In 1993 the Organisation for Economic Co-operation and Development (OECD) introduced the concept of substantial equivalence into the discussion of the safety evaluation of food from genetically modified organisms, a concept that has been agreed upon by many countries.

Substantial equivalence in this regard means that a genetically modified plant, or food derived therefrom, is equivalent to their conventional counterparts and can be treated in the same manner with respect to safety as their conventional counterparts.

Establishment of substantial equivalence is not a safety assessment in itself, but a dynamic, analytical exercise in the assessment of the safety of a new food relative to an existing food. The assessment of the safety of genetically modified organisms must address both intentional and unintentional effects that may result as a consequence of the genetic modification of the food source.

Products that are shown to be substantially equivalent to existing foods or food components: These products are regarded as being as safe as their counterpart and no further safety considerations other than those for the counterpart are necessary.

Examples: Genetically modified bakers yeast, oil from genetically modified oilseed rape

Products that are substantially equivalent to existing foods or food components except for defined differences: In these cases a further safety assessment should focus only on the defined differences. Typically, the defined differences will result from the intended effect of the introduction of genetic material that encodes for one or more proteins that may, or may not, modify endogenous components or produce new components in the host organism.

Examples: Genetically modified bakers yeast, Triticale (a wheat/rye cross)

Products that are not substantially equivalent to existing foods or food components: Up to now and probably for the near future, there have been few examples of foods or food components produced using genetic modification which could be considered to be not substantially equivalent to existing foods or food components. Nevertheless, it is conceivable that, with future developments in biotechnology, products could be developed which could be considered to have no conventional counterpart and for which substantial equivalent cannot be applied.

Examples: Carbohydrate polyesters, Kiwi fruit