"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.
The genetic material in question is microRNA - tiny strands of RNA between 19 and 24 "letters" or nucleotides long. It is found in almost all cells with a nucleus and travels from cell to cell in the blood. Zhang and his colleagues wondered whether all the miRNA strands in our blood are made by our cells - or whether some comes from our food instead."
Even if RNA or DNA does not pass unscathed from food to eater, food can change gene expression in other ways. For example, cosmetics researchers recently suggested that a pill containing a mix of food extracts can influence our genes and boost collagen production in the skin, reducing the appearance of wrinkles (New Scientist, 24 September, p 10).
If Zhang's findings are replicated, we may discover that our blood is swimming with RNA from all kinds of plants. To date, all investigation of this possibility has been motivated by concerns that genes from genetically modified crops could harm health (see "Let's talk about GM crops"). But the new study opens the possibility of designing diets and plants with therapeutic effects.
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