Recently I saw a post from business insider of Prof. Neil de Grasse Tyson talking about GMOs. He says:
What most people don't know, but they should, is that practically every food you buy in a store for consumption by humans is genetically modified food.
There are no wild seedless watermelons; there's no wild cows; there's no long-stem roses growing in the wild — although we don't eat roses. You list all the fruit, and all the vegetables, and ask yourself: Is there a wild counterpart to this? If there is, it's not as large, it's not as sweet, it's not as juicy, and it has way more seeds in it.
We have systematically genetically modified all the foods, the vegetables and animals, that we have eaten ever since we cultivated them. It's called "artificial selection." That's how we genetically modify them. So now that we can do it in a lab, all of a sudden you're going to complain?
He is correct that almost all our food has been "genetically-modified" through artificial selection, but this process mimics the natural selection, it's much slower and doesn't introduce genes from other animals. What GMO's are is totally different. They are novel processes that introduce genes not found in the host organism from another. Typically this is done through using a disabled virus as a vector. Very different. And while I am pretty sure most are safe(ish) to eat, that's not what worries me most about franken food. It's their impact on ecology.
Besides we still don't know how nutrition works. I'd be very careful with what I recommend is safe in terms of food. Other lab foods like margarine, sorbitol, olestra, and saccharine (once linked to cancer) have been found to have unanticipated side effects much later on.
I looked up saccharine and it turns out they removed the label that it causes cancer in 2000. That's interesting. Saccharine causes cancer in rodents but not necessarily humans. It only took over 20 years to figure that out. Shows how little we know of how nutrition work.
By the way, margarine originally had lots of trans-fats that could cause heart problems due to cholesterol, sorbitol can cause irritable bowel syndrome and olestra diarrhea. All fun stuff.