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 (http://www.cropgen.org/article_45.html).
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.
Sources:
1. Mae-Wan Ho. GM soya fed rats: stunted, dead, or sterile. Institute
of Science in Society Press Release (28.11.06) (http://www.i-sis.org.uk/GM_Soya_Fed_Rats.php)
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 (http://www.bmgfj.gv.at/cms/site/attachments/3/2/9/CH0810/CMS1226492832306/forschungsbericht_3-2008.pdf)
8. Anon (11.11.08). Genetically-engineered food: potential threat to fertility.
Greenpeace International (http://www.greenpeace.org/international/press/releases/ge-threat-to-fertility-11112008)
9. Anon (11.11.08). Mice! Forget about birth control - try GE maize instead!
Greenpeace International (http://www.greenpeace.org/international/news/of-mice-and-ge-maize-11112008)
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 (http://www.ehponline.org/members/1997/Suppl-1/chapin-full.html)
11. U.S. Environmental Protection Agency (31.10.96). Guidelines for reproductive
toxicity risk assessment. Federal Register, 61(212), 56274-56322 (http://www.epa.gov/ncea/raf/pdfs/repro51.pdf)
12. Anon (no date).
Animal facilities and animal husbandry; mouse breeding advice. University
of North Carolina, Division of Laboratory Animal Medicine (http://research.unc.edu/dlam/mousebreeding.htm)
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