Dangers of Genetically Engineered Foods
Are Genetically Engineered Foods Without DNA Safe???
Dr Michael Antoniou, Senior Lecturer in Molecular Pathology, London, UK.
Biotechnology adviser to the Society for the Promotion of Nutritional
The application last year for the growing within Europe of "Maximiser"
maize by Ciba-Geigy (now part of Novartis), caused a great deal of
controversy. Maximiser has been genetically engineered to produce it's own
pesticide. However, it also contains a gene which confers resistance to the
antibiotic ampicillin. This raised the problem that the ampicillin
resistance gene may be transferred to bacteria either in the soil (from
rotting vegetable matter) or in the gut of animals and humans who have
eaten products derived from Maximiser maize. As a result the
use of this important antibiotic in both clinical and veterinary medicine
could be compromised still further if the resistance gene is picked up by
harmful strains of bacteria. It was this concern that caused the UK's
Advisory Committee on Novel Foods and Processes (ACNFP) and the European
Parliament to quite rightly not approve the growth or use of unprocessed
products from Maximiser maize. Interestingly in the context of our present
discussion, the ACNFP and EU did nevertheless give the go-ahead for the
marketing of processed food products derived from this maize in which the
DNA is either destroyed (e.g. by cooking at high temperatures) or removed
as is the case in the extraction of corn oil.
Generally, regulatory authorities which assess the safety of genetically
engineered (GE) foods, take the position that a processed food product in
which the genetic material (DNA) has been either destroyed or removed and
which has been shown to be "substantially equivalent" to the non-GE
variety, needs little in the form of health risk assessment and can be
marketed without labelling. Such a stance indicates that the main risks
that are perceived arise from the presence of "viable" DNA (intact genes)
and that if this is not present then all is well. The aim of this article
is to briefly analyse this notion from a basic genetics standpoint. We
shall see that this is an erroneous assumption since it ignores the real
dangers caused by disturbances in the host biochemistry which result as a
consequence of the genetic manipulation and which can persist in a product
regardless of the fact that the DNA may have been removed.
The real dangers of GE foods
DNA is a natural part of our diet being present in foods which either
retain or are derived from whole cells (fruits, vegetables, meat etc.).
This being the case it would be expected that we would also digest the DNA
from GE foods without any health problems. It would therefore appear that
the mere presence of genetic material in GE food only poses a danger in
certain special cases as, for example, where antibiotic resistance genes
persist in a product. However, the main hazards that result from the use of
genetic engineering in food production stem from the fact that (i) genetic
engineering brings about combinations of genes that would never occur
naturally and (ii), in the case of plants and animals, genetic engineering
is an imprecise technology resulting in the random incorporation of the new
genes into the host DNA. These two effects always combine to produce a
totally unpredictable disturbance in host genetic function as well as in
that of the introduced gene. The resulting disturbance in the biochemistry
of the host can unexpectedly produce novel toxins, allergens and reduced
nutritional value. Therefore, it is quite possible for a processed food in
which the DNA has been destroyed or removed to still possess potentially
harmful substances. A few examples will help to illustrate this point.
In the USA in 1989 a total of 5000 individuals became ill after consuming
an amino acid tryptophan health food supplement derived from GE bacteria.
Out of these, 37 died and 1500 became permanently disabled with sickness.
It is still debated as to whether the presence of the toxin was a direct
result of the genetic engineering or due to sloppy manufacturing
procedures. Nevertheless, if this product was produced today it would be
subject to health risk assessment since it is derived from a novel process;
that is, GE bacteria. Since this tryptophan was greater than 99% pure and
devoid of DNA, it would be passed as substantially equivalent to the same
substance obtained from non-engineered organisms. In other words if it was
marketed today, the same tragedy would result as the pre-clinical and
carefully monitored clinical type trials that are required to detect novel
toxins of the type that was produced would be seen as unnecessary and no
labelling would be required. It is also important to note that the
suspected novel toxin which caused all the problems was present at less
than 0.1% of the final product that went on sale. Interestingly, in 1996
the ACNFP approved the marketing of riboflavin (vitamin B2) derived from GE
bacteria with only contaminants present at greater than 0.1% being required
to be identified. Therefore, by these criteria the toxin present in the
tryptophan would not have attracted any attention or concern.
Many yeast strains are being engineered to have a higher metabolism and as
a result, enhanced fermentation properties in processes such as bread
baking and beer production. However, an investigation of GE yeast
containing extra copies of genes involved in the metabolism of glucose,
found that they also accumulate a highly toxic and mutagenic substance
known as methylglyoxal. The authors of this study warn that careful thought
should be given to the nature and safety of metabolic products when GE
yeast are used in food-related fermentation processes especially since
current risk assessments based upon the principle of substantial
equivalence are unlikely to detect any harmful substances.
A number of oil seed crops (especially oilseed rape), are being engineered
to have an altered oil composition for either "enhanced nutritional value"
or industrial use. GE oilseed rape, for example, with a high lauric acid
content is being grown in North America and is currently being reviewed by
the EU for cultivation in Europe. Oil from this crop will end up in a
diverse range of products such as soap and confectionery. In a research
study where a bacterial gene (6-esaturase) had been inserted into tobacco
plants, not only was the desired and nutritionally important
gamma-linolenic acid (GLA) produced but also octadecatetraenoic acid (OTA).
Although OTA is useful in a number of industrial processes (e.g. wax and
plastic manufacture), it is highly toxic.
A large percentage of the porcine and bovine growth hormone produced from
GE bacteria was found to possess an amino acid modification
(?-N-acetyllysine ), which not only rendered it useless but potentially
harmful if injected into pigs or cattle.
Finally, there is also one indirect health risk that arises from herbicide
and pest resistant GE crops which must be taken into account but which has
not adequately been addressed by the regulators. There is no data presented
as to the fate of the herbicide or pesticide within the plant. Does it
remain stable within the plant tissues? If it is degraded, what are the
products that are produced and what health risks do they pose? Higher
levels of herbicide are clearly expected to be present since Monsanto
applied (and was granted both in the USA and Europe), that the permitted
residual levels of Roundup in their Roundup Ready range of GE crops (soya,
maize, sugar beet, oilseed rape) be increased from 6mg to 20mg per kilogram
The inadequacy of substantial equivalence
These examples illustrate the fact that a product derived from a GE
organism (bacteria, yeast or plant), can be devoid of genetic material but
can still unexpectedly contain potentially harmful alterations to a GE
product, a novel toxin or elevated levels of a known hazardous substance.
The current systems for assessing the health risks of GE foods do not
appear to have fully taken into account this unpredictability of genetic
engineering technology. At present it is only required that the amounts of
a few known components (nutrients, allergens and natural toxins) be
measured in order for substantial equivalence to be established. When
viewed from a fundamental genetics standpoint, the manner in which the
principle of substantial equivalence is being applied would appear to be
conceptually flawed. Since genetic engineering has the potential to
unexpectedly produce novel toxins and allergens, the assessment of only
known constituents is insufficient.
This problem is further compounded by the fact that each analytical
technique that is used possesses it's own limitations. Unless one
fortuitously chose an analytical method that happened to detect a novel
compound in the GE food, it can quite easily be missed even if present in
abundance. As a result, since one cannot specifically test for an unknown
health hazard, it is clear that only by applying pharmacological-type
toxicity testing can the risks of GE foods be adequately assessed. If a new
drug is produced via genetically engineered organisms then it must quite
rightly go through pre-clinical tests in animals to assess acute toxicity
and, more importantly, extensive clinical trials in human volunteers to not
only determine efficacy, but also to detect any unexpected effects of the
product including unknown toxins resulting from the production process.
Given that the same imprecise technology is used to produce GE foods in
general then surely the same rules should apply for both. Clearly a double
standards situation exists which needs rectifying.
Pharmacological toxicity testing is designed to assess adverse effects of a
product in a very general manner regardless of whether it is a single
substance or a complex mixture and can therefore equally be applied to GE
foods as well as drugs.
Genetic Pollution. Antoniou, M. (1996) Nutritional Therapy Today 6 (4):
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Isolation of Escherichia coli synthesised recombinant eukaryotic proteins
that contain ?-N-acetyllysine. Violand BN et al. (1994) Protein Science 3:
Enhanced accumulation of toxic compounds in yeast cells having high
glycolytic activity: a case study on the safety of genetically engineered
yeast. Inose T and Kousaku M (1995) International Journal Food Science
Technology 30: 141-146.
Expression of a cyanobacterial ?6-desaturase gene results in ?-linolenic
acid production in transgenic plants. Reddy SA and Thomas TL (1996) Nature
Biotechnology 14: 639-642.
Nordlee JA et al. (1996) Identification of brazil-nut allergen in
transgenic soybeans. The New England Journal of Medicine 334: 688-692.
Report on Riboflavin Derived from Genetically Modified (GM) Bacillus
subtilis using Fermentation Technology. ACNFP Report 1996, Ministry of
Agriculture, Fisheries and Food Publications.
"Substantial Equivalence". Joint FAO/WHO Consultation in Rome, September
30th-October 4th, 1996.