Humans have always faced tricky safety problems with food because we eat plants, which are the most ingenious pesticide chemists on the planet. Plants produce an amazing panoply of chemicals to deter animals from eating them. We’ve responded biologically to this challenge by evolving chemical detoxification mechanisms in the liver.

Culturally, we’ve responded by inventing cooking and other food pre-treatments that allow us to eat dangerous foods, such as kidney beans, rapeseed oil and tapioca.

We even add spice to life by adding low quantities of plant poisons to recipes to improve flavour. And we breed our crop plants to reduce toxins. In short, “natural foods” are not necessarily safe and most of our crops are not as natural selection produced them.

Safety regime

Alpha/Flickr

Safety assessment of genetically engineered food (called GM or transgenic food) is yet another application of human ingenuity and the harnessing of past experience to obtain sustenance. It starts by careful comparison of the genetically-modified food (and any new components that are deliberately added to that food) against the safety record of existing dietary components for which we have a history of safe human consumption.

All new genetically engineered foods are assessed in a systematic way by food safety agencies (such as FSANZ in Australia), and detailed descriptions of these assessments appear on agency websites.

Assessments involve tests of proteins for toxicity in animal-feeding trials and tests for changes in the allergen content of the food. Scientists have completed numerous animal-feeding studies to ensure the safety of genetically-modified foods.

A comprehensive analysis of chemical composition is also carried out. The genetic stability of crop varieties is checked, as are the detailed structure of the DNA inserts. Extensive use of gene and protein databases enables better assessment of the chance of adverse outcomes.

Nagging doubts

Damon Lisch PLoS Biology Open Access License

But many people continue to worry about unexpected changes to food when it is genetically engineered. This concern has caught the attention of many scientists, whose response has been to evaluate the odds of unexpected adverse outcomes by comprehensive chemical and genetic surveys of crop varieties (chemical fingerprinting).

The good news from 44 different genetically-modified crops’ chemical fingerprinting studies (including work on maize, soybean, wheat and barley) is that the chance of unintended changes with transgenic crops is less than the risk of unintended changes occurring in new crop varieties created by conventional breeding.

These food fingerprinting investigations show the precise composition of a crop is readily affected by the position of the plant in the field in which it is being grown, climatic differences between farms, variation in soil chemistry and differences in crop composition generated by conventional breeding. These factors all produce more unexpected alteration of food composition than do the methods used to make GM food crops.

In a recent critical report by an anti-GM group, these major findings are not given adequate recognition. Indeed, one may reasonably ask why anti-GM reports should be given credence when they ignore well documented science from numerous independent laboratories.

Natural genetic engineering

A huge body of basic discoveries in genetics demonstrate that in nature and in farm fields, plant chromosomes are continually subjected to numerous DNA insertions and chromosome rearrangements that mimic the changes that occur when new DNA is introduced by genetic engineering.

These DNA changes come from a variety of processes, including radiation damage and the activities of numerous virus-like DNA parasites that are abundant in plant chromosomes. This frequent natural DNA scrambling is ignored by critics of GM technology.

John Innes Centre

One example of such “natural genetic engineering” was recently found in studies of an unusual (non-GM) orange tree variety growing in Sicily. This is a variety that produces blood-red oranges. The red fruit pigments are anthocyanin plant chemicals that are absent from the juice of conventional sweet oranges and may well have beneficial health properties.

Blood-orange varieties emerged several centuries ago as a natural mutation. We now know that this mutation occurred by insertion of a mobile genetic parasite near a key gene, called Ruby, whose activity is needed for successful red pigment formation. Ruby was turned on by the accidental insertion of parasitic DNA near her location in the chromosome.

This is the type of genetic manipulation that genetic engineers do in the lab but, in this case, a natural DNA parasite did it in a Sicilian orange grove.

Another example of natural genetic engineering was discovered in an Illinois soybean field in 1987, where a (non-GM) colour-mutated soybean flower appeared spontaneously in a field of soybeans.

This natural mutation was named wp. It’s interesting to crop-breeders and farmers because it produces larger soybean seeds that are richer in protein. Further investigation showed that in the wp mutation, a complicated new DNA insertion into the soybean chromosome triggered flower pigment formation. This complicated DNA rearrangement was catalysed by a natural DNA parasite.

Gracia Zabala and Lila Vodkin

DNA parasites?

[DNA parasites](http://www.nobelprize.org/nobel_prizes/medicine/laureates/1983/mcclintock-lecture.html are foreign DNA. They are triggered into movement to a new chromosome site when plant cells are stressed. This happens when inter-species crop hybrids are formed by cross-pollination (which is often the case in conventional breeding of major food or feed crops such as wheat or Triticale), or by the stresses of cold nights in Sicilian orange groves.

Geneticists have discovered numerous inter-species transfers of genetic parasites, but more to the point, they have discovered examples of movement across species boundaries of other types of genes, such as those involved in important crop physiological activities.

Mark Rain

Just this last February, for instance, scientists from Brown University in the United States showed that genes providing more efficient photosynthesis have moved between distantly related grass species.

All the key features of laboratory genetic manipulation of crops — random DNA insertion in chromosomes, foreign DNA, altered expression of genes, DNA rearrangements — are exhibited by natural genetic mutations that occur in plants.

Our exposure to unexpected genetic events occurring in genetically-engineered food is lower than our exposure to the unintended genetic changes served up by conventional foods we’ve eaten for years. And underpinning this more recent scientific finding is the fact that there’s solid assurance of GM food safety from the intense scientific scrutiny and government oversight that GM food has received at all stages of its development over the last 30 years and more. Food from GM crops is at least as safe as traditional foods.