1) What overarching scientific principles should be applied to the safety and nutritional assessment?
Experience throughout the world has led to the identification of a number of common scientific principles currently used in safety and nutritional assessment.
The existing food supply has a long history of safe use, even though some foods are not safe for some individuals and many foods contain substances that would present health concerns if they were present above accepted levels. Most foods derived using recombinant DNA techniques are obtained from traditional crops that have usually been modified to exhibit one or a few well-defined traits. The knowledge and experience gained in the use of traditional crops is an important component in the safety assessment of foods derived from such plants.
Safety assessment of whole foods and many complex food ingredients requires use of an approach that differs from the strategy used to assess safety of single, well-defined chemicals, such as food additives, pesticides and contaminants. The approach for whole foods is case-by-case, based on an evaluation of multi-disciplinary data and information, that is derived from, as appropriate, but is not limited to, agronomic, genetic, molecular biological, nutritional, toxicological and chemical properties. Toxicology testing in animals is not routinely employed, but when necessary based on an assessment of available data and information, tests should be designed to address specific issues.
The following issues are some of the main points considered in the evaluation: the new gene, the new protein and other food components, taking into account both intended and unintended changes in the food and steps to reduce the likelihood of adverse, unexpected effects. In specific cases, additional effects (such as antibiotic resistance) may be evaluated.
Genetically modified foods and conventional foods have many characteristics in common, and in many cases, the new food or food ingredient will be nutritionally equivalent to its conventional counterpart.
Analytical methods traditionally applied in the evaluation of food constituents such as total protein, fat, ash, fibre and micronutrients may need to be augmented with additional analyses using profiling methods to identify unexpected effects and modified nutrient profiles which may impact dietary intake and health.
Because of the potential for broad changes in nutrient levels and interactions with other nutrients as well as unexpected effects, it may be necessary in certain instances to undertake feeding tests in animals to determine outcomes that result from changes in nutrient profiles and nutrient bioavailability. Nutritional modifications which are within normal ranges of nutrient variation might require a less extensive evaluation than those outside normal ranges.
The data and information should be of a quality and quantity that would withstand scientific peer review. Safety assessment is designed to identify information on the nature and the severity of any hazards that may be present, allowing appropriate management methods to be defined.
In conclusion, safety assessment of food and food ingredients obtained using recombinant DNA techniques does not require new scientific principles or methodology. Similar principles for the assessment of the safety and wholesomeness of genetically modified foods should be applied as practised for conventional foods. Depending on the characteristics of the genetic modifications, specific safety and nutritional aspects are assessed.
2) What is the role, and what are the limitations, of substantial equivalence in the safety and nutritional assessment? Are there alternative strategies to substantial equivalence that should be used for the safety and nutritional assessment?
The concept of substantial equivalence is well established as an important component in safety assessment, and has been elaborated in several international reports. It is based on the idea that an existing organism (plant) used as food, or as a source of food, can serve as the basis for comparison when assessing the safety for human consumption of a food or a food component that has been modified or is new. There is a broad consensus that substantial equivalence is of value in safety assessment.
Application of the concept of substantial equivalence may lead to the identification of similarities and defined differences in the food and food ingredients. Further safety assessment will be focused on establishing the safety of the differences in the new product such that safety of the food or food ingredient can be established, relative to its comparator. The safety assessment carried out in this way does not provide an absolute safety warrant for the new product.
Another aspect of the concept of substantial equivalence is that it can only be applied where there is a suitable comparator. This requires that sufficient data is available or can be generated for the comparator. Where there is no comparator, substantial equivalence cannot be used to assess safety. In such cases, safety testing will be required based on the properties of the food concerned.
Current strategies for assessing the safety of foods derived from genetically modified plants are considered appropriate. There are presently no alternative strategies that would provide a better assurance of safety for genetically modified foods than the appropriate use of the concept of substantial equivalence. However, some aspects of the steps in safety assessment process could be refined to keep abreast of developments in genetic modification technology. Methodologies, such as profiling techniques, offer a means of providing a more detailed analytical comparison. However, much more developmental work would be necessary before such methods could be validated.
3) What scientific approach can be used to monitor and assess possible long-term health effects or unintended/unexpected adverse effects?
The Consultation considered that the methodologies for safety evaluation elaborated in the report are adequate to detect and evaluate any possible long-term effects of genetically modified foods.
The Consultation considered the issue of long-term effects from the consumption of genetically modified foods and noted that very little is known about the potential long-term effects of any foods. In many cases, this is further confounded by wide genetic variability in the population, such that some individuals may have a greater predisposition to food-related effects.
Against this background, the Consultation acknowledged that for genetically modified foods, the pre-marketing safety assessment already gives assurance that the food is as safe as its conventional counterpart. Accordingly it was considered that the possibility of long-term effects being specifically attributable to genetically modified foods would be highly unlikely.
An important aspect of the safety assessment is a consideration of the nature of the introduced gene product. Where there is no history of consumption of the introduced gene product or of the food, a 90-day study will probably be indicated. If such studies show evidence suggesting possible long-term effects, e.g. evidence of cell proliferation, further long-term studies would need to be considered if the development of the product was to continue.
The Consultation was of the view that monitoring to establish links between diet and disease is desirable. However, many chronic health effects are multifactorial and it was recognised that observational epidemiological studies would be unlikely to identify any such effects against a background of undesirable effects of conventional foods. Experimental studies, such as randomised controlled trials (RCTs), if properly designed and conducted, could be used to investigate the medium/long term effects of any foods, including genetically modified foods. Such studies could provide additional evidence for human safety, but would be difficult to conduct. In this respect, it is also important to recognise the wide variation in diets from day to day and year to year.
The same problems apply to the detection of potential long-term beneficial health effects. Nevertheless, it was recognised that genetically modified foods intended to produce nutritional effects are under development for use in developed and developing countries. In such cases, a change in nutrient levels in a particular crop plant may impact overall dietary intake and it would be important to monitor changes in nutrient levels in such foods and evaluate their potential effect on nutritional and health status.
The potential occurrence of unintended effects is not specific for the application of recombinant DNA techniques, rather it is an inherent and general phenomenon in conventional breeding. One of the approaches to cope with this problem is to select and discard plants with unusual and undesired phenotypic and agronomic parameters already at an early stage. The practice of consecutive back-crossing is also a major procedure used to eliminate unintended effects. Only in rare cases are these approaches accompanied by analytical screening of defined constituents.
Unintended effects due to genetic modification may be subdivided into two groups: those which are "predictable" based on metabolic connections to the intended effect or knowledge of the site of insertion and those which are “unexpected”. Due to the increased precision of genetic modification compared to conventional breeding, it may become easier to predict pathways likely to be influenced by unintended effects.
The comparator used to detect unintended effects should ideally be the near isogenic parental line grown under identical conditions. In practice, this may not be feasible at all times, in which case a line as close as possible should be chosen. The resulting natural variation should be taken into account in assessing the statistical significance of the unintended effect.
Where statistically significant unintended differences are observed, their biological significance should be assessed. This may be assisted by knowledge of the mechanisms leading to the changes. In order to assess the biological and safety relevance of an unintended effect, data on the genetically modified plant should be compared to data on other conventional varieties and literature data. If the differences exceed natural variations in traditional food crops, further assessment is required.
Present approaches to assess possible unintended effects are based, in part, on the analysis of specific components (targeted approach). In order to increase the probability of detecting unintended effects, profiling techniques are considered as useful alternatives (non-targeted approach). Profiling techniques are used at different level e.g. genomics, proteomics and metabolomics.
In the future, genetic modifications of plants are likely to be more complex perhaps involving multiple between-species transfers and this may lead to an increased chance of unintended effects. In such cases, profiling techniques may contribute to the detection of differences in a more extensive way than targeted chemical analysis but they are not yet fully developed and have certain limitations. Having detected differences using profiling techniques, their safety implications of such difficulties will still need to be considered.
4) What scientific approach can be used to assess the potential allergenicity?
An assessment of the potential allergenicity should be made for all genetically modified foods. In the assessment, the novel proteins resulting from the inserted gene should be the focus of the investigation in most cases.
An assessment of the potential allergenicity of the genetically modified food should be conducted in all cases. Possible enhancement of the inherent allergenicity of the host plant food should also be included in the assessment only when the intended effect of the genetic modification involves a significant alteration of the protein content of the food product derived from the host plant.
A decision-tree strategy should be applied in the assessment of the potential allergenicity of the novel protein(s). When the transferred gene is obtained from a source with a known history of allergenicity, the assessment should focus initially upon the immunochemical reactivity of the newly introduced protein with IgE from the blood serum of individuals with known allergies to the source of the transferred genetic material. Where necessary (in cases where no evidence of immunochemical reactivity is obtained), skin tests with extracts of the novel protein and blinded oral food challenges with the genetically modified food should be conducted on individuals with known allergies to the source of the transferred genetic material to provide confirmation that the novel protein is not allergenic. This series of tests provides adequate evidence regarding the allergenicity (or lack thereof) of novel proteins expressed by genes obtained from known allergenic sources.
The decision-tree approach should rely upon various criteria used in combination (since no single criterion is sufficiently predictive). The current criteria include the sequence homology of the newly introduced protein to known allergens, the immunochemical reactivity of the newly introduced protein with IgE from blood serum of appropriate, allergic individuals when sequence homology is found, and the stability of the novel protein to digestion in gastric and intestinal model systems. This Consultation suggests that the incorporation of two additional criteria to the decision-tree approach when the genetic material is not known to be allergenic might be useful. The level and site of expression of the novel protein and the functional properties of the novel protein should be considered for addition to the list. These criteria taken together offer reasonable evidence that the novel protein is not allergenic, is not cross-reactive with known allergens, and has limited potential to become a food allergen. However, the development of additional criteria could offer additional confidence in the decision-tree approach. In particular, this Consultation advocated continued research on the development of a well-validated animal models for the assessment of the potential allergenicity of novel proteins from genetically modified foods. The Consultation also advocated additional research to identify allergenic proteins in food and to determine their protein sequences.
5) What scientific approach can be used to assess the possible risks arising from the use of antibiotic resistance marker genes in plants and microorganisms?
In genetically modified plants, the product of an antibiotic resistance gene must be subjected to standard safety assessments as would be performed on any other introduced gene product. Thus the product of the antibiotic resistance gene must be assessed for toxicity and potential allergenicity.
Where antibiotic resistance marker genes are present in plants or microorganisms, the possibility of transfer of the genes to pathogenic microorganisms and possible clinical implications must be considered. Horizontal gene transfer from plants and plant products consumed as food to gut microorganisms or human cells is considered as a rare possibility, but cannot be completely discounted. The most important consideration with respect to horizontal gene transfer is the consequence of a gene being transferred and expressed in transformed cells. An important example is the transfer of antimicrobial resistance genes, if it were to occur, from genetically modified foods to gut microorganisms. Important considerations for the assessment of the consequences of the transfer and expression of this gene in transformed cells would be the clinical and veterinary importance of the antibiotic in question, the levels of natural resistance and the availability of effective alternative therapies. In general, antibiotic resistance genes used in food production that encode resistance to clinically important antibiotics should not be present in widely disseminated genetically modified organism or foods and food ingredients.
FAO: http://www.fao.org/WAICENT/FAOINFO/ECONOMIC/ESN/biotech.htm
