Is GM Food Devoid of DNA Safe?

Dr Michael Antoniou, Senior Lecturer in Molecular Pathology, London, UK.

Biotechnology advisor 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

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

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

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-desaturase) 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 dry weight.

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):

Eosinophilia-myalgia syndrome and tryptophan production: a cautionary
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Isolation of Escherichia coli synthesized recombinant eukaryotic
proteins that contain ?-N-acetyllysine.
Violand BN et al. (1994) Protein Science 3: 1089-1097.

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.

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