“You are what you eat” says an old proverb. Yet, what if it were literally true? What if material from our food actually made its way into the control centres of our cells, taking charge of fundamental gene expression? That is in fact what happens, according to a recent study in China of plant-animal microRNA transfer. MicroRNAs are short sequences of nucleotides – the building blocks of genetic material. For the study, blood samples from 21 volunteers were tested for the presence of microRNAs from crop plants, such as rice, wheat, potatoes and cabbage. The results of the study revealed that the subjects’ bloodstream contained 30 different microRNAs from commonly eaten plants, and it appears that they alter cell function. For example, a specific rice microRNA was shown to inhibit the genetic receptor that controls the removal of cholesterol from the bloodstream. The suggestion that plant microRNAs play a role in controlling human physiology highlights the fact that our bodies are highly integrated ecosystems. These findings may also illuminate our understanding of co-evolution, a process in which genetic changes in one species trigger changes in another. For example, our ability to digest the lactose in milk arose after we domesticated cattle. Could the plants we cultivated have altered us as well?