‘Substantial Equivalence’ is a concept, which assumes that if GM food is similar to conventional food then it is safe because conventional food is safe.

‘Substantial Equivalence’ is not a testing procedure but a simple assessment procedure designed to make only the most basic comparisons between a GM food and a non-GM food. Only general biochemical, compositional analysis and the levels of known toxins or allergens are determined. For example, it might compare vitamin and amino acid levels between a GM tomato and a non-GM tomato - but other chemical differences which have resulted from the insertion of foreign genes into the plant and the GM transformation process in general would not be looked for. ‘Substantial Equivalence’ assessments aim to show that GM foods are ‘substantially equivalent’ to non-GM foods, and therefore ‘nothing new’.  

By virtually equating GM food with non-GM food the need to test GM products for their effects on human health, wildlife and the environment has effectively been removed.          

Example of how Substantial Equivalence Has Been Applied:

“GM glyphosate-tolerant soya beans (GTSBs) illustrate how the concept has been used in practice. The chemical composition of GTSBs is, of course, different from all antecedent varieties, otherwise they would not be patentable, and would not withstand the application of the herbicide glyphosate. It is quite straightforward to distinguish, in a laboratory, the particular biochemical characteristics that make them different. GTSBs have, nonetheless, been deemed to be substantially equivalent to non-GM soya beans by assuming that the known genetic and biochemical differences are toxicologically insignificant, and by focusing instead on a restricted set of compositional variables, such as the amounts of protein, carbohydrate, vitamins and minerals, amino acids, fatty acids, fibre, ash, isoflavones and lecithins. GTSBs have been deemed to be substantially equivalent because sufficient similarities appear for those selected variables.

“But this judgement is unreliable. Although we have known for about ten years that the application of glyphosate to soya beans significantly changes their chemical composition (for example, the level of phenolic compounds such as isoflavones), the GTSBs on which the compositional tests were conducted were grown without the application of glyphosate. This is despite the fact that commercial GTSB crops would always be treated with glyphosate to destroy surrounding weeds. The beans that were tested were, therefore, of a type that would never be consumed, while those that are being consumed were not evaluated. If the GTSBs had been treated with glyphosate before their composition was analysed, it would have been harder to sustain their claim to substantial equivalence. There is a debate in the research community on whether such changes to the chemical composition are desirable or undesirable, but it is an issue that remains unresolved, and which has been neglected by those who have deemed GTSBs and non-GM soya beans to be substantially equivalent.”

(A reference from an article by E. Millstone, E. Brunner and S. Mayer, ‘Beyond 'substantial equivalence'’, in Nature 401 (1999), pp. 525-526.)