GM Foods: Current tests are inadequate protection

We asked Michael Antoniou, molecular geneticist, to explain the dangers

SINCE its inception 20 years ago, genetic engineering or modification (GM) has spurred major advances in our understanding of how genes are organised in DNA. Genes are the inherited blueprints for the tens of thousands of proteins that act as the building blocks of the body for all forms of life from bacteria to humans. In the form of enzymes, proteins carry out all the biochemical processes, such as digestion of food, that keep us alive. Plants are made up from between 20,000 and 80,000 genes depending on their complexity. Estimates for animals, including humans, range from 80,000 to 150,000 genes.

Despite advances in our scientific knowledge, the gene "maps" for "higher" plants, animals and humans are still very incomplete, with only a few per cent of all genes known. More importantly, we know even less about how genes are switched on as an integrated whole to produce the correct combinations of proteins in the right place, time and quantity. What is clear is that genes and the proteins they make do not work in isolation but have evolved to exist and function in groups, the complexity of which we are only just beginning to appreciate. Nature has established boundaries so that reproduction can normally take place only between closely related forms. Tomatoes can cross-pollinate with tomatoes but not soya beans; cows can mate only with cows and not sheep. These same genes in their natural groupings have been finely tuned to work harmoniously together by millions of years of evolution.

It is claimed that GM in agriculture is a natural extension of traditional breeding methods, only more precise and safer. However, technically speaking, GM bears no resemblance to natural reproduction. The Government's Genetic Modification (Contained Use) Regulations define GM as "the altering of the genetic material in that organism in a way that does not occur naturally by mating or natural recombination or both".

GM allows the isolation and transfer of only one or a few genes (eg, herbicide or pest resistance) between totally unrelated organisms. This is contrary to the understanding that genes work in groups within a given form of life and not in isolation.

GM plants and animals start life in a laboratory where artificial units of foreign genetic material are randomly inserted into the host in a way which, to a lesser or greater degree, always disrupts natural genetic order and function. Furthermore, GM brings about combinations of genes that would never occur naturally. A gene from a common soil bacterium has been transferred to soya beans to make them resistant to a herbicide; anti-freeze protein genes from an arctic fish have been introduced into tomatoes and potatoes in an effort to confer resistance to frost.

The artificial nature of GM does not automatically make it dangerous. It is the imprecise way in which genes are combined and the unpredictability in how the foreign gene will behave in its new host that results in uncertainty. From a basic genetics perspective, GM possesses an unpredictable component that is far greater than the intended change. There would still appear to be so many unknowns that the risks to health and the environment are simply unquantifiable. A potential problem arising from herbicide-resistance GM crops that is largely being ignored is what is the fate of these chemicals within the plant? Are they stable? If they are degraded, what are the products that are produced? And what health risks do they pose?

Disruption in genetic function can lead to biochemical changes which in turn may give rise to novel toxins and allergies. In 1989 in the USA, consumption of the supplement L-tryptophan derived from GM bacteria killed 37 and rendered 1,500 permanently disabled. Many argue that this was due to sloppy manufacture.The scientists at the Japanese company concerned think otherwise and blame the GM process for producing traces of a potent new toxin.

Does our regulatory system protect us from these potential hazards? Health- risk assessment of GM foods compares only known components (eg, nutrients, known toxins and allergens) between GM and non-GM equivalent varieties. If things match up then all is assumed well. Short-term animal feeding trials are conducted in some cases. The fact that the L-tryptophan tragedy would repeat itself by these criteria highlights the inadequacy of this system. No tests with human volunteers are required for either toxicity or allergic reactions prior to marketing. Clearly the current regulatory process does not fully take into account the unpredictable side of GM. At the very least, long-term animal feeding trials followed by tests with human volunteers of the type required for GM drugs should be mandatory.