GM issues | Is gm safe?|
Contents
Is GM food safe? (for animals or humans)
Briefing Paper prepared for presentation to the
National Farmers Union of Scotland Combinable Crops Committee
7th February, 2001
Introduction
1. Calgene's Flavrsavr tomatoes, 1993
2. Glyphosatelherbicidel-tolerant soybeans, 1996
3. Pest resistant potatoes Bacillus thuringiensis, transformed with the Cryl gene of 1998
4. GNA Lectin-producing, nematode-resistant potatoes, 1999
5. Glufosinatetweedkillerl-tolerant Maize T25, 1999
INTRODUCTION
The danger to livestock from eating GM food may be considerably greater than the danger to humans. This is because farm animals eat a fairly restricted diet, so that a high proportion of their feed is likely to be derived from GM plants. However, humans face possible adverse consequences from eating GM plants and from eating animal products affected by GM feed. Also, because of our varied diet, we have the added danger of synergistic ill effects from the consumption of multiple GM foods.
Feeding studies are extremely difficult to perform. Their scope is severely limited by the natural diet of the test animals and extrapolation between species is always uncertain. Healthy, adult animals will be least likely to demonstrate adverse effects, while stressed or developing animals will be most susceptible. Short-term experiments are only likely to reveal acute problems.
An overview of GM feeding studies
1. Calgene's Flavrsavr tomatoes, 1993
An unpublished zs-day feeding study on rats was found in the US Federal Register. The experiment was so flawed that no conclusions could be drawn, and the attempt to prove safety by such means seems to have been abandoned.
Reference: www.biointegrity.org
2. Glyphosatelherbicidel-tolerant soybeans, 1996
A published study commissioned by Monsanto examined the feeding of GM soya to dairy cows, chickens, rats and catfish. Measured parameters mainly concentrated on feed conversion and chosen organ weights. Histological (tissue) studies were not included.
Differences were noted in the fat content of the cows' milk. A ''significant'' but ''not meaningful'' reduction in the growth of male rats fed processed GM soya was seen. A thirteen per cent increase in kidney weight occurred in two groups of rats fed unprocessed GM soya (unprocessed soybean meal has been found to stress the pancreas). Studies of the gastro-intestinal tract were not carried out.
Reference: Hammond B.G et at. The feeding value of soybeans fed to rats, chickens, catfish and dairy cattle is not altered by genetic incorporation of glyphosate tolerance. .3. Nutr 1 26 717-27 ( 1996 )
3. Pest resistant potatoes Bacillus thuringiensis, transformed with the Cryl gene of 1998
Using light and electron microscopy, mild changes were found in the structural configuration of the ileum (small intestine) of mice fed transgenic potatoes.
Reference: Fares N.H. and El-sayed A.K. Fine structural changes in the ileum of mice fed on -Endotoxin-treated potatoes and transgenic potatoes.
Natural Toxins # 219-33 (1998)
4. GNA Lectin-producing, nematode-resistant potatoes, 1999
Arpad Pusztai was forced to prematurely halt his experimentation and publish incomplete data when he found histologlcal changes in the gastro-intestinal tract of rats fed on GM potatoes.
Reference: Ewen W.B. and Pusztai A. Effect of diets containing genetically modified potatoes expressing Galanthus finalis pectin on rat small intestine. The Lancet 354 1353-4 ( 1999)
5. Glufosinatetweedkillerl-tolerant Maize T25, 1999
An unpublished l4-day feeding trial carried out by AgrEvo reported that the weights of (apparently) well-fed, adult animals was unaffected. No histologists studies seem to have been made.
Reference: Howard C.V., toxico-pathologist. Expert evidence given at the trial of 28 Greenpeace activists and AgrEvo. ''GM on trial'' (Greenpeace, 2000)
Substantial equivalence (or, how long is a piece of string?)
Substantial equivalence means 'about the same as'. Food safety studies are based on the concept of substantial equivalence. Compositional analyses of GM material and that of an undefined equivalent are carried out. If they are about the same as each other, the food is safe.
Known anti-nutrients are also tested to ensure that GM foods do not contain enhanced levels. This can be challenging because in most cases, the scientific literature does not provide clear consensus as to which compounds contribute to anti-nutritive properties. Unknown toxins, of course, remain unknown.
Reference: Padgette S.R. et at. The composition of glyphosate-tolerant soybean seeds is equivalent to that of conventional soybeans. J. Nutr. 126 702-16 (1996 )
This briefing paper was produced by Genetic Engineering Network Scotland using as much scientific literature as could be accessed and read. It is not exhaustive, and will be subject to on-going amendments. The text was prepared with the non-scientific of our community in mind, and, to that purpose, our comments are intended to clarify the implications of the scientific observations described; scientists should be able to read the literature for themselves.
We welcome comments.