To start with, what is what we call transgenic? But let's explain some terms we need to know to understand this question, and first of all that of the genome of a species. To put it simple,  the genome of a species is formed by the set of DNA (Deoxyribonucleic Acid) it contains. The DNA, in turn, is the molecule that, through combinations of a 4-letter code, encodes all the information to be transmitted from parents to children, that is, it is something like the instruction manual of any species.  Each segment of DNA that has the information key to producing any given characteristic is called a gene.

A transgenic organism is the one produced by transference of one gene of another species through genome modification techniques (which is known of as genetic engineering). When genetic engineering is used to obtain transgenic organisms, the genome of the species is directly manipulated in order to insert a gene that will provide the characteristics we are looking for (such as immunity to viruses, enhanced resistance towards seasonal changes, etc.).

We should not forget that human beings have modified the characteristics of many different species along the history without using genetic engineering, but by employing traditional techniques instead. One of the best known among those is the cross-breeding of species: for example, the mule, which is the result of cross-breeding a mare and a donkey; or the Dobermans, which are the result of cross-breeding of Rottweiler, Beauceron, Weimaraner, Manchester Terrier and Pinscher breeds. Moreover, we have been continuously selecting fresh varieties of plants that have interested us the most, either because they grew faster or because they bore more fruit. Each of these new variants or crosses with new traits are achieved thanks to modifications undergone at a genomic level by the genes that determine them. But these new individuals are not considered to be transgenic, because proper genetic engineering has not been used on them.

Bearing this in mind the scientific community advocates allowing the use of transgenic species because genetic engineering is a more precise method than the traditional ones in improving food in a quick and safe manner (given that only the chosen gene, which produces the desired effect, is modified), as the latter take longer to produce results and, furthermore, make it impossible to filter out unwanted features, since they do not allow feature selection to be controlled.

To answer the question whether eating transgenic foods may be dangerous, thousands of scientific studies carried out over the last 30 years confirm that eating transgenic food has no more risk for the health than eating non-transgenic equivalents. Including those transgenic plants resistant to some pests in which the introduced gene allows them to produce proteins that are toxic to certain insects (i.e. the plant produces its own pesticide). While this may sound worrying and even unintuitive, it should be noted that toxicity varies with the species studied: for example, chocolate can be harmful to dogs but not to humans, and something similar would happen with this these plants, as they are purpose designed to affect certain insects without affecting humans. In any case, each transgenic species undergoes very strict controls and, in the case of the European Union, its use is not approved until it has been verified that it does not pose a health hazard. Therefore, should there be a problem, no transgenic species would be marketed

But if they are safe for health, where is the problem? The problems surrounding transgenics are more closely related to the environment and the economy than to health. Thus, scientists claim, by means of genetic engineering, transgenic plants can be designed to be more resistant to all extreme temperature changes that we are suffering due to climate change, to need less pesticides, or to produce some added vitamins or further nutrients (such as golden rice) and thereby help curbe world hunger, for example. However, some environmental groups, including Greenpeace, see a future loss of biodiversity in transgenics as the existence of more resistant plants may harden competition and end up eliminating non-transgenic species. In addition to that, numerous farmers would want to grow them, which would increase the said loss of biodiversity problem, and would possibly lead to large crop monopoly companies taking over the market, which can never be a good thing. This, however, would need another post to be properly elaborated.

In short, eating transgenic food is not proven to be dangerous for humans, but it can have other effects (both positive and negative) on the economy and the environment that require further study (and another separate blog entry).

Links to a choice of studies:

1. World Health Organization (WHO)

2. Letter from 110 Nobel Laurates Supporting Precision Agriculture (GMOs)

3. Safety Assessment of Genetically Modified Feed: Is There Any Difference From Food?

4. An overview of the last 10 years of genetically engineered crop safety research