What are the main issues of concern for human health?

While theoretical discussions have covered a broad range of aspects, the three main issues debated are tendencies to provoke allergic reaction (allergenicity), gene transfer and outcrossing.

Allergenicity. As a matter of principle, the transfer of genes from commonly allergenic foods is discouraged unless it can be demonstrated that the protein product of the transferred gene is not allergenic. While traditionally developed foods are not generally tested for allergenicity, protocols for tests for GM foods have been evaluated by the Food and Agriculture Organization of the United Nations (FAO) and WHO. No allergic effects have been found relative to GM foods currently on the market.

Gene transfer. Gene transfer from GM foods to cells of the body or to bacteria in the gastrointestinal tract would cause concern if the transferred genetic material adversely affects human health. This would be particularly relevant if antibiotic resistance genes, used in creating GMOs, were to be transferred. Although the probability of transfer is low, the use of technology without antibiotic resistance genes has been encouraged by a recent FAO/WHO expert panel.

Outcrossing. The movement of genes from GM plants into conventional crops or related species in the wild (referred to as “outcrossing”), as well as the mixing of crops derived from conventional seeds with those grown using GM crops, may have an indirect effect on food safety and food security. This risk is real, as was shown when traces of a maize type which was only approved for feed use appeared in maize products for human consumption in the United States of America. Several countries have adopted strategies to reduce mixing, including a clear separation of the fields within which GM crops and conventional crops are grown.

Feasibility and methods for post-marketing monitoring of GM food products, for the continued surveillance of the safety of GM food products, are under discussion.

GM labelling and the law

Since December 2002, the law in Australia states that food labels must show if food has been genetically modified or contains genetically modified ingredients, or whether GM additives or processing aids remain in the final food.

Special labels are not required for:

• ‘Highly refined’ foods where the altered DNA or protein is no longer in the food (for example, oil from modified corn).
• GM food additives or processing aids - unless the new DNA remains in the food to which it is added.
• GM flavours where less than 0.1 per cent is present in the food.
• Food, food ingredients or processing aids where GM ingredients are ‘unintentionally’ present in less than 1.0 per cent.
• Food that is prepared at the point of sale (so takeaway and restaurant food will not have to be labelled).

Labels may be required where:

• Genetic modification has altered the food so that its composition or nutritional value is ‘outside the normal range’ of similar non-GM goods; for example, if GM technology is used to add vitamins.
• Naturally occurring toxins are ‘significantly different’ to similar non-GM foods.
• The food produced using GM technology contains a ‘new factor’, which can cause allergic reactions in some people.
• Genetic modification raises ‘significant ethical, cultural and religious concerns’ regarding the origin of the genetic material used.

The risks of genetically modified crops

Food regulatory authorities require that GM foods receive individual pre-market safety assessments. Also, the principle of ‘substantial equivalence’ is used. This means that an existing food is compared with its genetically modified counterpart to find any differences between the existing food and the new product. The assessment investigates:

• Toxicity (using similar methods to those used for conventional foods)
• Tendency to provoke any allergic reaction
• Stability of the inserted gene
• Whether there is any nutritional deficit or change in the GM food
• Any other unintended effects of the gene insertion.

A GM food will only be approved for sale if it is safe and is as nutritious as its conventional counterparts. The safety of GM foods is still being debated, as it is impossible to predict all of the potential effects on human health and the environment. Some public health experts, however, advocate caution and believe that ‘we are only at the "scientific starting line", we simply don’t know whether GM foods are safe’. Stephen Leeder, ‘Genetically modified foods - food for thought’