The principle of substantial equivalence

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It stems from a report of a working group established by the Organisation for Economic Co-operation and Development (OECD) of national experts to consider the safety implications of modern food biotechnology. The intention was to exchange ideas, data and information among experts to enhance international co-operation in this field. The working group considered numerous examples of how the safety of novel foods and food components had been evaluated in the past and established some concepts and principles that underpin the safety evaluation of foods derived by modern biotechnology. These principles have been widely accepted and are similar to recommendations made by other influential groups such as the World Health Organisation and the Food and Agriculture Organisation of the United Nations. The major conclusions of the OECD report are summarised below.

The report considered that the most practical method to establish food safety was to consider whether a novel food (or food component) was substantially equivalent to an analogous conventional food product, where one existed. Account should be taken of the processing (such as cooking) that the food may undergo, as well as how much food was to be consumed, by whom and the dietary pattern.

In demonstrating substantial equivalence, a number of factors have to be considered, such as:

• the characteristics and composition of the conventional food to which the new one is to be compared;
• knowledge of the component parts of the new product or organism, such as any introduced genes, the method used to introduce the new genetic material and how that new genetic material is expressed;
• the characteristics and composition of the new product or organism compared with the existing food or food component.

If the novel food is judged to be substantially equivalent to an existing food, then further safety or nutritional concerns are expected to be insignificant. Such foods are then treated in the same manner as their conventional counterparts. Where new classes of foods or food components are introduced it is more difficult to apply the concept of substantial equivalence. Here experience gained in the evaluation of similar materials is taken into account. Where a product is thought not to be substantially equivalent to an existing one, then further investigations, focusing on the identified differences are required. Totally new foods, where no similar materials have ever been consumed, must be evaluated solely on the basis of their own composition and properties.

Theoretical example: genetically-modified potatoes

As an example of the application of the principle of substantial equivalence, potatoes are an established part of the human diet. They can contain toxic alkaloids, but people generally know how to prepare them and avoid eating green potatoes which contain significant amounts of alkaloids. Potatoes are often infected by naturally-occurring viruses, but these do no harm to humans and have a long history of human consumption.

A potato that had been genetically-modified with one of these viruses so that it produced viral protein at levels comparable to those from naturally-infested potatoes would therefore be considered to be substantially equivalent to the infected potatoes that have a long history of safe use and consumption. This theoretical analysis applies only to viral proteins in the part of the potato plant that are traditionally consumed. It also assumes that the insertion of the viral coat protein gene does not lead to secondary effects through, for example, interruption of coding sequences within the plant’s genome.