My GP and I saw results on my first two weeks of organic food because I had BG tests scheduled already. The huge improvement in my retinopathy, eradication of gum disease and minor anaemia also show me that being additive free helps my body.
Sure, food is comprised of chemicals and we are ourselves. But the human body did not need to handle genetically modified food prior to 1994, for example.
In the U.S. GMOs don't need to be labelled so unless you're eating organic you're eating them.
In New Zealand, GM is far more controlled and lamb isn't allowed to be called New Zealand lamb if fed on GM.(Beef for export can be). This is why Waitrose uses NZ lamb for its ready meals.
In the UK Waitrose is committed to non GM and this includes not feeding it to livestock wherever possible and actively looking for alternatives. Waitrose admits that some non-organic pork is fed GM soya.
Morrisons and ASDA were the first to allow GM feed to be fed to non-organic animals destined either to be eaten themselves or produce products to be eaten (e.g. eggs, milk, butter, cheese, cream, yogurt) in 2012. Tesco, Sainsbury's, Co-op and Marks and Spencer followed. None of these products have to be labelled as coming from GM fed animals.
The majority of mainland European consumers don't want GM and the majority of UK consumers too. But because this stuff doesn't have to be labelled, not many people are aware of it. I read The Grocer, the trade mag for supermarket retailing and this has followed the GM issue.
According to the Food Standards Agency there are no standard tests yet to determine whether GM material does routinely transfer to humans.
The University of Newcastle has proved that it can survive digestion and mutate gut flora, however.
You can also Google and find Danish studies that show that pig health can suffer on GM. If you want to get really scared, go look at YouTube vids made by farmers, detailing what happened to their animals when fed on GM feed.
Personally, I'm not eating GM. I'm not a knockout mouse and refuse to be part of an experiment. In the past people thought that lead, arsenic, mercury and asbestos were safe.