The US government has allowed Monsanto and friends to use the argument of "substantial equivalence" to establish that GM food is safe. Wikipedia outlines a good summary of this approach. According to Wikipedia, proteomics and metabolomics are new methods for proving this similarity of modified food to "conventional" food. This seems suspect, due to the fact that we don't really understand the activity of all the compounds in "conventional" food, far from it -- though according to Wikipedia, the range of variation within GM foods is less than within conventional. This isn't necessarily a good thing as we probably don't understand the function of variation within the same types of food -- in terms of diet, variation is pretty important. But besides this, we don't really understand the details of the activity and function and formation of many proteins and enzymes -- I may be wrong, but it seems to me that the normal, non-virulent form of the protein that causes Mad Cow almost certainly looks the same biochemically as the virulent, Cow-Maddening variety. All that's different is the shape (technically, the folding) of the protein -- Mad Cow is a disease where a normal, naturally-occuring protein is turned into a very, very bad one that is really the same protein, just now with a very, very bad attitude.
ALL THAT BEING SAID, my idea was this: the idea that genetic modification is better or more controlled than natural breeding seems farcical to me, and to illustrate, which of these scenarios seems more rational and safer to you:
1. You want a kid. Say, you or your partner has a fertility problem, or you're a single mom, so you choose artificial insemination. Since you're going this direction anyway, you decide to choose from "fathers"/donors based on their traits (assuming you can trust the Sperm Donor data). You choose as a donor a strong, smart African-American man (just, fer-instance, and ignoring the deterministic bias here).
2. You want a kid. Say, you or your partner has a fertility problem, or you're a single mom, so you choose artificial insemination. Since you're going in this direction anyway, you decide you want certain traits, which a scientist than adds to a human embryo using DNA from bacteria and various animals. You choose the strength of a horse and antibiotic resistance of some bacterial strains (just, fer-instance).
Which seems like a better idea in this case? Does a child produced from #2 seem substantially similar to a child from #1? What if a profile of their proteins shows everything to be pretty similar?
Personally, if forced to choose, I'd go with #1.
This is, of course, an appeal to gut reaction, not necessarily logic, but I think in this case gut reaction is valuable -- we really don't fully understand GM food -- or even the proteins and genetic workings of ourselves -- so why do we think a radically different form of transferring DNA, across not-closely-related organisms, is practically the same as transferring DNA in a method established by natural selection over millions of years across very-closely-related organisms, i.e. the same species? Besides which, about half of the studies of GM foods, before such studies were essentially banned in the US, showed some carcinogenic results. AND, GM food isn't even necessary and is much more resource-intensive than any other "natural" method...
Go ahead and do GM research, but let's not eat it or inseminate ourselves with it just yet, what say?
...Nota bene: This is important (i.e. I'm still raving about it) because most of the corn and soybeans in the US are genetically modified, and labelling has successfully been fought back again and again. It seems no huge outbreak of genetically-modifiedalicious illness has broken out, but then again... how would we know? There's nothing we could use at this point to easily distinguish as consumers what maladies may (or may not) be a result of GM food, long-term tests on humans or animals is effectively not allowed right now, and long-term maladies like cancer or other illnesses may take decades more to manifest.... (Organic food, by the way, is the only food with a relative gauruntee of not containing GM ingredients...)