A process of genes expression is when information from your genes translates to the proteins which are primary regulatory entities in cells. "Affects your genes" implies that somehow your genes are changed permanently. MicroRNAs affect the process of gene expression not the genes itself. What the authors found is that microRNAs from rice can appear in cells of mammals if they eat a lot of rice. But if they stop eating rice the effect of these microRNAs will be lost.
If a miRNA alters the expression of transcription factors, chromatin remodeling agents, or other epigenome modifiers, the effect could last long after a person stops eating the miRNA-containing food.
