in the number of deaths and the surviving progeny were significantly smaller ( There were other problems as well.

The information was first revealed at a conference and later appeared in review on an anti-GM activist website (1). A fully referenced version was offered to members of that organisation; scientific transparency par excellence.

Many people expressed doubt at the time, scepticism well placed as the work has never been published in the scientific literature. Nevertheless, from such material as was available in the public domain, it was clear that the study had little or no value as a piece of scientific research; an interview with the original author together with the scientific criticisms subsequently appeared in a legitimate scientific journal which well illustrated the poor quality both of the study and how unjustified were the claims made (2). That brought forth a rebuttal from the original author (3) and screams of indignation from the activist camp (4), encouraging the journal’s editor to write: “I am also struck that none of the correspondence elicited by the article has taken issue with the validity of the scientific criticisms made, only the identity of the authors who made them” (5). Once more the data was revealed as wholly inadequate (6).

Are we about to see a repeat performance, this time from Vienna? In a study published by the Austrian Federal Ministry for Health, Family and Youth (7) and rapidly reproduced on an activist website (8, 9), we read about new claims: “Austrian scientists performed several long-term feeding trials with laboratory mice over a course of 20 weeks. One test - the so-called "reproductive assessment by continuous breeding" showed that mouse parents fed on a diet containing 33 percent of a Monsanto owned GE maize variety (NK 603 x MON 810) experienced a decrease in litter size and weight by the time they gave birth to their third and fourth litters. Mice fed on a closely-related non-GE maize had normal reproduction cycles”. Summarising his findings, Prof. Dr. Jürgen Zentek, Professor of Veterinary Medicine at the University of Vienna - the lead author of the study - said the differences between the mice was statistically significant, and that this effect could be attributed to the differences in food sources (9).

What is missing is peer review. No conclusions can justifiably be drawn from these findings until they are examined and compared with previously published and peer-reviewed studies by people with experience and understanding of the field. The report already published is more than 100 pages long and apparently packed with experimental data; we await with interest a review by experts.

Nevertheless, even at this stage, a number of points come to mind:

(a) Conducting a study using reproductive assessment by continuous breeding (RACB) involves a set of fecund mice producing successive litters. Each successive litter is therefore born to increasingly aged parents. As a result, a decline in the number of offspring in each litter is an expected outcome in a mouse breeding program. Furthermore, certain strains of mice have distinct reproductive traits/deficits, some of them severe. Not knowing the strain(s) of mice involved makes interpretation at this remove utterly impossible. It had, moreover, been noted that the number of pups per litter and the number of pairs delivering a litter both tended to decline with time, so that fewer pairs produced slightly smaller litters for litters four and five (10).

(b) From the Guidelines for Reproductive Toxicity Risk Assessment: "Because the parental and subsequent filial generations have different exposure histories, reproductive effects seen in any particular generation are not necessarily comparable with those of another generation. Also, successive litters from the same parents cannot be considered as replicates because of factors such as continuing exposure of the parents, increased parental age, sexual experience, and parity of the females" (11).

(c) "In general, the first few litters born to most female lab animals are smaller in number than later litters. There is also a tendency for females to offer poorer maternal care to earlier litters. This may result in a higher mortality rate among early litters than among later ones. As these animals approach the end of their reproductive lives, litter size again tends to be smaller….Breeders usually remove females and/or their mates from the breeding program as soon as litter size begins to decline. Some do this at a specific age that is known to correspond with decreased fecundity" (12).

(d) This is not the first multi-generational animal study made with a GM-feed; many existing studies from different laboratories, including multi-generation animal feeding studies, have been conducted on biotech crops, studies which support their safety and showed no adverse affect on animal health. Those studies have been thoroughly reviewed by hundreds of independent scientists on behalf of regulatory authorities around the world and have completed regulatory review by a number of countries globally. The overwhelming opinion of expert authorities around the world is that MON 810 x NK603, the GM strains involved in the Austrian work, is safe to consume.

(e) Dr. Zentek has remarked that his team’s three studies show inconsistent results and should be considered preliminary.

The Austrian studies are important. Scientific inquiry does not stand still and is never completed. No matter how many studies have shown something to be safe, the possibility must always remain that further investigations will reveal dangers hitherto unsuspected. But always the critical factor is challenge and peer review so we await with interest the outcome of detailed scrutiny of the report already available by people with the experience and the ability to make an impartial assessment. Rushing to judgement either for or against the claims made in the report is campaigning, not science.


1. Mae-Wan Ho. GM soya fed rats: stunted, dead, or sterile. Institute of Science in Society Press Release (28.11.06) (

2. Andrew Marshall (Sep. 2007). GM soybeans and health safety – a controversy reexamined. Nature Biotechnology, 25(9), 981-987.

3. Irina V. Ermakova (Dec. 2007). GM soybeans—revisiting a controversial format - 1. Nature Biotechnology, 25(12), 1351-1354

4. Various authors (Dec. 2007). GM soybeans—revisiting a controversial format - 2-6. Nature Biotechnology, 25(12), 1354-1355, 1355, 1355, 1355-1356. 1356.

5. Andrew Marshall (Dec. 2007). GM soybeans—revisiting a controversial format - 8. Nature Biotechnology, 25(12), 1359-1360.

6. Bruce Chassy, Vivian Moses, Alan McHughen and Val Giddings (Dec. 2007). GM soybeans—revisiting a controversial format - 7. Nature Biotechnology, 25(12), 1356-1358.

7. A. Velimirov, C. Binter and J. Zentek (November 2008). Biological effects of transgenic maize NK603xMON810 fed in long term reproduction studies in mice. Austrian Federal Ministry for Health, Family and Youth Forschungsberichte der Sektion IV, Band 3/2008 (

8. Anon (11.11.08). Genetically-engineered food: potential threat to fertility. Greenpeace International (

9. Anon (11.11.08). Mice! Forget about birth control - try GE maize instead! Greenpeace International (

10. Robert E. Chapin and Richard A. Sloane(1997). Reproductive assessment by continuous breeding: evolving study design and summaries of ninety studies. Environmental Health Perspectives 105(Suppl 1), 199-395 (

11. U.S. Environmental Protection Agency (31.10.96). Guidelines for reproductive toxicity risk assessment. Federal Register, 61(212), 56274-56322 (

12. Anon (no date). Animal facilities and animal husbandry; mouse breeding advice. University of North Carolina, Division of Laboratory Animal Medicine (


  Here we go again? Or, this time, will it be different?