When I studied biotechnology at university, we discussed genetically modified (GM) products in quite a bit of detail alongside many of the ethical issues associated with these foods. One of our assignments was to write a 3,500 report to discuss the ethics of using gene technology. Initially I was indifferent on the matter, however after studying the subject in so much detail, I formed quite a strong personal opinion.
GM crops have their genetic information altered by changing the sequence contained within the DNA structure. The DNA is essentially the complex code that tells the organism how to function.
Over millions of years, DNA has been altered as a result of natural mutations from evolution. A mutation may occur in some offspring (be it bacteria, plant, animal and so on). If this mutation proves superior to the old genetic code, then the old code will become redundant and eventually the new code will take over.
Consider giraffes as a very basic example. A pack of giraffes with various length necks have survived in a particular location with both tall and short trees - the genetic code for long and short necks are both as effective as each other. Several of them move to a new location where there are only tall trees. The giraffes with short necks die off because they cannot feed themselves. The genetic code for long necks proves superior in this new environment.
Now natural evolution occurs over many, many, many lifetimes - we are talking thousands of years. It is a very slow process. With genetic modification technology, humans are able to implement changes on a large scale within a fraction of a lifetime.
The problem with this is that we cannot predict with 100% certainty the effects of the gene modification. If the DNA of a plant is altered, we do not know the long-term consequences of this on human beings, other animals and the environment. Don't get me wrong - a LOT of research and clinical trials are carried out before releasing genetically modified species into the wild - but how do we know that this will not result in problems 50 years down the track? Could our offspring be adversely affected? Human beings have naturally evolved to consume natural food, not to consume genetically modified food. We really do not know if there will be consequences because this is such a new technology. We also still know very little with regards to genetics.
Ultimately with this gene technology, I do believe that we are playing god. What should be a natural process is now slowly being taken control by human beings. This may or may not have serious consequences down the road.
There are several examples of seemingly good uses (at least in the short-term) of GM crops. For example "golden rice" has been introduced to provide extra nutrients to malnourished people in third world countries. This has resulted in an improvement in their diet, but again the long-term effects are yet to be fully understood.
There is no proof that genetically modified foods do cause cancer or other complications. There is also no proof that genetically modified foods do not cause cancer. There is A LOT of uncertainty on the subject.
So my opinion - avoid GM foods.
With respect to economics, it makes a lot of sense to study genetic engineering. If you can genetically engineer a crop to be resistant to a particular pest, then imagine how many dollars will be saved. Or, if you can GM a crop to grow all year round (rather than just summer), there are very obvious benefits to this too. Even imagine if you could engineer a plant to survive on 50% less water - how much better would Australian farmers cope during a drought?
Plus, with the increasing world population, it also makes sense to look for alternative ways to grow more food. A large portion of the world is starving and genetic modification may be a part of the solution to these problems.
But is it worth it? At our current level of technology, I don't think so. Personally I think that we are far too primitive as a species to even think about artificially altering the natural process of life. But of course, the above arguments also hold some very valid points.