From New Scientist editorial The good news about how food tweaks our genes ( via Ed Yong I’ve got your missing links right here (1 October 2011)):
"EVER since we began farming some 10,000 years ago, we have been genetically modifying the plants we eat. Now it seems that plants have been toggling our genetic switches too, by slipping bits of RNA into our intestines and bloodstreams (see "Eating your greens alters your genes" )."
From the article "Eating your greens alters your genes":
"In what is the strongest evidence yet that the genetic material in food survives digestion and circulates through the body, fragments of plant RNA have been found swimming in the bloodstreams of people and cows. What's more the study by Chen-Yu Zhang of Nanjing University in China and his colleagues shows that some of these plant RNAs muffle gene expression and raise cholesterol levels in mice. The discovery opens up a new way to turn food into medicine: we may be able to design plants that change our genes for the better."
It also suggests that further studies are needed for GM foods and the possibility of concocting useful GM foods.