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 Genetically engineered 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 Genetically engineered 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, Genetically engineered 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 Genetically Engineered 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 Genetically Engineered 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 Genetically Engineered 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. Genetically Engineered 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 Genetically Engineered 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 Genetically Engineered organism (bacteria, yeast or plant), can be devoid of genetic material but can still unexpectedly contain potentially harmful alterations to a Genetically Engineered product, a novel toxin or elevated levels of a known hazardous substance.
The current systems for assessing the health risks of Genetically engineered 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 Genetically Engineered 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 Genetically Engineered 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 Genetically Engineered 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 Genetically Engineered
foods as well as drugs.