A 2011 Cell Research paper from Chen-Yu Zhang at Nanjing University and colleagues reported a fascinating finding: microRNAs from food could be found in the eater's blood. Further, the paper said that those miRNAs could bind to host targets.
That paper, notes Virginia Hughes at Only Human, made a splash, but follow-up studies haven't been able to reproduce the effect with quite the same verve. Many, she says, found the effect to be at much lower levels. (Hughes adds that some of the studies were by Monsanto, which has an interest in saying genetically modified organisms are safe — the Cell Research study was held up as evidence that GMOs could be harmful.)
Two new papers add to this list, prompting Hughes to wonder how researchers decide when to move on from an idea. Ken Witwer from Johns Hopkins, and the first author of a July RNA Biology paper showing little evidence for uptake of dietary miRNAs, says his lab is moving on. "We've convinced ourselves that we're not seeing anything here," he tells Hughes.
By contrast, Pacific Northwest Diabetes Research Institute's David Galas is not — his work, published in PLOS One, has picked up such miRNAs, though at low levels. "The major result is that miRs are difficult to measure accurately," he tells Hughes, adding that the unclear results make following up even more important. "This is an important topic to get pinned down — the potential for new biological phenomena is significant," he says.