A study from the National Food Institute at the Technical University of Denmark (DTU) found no evidence that genetic material from food is absorbed in the human body, where it would be able to change the body’s ability to regulate the cholesterol metabolism or influence the immune system.
The study has been carried out in cooperation with researchers from Stockholm, Sweden; Barcelona, Spain, and the University of Copenhagen as well as hospitals in the Capital Region of Denmark.
The study attempted to validate the conclusion from several controversial studies that, in recent years, have put forward the hypothesis that genetic material from food can be absorbed in the body of the person who eats the food.
For example, DTU pointed to a recent study that found small regulatory RNAs — called microRNAs — from rice in the blood of humans and subsequently showed that these can affect the body's cholesterol metabolism. Another study found that microRNAs in breast milk can affect newborns’ immune system.
MicroRNA found only in small amounts
The new DTU study and partners consists of two parts. In the first part, the researchers analyzed available microRNA sequencing data from 824 human blood and tissue samples to see if they contained genetic material that could have been derived from food.
The analysis found that microRNAs from organisms other than humans are present in only 17% of the tissue samples and in 69% of the blood samples -- but in negligible amounts (0.001%) compared to the total amount of microRNA present in the samples. Moreover, the overwhelming majority of the identified foreign microRNA comes from organisms that people rarely eat but are often used in laboratory experiments and animal testing, such as rats and insects, DTU said.
In the second part, the researchers studied blood samples from animals that were given certain feed to see whether the samples contain microRNA from that particular feed. The researchers have been unable to find evidence that microRNA from the feed had entered the animals’ bloodstream.
"The study shows that genetic material from our food is not absorbed into our bodies. If it were possible to influence the body’s functions through microRNA from the food we eat, it would potentially make it possible to develop tablet-based RNA-pharmaceuticals that contain microRNA," postdoctoral research Claus Heiner Bang-Berthelsen from the National Food Institute said.
Both the analysis and the results of the animal study indicate that, when foreign microRNA is found in samples that have been isolated from human blood, it is most likely because the tests have been contaminated with animal or plant material that was present in the laboratory.
The material examined in the study has been copied many times to provide enough material for sequencing, which allows the genetic code to be read. The less material available at the outset, the more times the samples must be copied, which increases the risk of contamination; as such, even the slightest contamination will make a big difference.
"The tiniest bit of dirt on a glove has a much greater significance when analyzing a 0.1 microgram sample of RNA than a 1.0 microgram sample,” Bang-Berthelsen explained.
In the analysis, the researchers observed that the presence of foreign microRNA occurred separately in the different studies and not randomly. This further strengthens the case for laboratory contamination, because if the foreign microRNAs had come from food, the findings would be expected to correspond with what people ate, and there would be greater variety in the findings, DTU said.
According to DTU, the conclusion reached by the National Food Institute and partners is backed up by other studies that have not been able to repeat the results from the studies that suggested that microRNAs from food enter the bloodstream.