Question: How can we tell if something we buy in the shops has been genetically modified or not?

Ricarda Steinbrecher answered on 26 Jun 2012:

In the EU – thus also the UK – labelling of food is required if any of its ingredients has a GM presence above 0.9 per cent. This ingredient needs to be identified as GM on the label. So anything GM present below 0.9 per cent does not require labelling, though the technical capacity to measure and identify the presence of a GM contaminant is far below 0.9 and can be as little as 0.01 or even 0.001 per cent. Thus the labelling is not 100 per cent accurate.

So far GM contamination of 0.9 per cent in food intended for human consumption is only allowed if the presence of the GM contaminant is accidental and if the GM compound has been identified as being of an authorised identity. For example the accidental presence of a GM maize producing pharmaceutical compounds would not be acceptable.
This is currently under debate at the EU level, with suggestions to allow up to 0.9 per cent contamination for any GM contaminant, no matter whether previously approved for food consumption or not. This it is quite problematic, as ignoring the identity of the low level contaminant may compromise human health and also fails to properly inform the consumer.

There is presently no legal requirement to label products derived from animals that have been fed a GM diet, whether that is meat, milk, eggs or fish from aquaculture. Some supermarkets have a policy of not selling products derived from animals fed on GM.

Honey also requires labelling if it contains GM pollen or ingredients.

There is no labelling in the US or Canada, despite consumers requesting their governments to give them the right to choose.

There are arguments though that the right to choose in itself is insufficient, as it actually allows for contamination and unsustainable agriculture. In Canada for example GM contamination of oilseed rape is so high, that the production of GM-free oilseed rape (there called canola) is no longer possible, including of course organic production to the detriment of organic farmers – and consumers who want the choice of GM free. Labelling cannot prevent this, but only document it.

If you want to be able to identify GM products / foods without having to resort to labels – there is little chance to be able to do so with the naked eye. This has actually been identified as a real problem, as GM and non-GM most of the time look just like each other from the outside and neither farmers nor consumers will be able to distinguish between them. So contamination can easily take place without noticing, including contamination by experimental crops or designs.