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The Safety of Genetically Modified Foods Produced through Biotechnology
Adopted by SOT September 25th, 2002
Executive Summary
The Society of Toxicology (SOT) is committed to protecting and enhancing human,
animal and environmental health through the sound application of
the fundamental principles of the science of toxicology. It is with
this goal in mind that the SOT defines here its current consensus
position on the safety of foods produced through biotechnology (genetic
engineering). These products are commonly termed genetically-modified
foods, but this is misleading since conventional methods of microbial,
crop and animal improvement also produce genetic modifications and
these are not addressed here.
- The available scientific evidence indicates that the potential adverse health
effects arising from biotechnology-derived foods are not different
in nature from those created by conventional breeding practices
for plant, animal, or microbial enhancement, and are already familiar
to toxicologists. It is therefore important to recognize that it
is the food product itself, rather than the process through which
it is made, that should be the focus of attention in assessing safety.
- We support the use of the substantial equivalence concept as part of the safety
assessment of biotechnology-derived foods. This process establishes
whether the new plant or animal is significantly different from
comparable non-engineered plants or animals used to produce food
that is generally considered to be safe for consumers. It provides
critical guidance as to the nature of any increased health hazards
in the new food. To establish substantial equivalence, extensive
comparative studies of the chemical composition, nutritional quality,
and levels of potentially toxic components in both the engineered
and conventional crop or animal are conducted. Notable differences
between the existing and new organism would require further evaluation
to determine whether the engineered form presents a higher level
of risk. Through this approach, the safety of current biotechnology-derived
foods can be compared with that of their conventional counterparts
using established and accepted methods of analytical, nutritional
and toxicological research.
- Studies of this type have established that the level of safety to consumers
of current genetically engineered foods is likely to be equivalent
to that of traditional foods. At present, no verifiable evidence
of adverse health effects of BD foods has been reported, although
the current passive reporting system probably would not detect minor
or rare adverse effects or a moderate increase in effects with a
high background incidence such as diarrhea.
- The changes in the composition of existing foods produced through biotechnology
are quite limited. Assessing safety may be more difficult in the
future if genetic engineering projects cause more substantial and
complex changes in a foodstuff. Methods have not yet been developed
with which whole foods (in contrast to single chemical components)
can be fully evaluated for safety. Progress also needs to be made
in developing definitive methods for the identification and characterization
of proteins that are potential allergens and this is currently a
major focus of research. Improved methods of profiling plant and
microbial metabolites, proteins and gene expression may be helpful
in detecting unexpected changes in BD organisms and in establishing
substantial equivalence. A continuing evolution of toxicological
methodologies and regulatory strategies will be necessary to ensure
that the present level of safety of biotechnology-derived foods
is maintained in the future.
Introduction
The Society of Toxicology (SOT) is committed to protecting and enhancing human,
animal and environmental health through the sound application of
the fundamental principles of the science of toxicology. It is with
this goal in mind that the SOT defines here its current consensus
position on the safety of foods produced through biotechnology.
In this context, biotechnology is taken to mean those processes
whereby genes that are not endogenous to the organism (transgenes)
are transferred to microorganisms, plants or animals employed in
food production, or where the expression of existing genes is permanently
modified, using the techniques of genetic engineering. We intentionally
avoid using the term genetically modified organisms (GMOs) or foods
in this context since conventional techniques of plant and animal
breeding, which are not considered here, also involve genetic modification.
The extent of the genetic changes resulting from such conventional
breeding techniques, which is generally undefined, far exceeds that
typically produced by transgenic methods. Consequently, it is important
to recognize that it is the product, and not the process of modification,
that is the focus of concern regarding the human or environmental
safety of biotechnology-derived (BD) foods.
The principal
responsibilities of toxicologists are to define and characterize
the potential for natural and manufactured materials to cause adverse
health effects and to assess, as accurately as possible, the plausibility
and level of risk for human or animal health or for environmental
damage under a defined set of circumstances. It is not the task
of the Society of Toxicology to determine the overall value of a
product or process by balancing health or environmental risks with
potential benefits, or to choose between different strategies to
manage risk, although toxicological considerations are important
in both processes. Our purpose here is rather to identify and consider
the primary toxicological issues associated with BD foods. Major
areas of concern in the development and application of such foods
in agriculture relate to the possibility of deleterious effects
on both human health and the environment. We do not consider here
some aspects of the possible environmental impact of GM organisms
such as gene transfer to non-engineered plants.
Types of Toxicological Hazards to Consumers and Producers Associated
with BD Foods
Current techniques of developing organisms used in the production of BD foods typically
involve the transfer to the host of the desired gene or genes in
combination with a promoter and a gene for a selectable marker trait
that allows the efficient isolation of cells or organisms that have
been transformed from those that have not. Common selectable markers
in plants have included resistance to antibiotics (kanamycin/neomycin
or ampicillin) or herbicides.
Several key issues have been raised with respect to the potential toxicity associated
with BD foods, including the inherent toxicity of the transgenes
and their products, and unintended (pleiotropic or mutagenic) effects
resulting from the insertion of the new genetic material into the
host genome. Unintended effects of gene insertion might include
an over-expression by the host of inherently toxic or pharmacologically-active
substances, silencing of normal host genes, or alterations in host
metabolic pathways. It is important to recognize that, with the
exception of the introduction of marker genes, the process of genetic
engineering does not, in itself, create new types of risk. Most
of the hazards listed above are also inherent in conventional breeding
methods.
The Concept of Substantial Equivalence
The guiding principle in the evaluation of BD foods by regulatory agencies in
Europe and the United States is that their human and environmental safety
is most effectively considered relative to comparable products and
processes currently in use. From this arises the concept of “substantial
equivalence.” If a new food is found to be substantially equivalent
in composition and nutritional characteristics to an existing food,
it can be regarded as being as safe as the conventional food (US FDA,
1992; OECD, 1993; Maryanski, 1995; Kuiper et al., 2001) and
does not require extensive safety testing. Evaluation of substantial
equivalence includes consideration of the characteristics of the
transgene and its likely effects within the host, and measurements
of protein, fat and starch content, amino acid composition and vitamin
and mineral equivalency together with levels of known allergens
and other potentially toxic components. BD foods can either be substantially
equivalent to an existing counterpart, substantially equivalent
except for certain defined differences (on which further safety
assessments would then focus), or be non-equivalent, which would
mean that more extensive safety testing might be necessary. The
examination of substantial equivalence therefore may only be the
starting point of the safety assessment. It provides a valuable
guide to the definition of potential hazards from BD foods and illuminates
necessary areas for further study (FAO/WHO, 2000). While there is
some concern relative to the meaning of “substantial”
and how equivalency should be established, and debate over its use
continues (e.g. see Millstone et al., 1999 and following
correspondence; Royal Society of Canada, 2001; Kuiper et al.,
2001), the concept appears to be logical and robust in assessing
the safety of foods derived from both genetically-modified plants
and microorganisms (FAO/WHO, 2000; 2001a). If it can be established
with reasonable certainty that a BD food is no less safe than its
conventional counterpoint, it provides a standard likely to be satisfactorily
protective of public health. It is also an approach that has the
flexibility to evolve in concert with the field of transgenic technology.
A recent study of US FDA procedures for assessing the safety of BD
foods by the US General Accounting Office reviews these procedures
and concludes that the current regimen of safety tests are adequate
to assess existing BD foods (US General Accounting Office, 2002).
Key issues with respect to human health effects of BD Foods
Is the
transgene itself toxic? Can it be transferred to the genome of a
consumer?
Humans typically consume a minimum of 0.1 to 1 gram of DNA in their diet each day
(Doerfler, 2000). Therefore, the transgene in a genetically engineered
plant is not a new type of material to our digestive systems and
it is present in extremely small amounts. In transgenic corn, the
transgenes represent about 0.0001% of the total DNA (Lemaux and
Frey, 2002). Decades of research indicate that dietary DNA has no
direct toxicity itself. On the contrary, exogenous nucleotides have
been shown to play important beneficial roles in gut function and
the immune system (Carver, 1999). Likewise, there is no compelling
evidence for the incorporation and expression of plant-derived DNA,
whether a transgene or not, into the genomes of consuming organisms.
Defense processes have evolved, including extensive hydrolytic breakdown
of the DNA during digestion, excision of integrated foreign DNA
from the host genome, and silencing of foreign gene expression by
targeted DNA methylation that prevent the incorporation or expression
of foreign DNA (Doerfler, 1991; 2000). Although much remains to
be learned about the fate of dietary DNA in mammalian systems (Doerfler,
2000), the possibility of adverse effects arising from the presence
of transgenic DNA in foods either by direct toxicity or gene transfer
is minimal (FAO/WHO, 2000; Royal Society, 2002). Does the product encoded by the transgene present a risk to consumers or
handlers?
The potential toxicity of the transgene product must be considered on a case-by-case
basis. Particular attention must be paid if the transgene produces
a known toxin (such as the Bacillus thuringiensis (Bt) endotoxins)
or a protein with allergenic properties.
Production of toxins
The level of risk of these gene products to consumers and those
involved in food production can be and is evaluated by standard
toxicological methods. The toxicology testing for the Bt endotoxins
typifies this approach and has been described in detail by US EPA
(US EPA, 1998; 2001). The safety of most Bt toxins is assured by
their easy digestibility as well as by their lack of intrinsic activity
in mammalian systems (Betz et al., 2000; Siegel, 2001; Kuiper
et al., 2001). In this case, the good understanding of the
mechanism of action of Bt toxins, and the selective nature of their
biochemical effects on insect systems, increases the degree of certainty
of the safety evaluations. However, each new transgenic product
must be considered individually based on exposure levels and its
potency in causing any toxic effects, as is typical of current risk
assessment paradigms for chemical agents. Production of allergens
Allergenicity is one of the major concerns about food derived from
transgenic crops. However, it is important to keep in mind that
eating conventional food is not risk-free; allergies occur with
many known and even new conventional foods. For example, the kiwi
fruit was introduced into the US and the European market in the
1960’s with no known human allergies; however, today there are people
allergic to this fruit (Pastorello et al., 1998).
The issues that have to be addressed regarding the potential allergenicity of BD
foods are:
-
do the products of novel genes have the ability to elicit allergic reactions
in individuals who are already sensitized to the same, or a
structurally similar, protein?
-
will transgenic techniques alter the level of expression of existing protein
allergens in the host crop plant?
-
do the products of novel genes engineered into food plants have the ability
to induce de novo sensitization among susceptible individuals?
Considerable scientific resources are being committed to determine the most appropriate
and accurate approaches for identifying and characterizing potentially
allergenic proteins. The first systematic approach to allergenicity
assessment was developed by the International Life Sciences Institute
(ILSI) in collaboration with the International Food Biotechnology
Council and published in 1996 (Metcalfe et al., 1996). The
hierarchical approach described therein has been reviewed and revised
by the World Health Organization (WHO) and the Food and Agriculture
Organization of the United Nations (FAO) (FAO/WHO, 2001b). The main
approaches currently used in the evaluation of allergenicity are:
Determinations of structural similarity, sequence homology and serological identity:
The objective is to determine whether, and to what extent, the novel
protein of interest resembles other proteins that are known to cause
allergy among human populations. There are essentially three generic
approaches. The first is to examine the overall structural similarity
between the protein of interest and known allergens. The second
is to determine, using appropriate databases, whether the novel
protein is similar to known allergens with respect to either overall
amino acid homology, or with respect to discrete areas of the molecule
where complete sequence identity with a known allergen may indicate
the presence of shared epitopes. The third approach is to determine
whether specific IgE antibodies in serum drawn from sensitized subjects
are able to recognize the protein of interest. Assessment of proteolytic stability: There exists a good, but incomplete,
correlation between the resistance of proteins to proteolytic digestion
and their allergenic potential, the theory being that relative resistance
to digestion will facilitate induction of allergic responses provided
the protein possesses allergenic properties (Astwood et al.,
1996). One approach therefore is to characterize the susceptibility
of the protein of interest to digestion by pepsin or in a simulated
gastric fluid. However, this approach alone may not be sufficient
to identify cross-reactive proteins with the potential to elicit
allergic responses in food- or latex-sensitized individuals as in
the case of oral allergy syndrome or latex-fruit syndrome (Yagami
et al., 2000). Nor are considerations of stability to digestion
necessarily relevant for allergens that act through dermal or inhalation
exposure and that may have significance for worker health. In these
cases, other approaches such as structural homology searches and
the use of animal models may be effective in identifying potential
new allergens. Use of animal models: Currently there are available no widely accepted
or thoroughly evaluated animal models for the identification of
protein allergens. Nevertheless, progress is being made and methods
based on the characterization of allergic responses or allergic
reactions in rodents and other species have been described (Kimber
and Dearman, 2001).
Although testing strategies for allergens are still evolving and no single test is
fully predictive of human responses, the approaches outlined above,
when used in combination, allow scientists to address questions
of potential allergenicity and these will increase in precision
and certainty with time. Considerations of this type led the US
federal agencies to deny approval of StarLink corn for human consumption
because of the possibility that its Bt protein, Cry9C, may be a
human allergen. This protein had been modified to slow its digestion
and prolong its effect in the insect gut and this change rendered
the protein less digestible in the human gut as well. After the
accidental introduction of StarLink corn into the human food chain,
a limited number of illnesses among consumers were reported. These
were investigated by the Centers for Disease Control who found no
evidence that the corn products were responsible (CDC, 2001). However,
although this study is reassuring, methodological limitations make
it less than conclusive (Kuiper et al., 2001), and it cannot
eliminate the possibility that some adverse effects may have occurred
that were not reported. Because of this incident, StarLink corn
is no longer marketed. With the exception of Cry9C, none of the
engineered proteins in foods so far evaluated through the FDA consultation
process has had the characteristics of an allergen.
The only documented case where a human allergen was introduced into a food component
by genetic engineering occurred when attempts were made to improve
the nutritional quality of soybeans using a Brazil nut protein,
the methionine-rich 2S albumin. Allergies to the Brazil nut have
been documented (Arshad et al., 1991), and while still in
precommercial development, testing of these new soybeans for allergenicity
was conducted in university and industrial laboratories. It was
found that serum from people allergic to Brazil nuts also reacted
to the new soybean (Nordlee et al., 1996). Once this was
discovered, further development of the new soybean variety was halted
and it was never marketed. This work led to the identification of
the major protein associated with Brazil nut allergy which was previously
unknown (Nordlee et al., 1996). Will insertion of the transgene increase the potential hazard from toxins or pharmacologically
active substances present in the host?
Concern has been expressed about the randomness with which genes are inserted
into the host by current genetic engineering processes. This could,
and does, result in pleiotropic and insertional mutagenic effects.
The former term refers to the situation where a single gene causes
multiple changes in the host phenotype and the latter to the situation
where the insertion of the new gene induces changes in the expression
of other genes. Such changes due to random insertion might cause
the silencing of genes, changes in their level of expression or,
potentially, the turning on of existing genes that were not previously
being expressed. Pleiotropic effects could be manifested as unexpected
new metabolic reactions arising from the activity of the inserted
gene product on existing substrates or as changes in flow rates
through normal metabolic pathways (Conner and Jacobs, 1999).
Unexpected and potentially undesirable pleiotropic or mutagenic changes in the
genome of the host do occur (e.g. see a recent listing by Kuiper
et al., 2001), but these would likely be revealed by their
effects on the development, growth or fertility of the host, or
by the extensive testing of its chemical composition compared with
isogenic untransformed plants which is a necessary part of any safety
evaluation of transgenic crops.
In the United States, since 1987, the USDA Animal and Plant Health Inspection Service has completed
over 5000 field trials with more than 70 different transgenic plant
species. The only unexpected result was a mutation in a color gene
and gene silencing through changes in the methylation status of
these genes that led to unexpected color patterns in petunia flowers.
Both of these effects are also seen in conventional plant breeding
(Meyer et al., 1992). While the possibility of an undetected
increase in a toxic component in a new food cannot be entirely eliminated,
the current safeguards make this unlikely and no toxicologically
or nutritionally significant changes of this type are evident in
the transgenic plants so far marketed for food production.
Substantial public concern about the safety of BD products was raised in 1989
when a number of cases of eosinophilia-myalgia syndrome (EMS) were
reported among users of the amino acid tryptophan as a dietary supplement.
By mid-1993, 37 deaths had been attributed to this outbreak (Mayeno
and Gleich, 1994). The development of the syndrome appeared among
users of some batches of the supplement after a change in the manufacturing
process that included the use of a new genetically modified microorganism
in the fermentation. However, concomitant with this change were
additional alterations in certain filtration and purification steps
used previously in the manufacturing process. The exact cause of
the outbreak and the nature of the toxic impurity have not been
established with certainty. Thus, it is not possible to determine
whether the change in purification, the genetic engineering of the
organism, or some other factor or factors were to blame (Mayeno
and Gleich, 1994). A subsequent investigation revealed that cases
of EMS occurred among consumers of tryptophan before the GM organism
was introduced into the manufacturing process, although at a lower
incidence. Thus, the genetic modifications might have caused an
increase in the level of the agent which was responsible for tryptophan-associated
EMS, but it did not create a novel toxicant (Sullivan et al.,
1996). This event is troubling in that the tryptophan would be regarded
as highly purified (99.6% or higher) and no adequate animal model
has been found to replicate EMS, a probable autoimmune disease.
This illustrates that toxicology has limits in its ability to explain
and predict adverse effects in humans.
These examples indicate that careful analysis of the changes in BD organisms is
necessary to ensure against unexpected alterations in the levels
of toxins, allergens and essential nutrients. This will be particularly
critical if, as seems likely, engineering of the synthetic pathways
of secondary metabolites is undertaken in plants e.g. to increase
their resistance to insects and pathogens or produce compounds of
pharmaceutical value. Such changes might create new and unanticipated
secondary compounds with unknown toxic properties. New approaches
to profiling changes in metabolites, proteins, and gene expression
(Kuiper et al., 2001) may be helpful in such cases. Does the possible transfer of antibiotic resistance marker genes from the
ingested BD food to gut microbes present a significant human hazard?
The development of antibiotic resistance among pathogenic bacteria is a
significant human health issue. However, no contribution to antibiotic
resistance in gut bacteria arising from antibiotic resistance markers
in BD foods has been documented. For several reasons, including
the efficient destruction of the resistance gene in the human gut
and the very low intrinsic rate of plant-microbe gene transfer,
any contribution from this source is expected to be extremely small
(Royal Society, 1998). Genes for resistance to kanamycin and related
antibiotics already occur quite commonly in the environment including
the flora of the human gut which naturally contains about 1 trillion
(1012) kanamycin- or neomycin-resistant bacteria
(Flavell et al., 1992). Even if the occasional transfer of
resistance from plant to bacterium did occur, the practical impact
would be negligible. However, since any increase in antibiotic resistance
is recognized as undesirable, and the technology is now available
to omit the use of such marker genes, future genetically-modified
organisms are unlikely to contain them (e.g. see Goldsbrough et
al., 1996; Koprek et al., 2000). Thus concerns related
to their use are likely to diminish. Will genetic transformation adversely affect the nutritional value of the host?
In the United States, the US FDA is entrusted with assuring that the nutritional composition
of BD foods is substantially equivalent to that of the nonmodified
food. Studies are performed to determine whether nutrients, vitamins
and minerals in the new food occur at the same level as in the conventionally-bred
food sources (e.g. see Berberich et al.,1996; Sidhu et
al., 2000). A typical example is the case of Roundup Ready soybeans.
In this case, the protein, oil, fiber, ash, carbohydrates and moisture
content and the amino acid and fatty acid composition in seeds and
toasted soybean meal were compared with conventional soybeans. Fatty
acid compositions and protein or amino acid levels of soybean oil
were compared and special attention was given to checking the levels
of antinutrients typically found in soybeans, e.g., trypsin inhibitors,
lectins and isoflavones (Padgette et al., 1996). One difference
between the conventional and non-conventional soybeans was detected
in defatted, nontoasted soybean meal, the starting material for
commercially utilized soybean protein which is not itself consumed.
In this material, trypsin inhibitor levels were 11–26% higher in
the transgenic soybeans. The levels of the trypsin inhibitors were
similar in all lines in the seeds and in defatted, toasted soybean
meal, the form used in foods. Except for this difference in trypsin
inhibitor levels, all other nutritional aspects were equivalent
between the transgenic line and the conventional soybean cultivars.
Feeding studies demonstrated that there were no evident differences
in nutritional value between the conventional and transgenic soybeans
in rats, chickens, catfish and dairy cattle (Hammond et al.,
1996). Domestic animal feeding studies with a number of other transgenic
crops (e.g. see Kuiper et al., 2001) have similarly shown
no significant adverse changes in nutritional value. Will the transgene product adversely affect nontarget organisms?
In addition to the general concerns addressed that relate to food safety, additional
attention is needed when the gene product is pesticidal or otherwise
may be toxic to nontarget organisms that consume it. The effects
of each transgene product that is designed for pesticidal effects
must be evaluated on a case-by-case basis against target and nontarget
organisms under specific field growth conditions for each transgenic
crop. The foremost current example of this is the incorporation
of Bt genes into crop plants for insect control. The toxic properties
of Bt endotoxins to both target and nontarget species of many kinds
are well known (Betz et al., 2000). They show a narrow range
of toxicity limited to specific groups of insects, primarily Lepidoptera,
Coleoptera or Diptera, depending on the Bt strain. Nevertheless,
Bt-producing plants have been tested broadly to determine whether
any alteration in this limited spectrum of toxicity has occurred,
without the discovery of any unexpected results (see Orr and Landis,
1997; Pilcher et al., 1997; Lozzia et al., 1998; Gatehouse
et al., 2002 for examples of such studies). Exotoxins and
enterotoxins, which are much more broadly toxic than the endotoxins,
are also produced by some Bt strains, but these are not present
in the transformed plant because their genes are not transferred
into the crop.
In plants transformed
with Bt genes to control lepidopterans, toxicity to nontarget lepidopterans
would be expected if exposure occurs by feeding on the transformed
crop. Particular concern has been expressed over the potential toxicity
of the Bt toxin in corn pollen to the Monarch butterfly after initial
laboratory studies showed increased mortality in larvae fed on leaves
dusted with transgenic pollen (Losey et al., 1999). However,
most transgenic corn pollen contains much lower, nonlethal levels
of Bt toxins than the strain used in this study and there is only
a limited synchrony between the feeding period of the most sensitive
younger larvae and the period when corn pollen is shed. Also, corn
pollen does not typically move far beyond the borders of the field,
leaving significant amounts of milkweed uncontaminated in many locations.
For these reasons, a detailed risk assessment concluded that it
is unlikely that a substantial risk to these butterflies exists
in the field since only a negligible portion of the population is
exposed to toxic levels of Bt (Sears et al., 2001; Gatehouse
et al., 2002). Beyond the question of the potential toxicity
of Bt corn to such valued insects, it is also important to recollect
that the common alternative is to spray corn with synthetic insecticides,
which are not as selective as the Bt toxin. In a sweet corn field
containing milkweed plants and treated with a synthetic pyrethroid
for insect control, 91–100% of the monarch butterfly larvae placed
on the milkweed leaves after spraying were killed. In plots where
Bt sweet corn was planted and the pollen fell naturally on the milkweed
leaves, larval death rates were much lower (7–20%) and indistinguishable
from those in untreated non-Bt corn plots (Stanley-Horn et al.,
2001).
Future Challenges in the Assessment of the Safety of BD Foods
Current safety assessment methodologies are focused primarily on the evaluation
of the toxicity of single chemicals. Food is a complex mixture of
many chemicals. Using animal models, the evaluation of most aspects
of the safety of single components of the diet, such as a Bt toxin,
is possible using widely accepted protocols. Future projects may
involve more complicated manipulations of plant chemistry. In this
case, safety testing will be more challenging. Whole foods cannot
be tested with the high dose strategy currently used for single
chemicals to increase the sensitivity in detecting toxic endpoints
(MacKenzie, 1999; Royal Society of Canada, 2001). Also, the question
of potential deleterious interactions between new, or enhanced levels
of known, toxic agents in BD foods will undoubtedly be raised. The
safety testing of multiple combinations of chemicals remains a difficult
proposition for toxicologists. In view of these challenges, there
is a clear need for the development of effective protocols to allow
the assessment of the safety of whole foods (NRC, 2000; Royal Society
of Canada, 2001).
Conclusions
The responsibility of toxicologists is to assess whether foods derived through biotechnology
are at least as safe as their conventional counterparts and to ascertain
that any levels of additional risk are clearly defined. In achieving
this goal, it is important to recognize that it is the food product
itself, rather than the process through which it is made that should
be the focus of attention. In assessing safety, the use of the substantial
equivalency concept provides guidance as to the nature of any new
hazards. Scientific analysis indicates that the process of BD food production is unlikely
to lead to hazards of a different nature than those already familiar
to toxicologists. The safety of current BD foods, compared with
their conventional counterparts, can be assessed with reasonable
certainty using established and accepted methods of analytical,
nutritional and toxicological research. A significant limitation may occur in the future if transgenic technology results
in more substantial and complex changes in a foodstuff. Methods
have not yet been developed by which whole foods (as compared with
single chemical components) can be fully evaluated for safety. Progress
also needs to be made in developing definitive methods for the identification
and characterization of protein allergens and this is currently
a major focus of research. Improved methods of profiling plant and
microbial metabolites, proteins and gene expression may be helpful
in detecting unexpected changes in BD organisms and in establishing
substantial equivalence. The level of safety of current BD foods to consumers appears to be equivalent
to that of traditional foods. Verified records of adverse health
effects are absent although the current passive reporting system
would probably not detect minor or rare adverse effects, nor can
it detect a moderate increase in common effects such as diarrhea.
However, this is no guarantee that all future genetic modifications
will have such apparently benign and predictable results. A continuing
evolution of toxicological methodologies and regulatory strategies
will be necessary to ensure that this level of safety is maintained.
References
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