Is it possible that genetic material in the food we eat–broccoli, steak, lettuce, tomatoes, you name it–affects our own body’s gene expression, and accordingly, our biological fate? Consider how you might approach eating if you knew that small bits of genetic material in your food could alter the genetic functioning of your own body.
Well, it’s likely happening.
As we’ve discussed in this post, we are in fact comprised of many species–bacteria, fungi, and “human” cells–a fantastic orchestration of lifeforms creating the bioresilience of self.
Now evidence suggests that our own gene expression may be regulated by our ingestion of foreign plant and animal genetic material. This evidence furthers an emerging biological comprehension of “self” as a diverse, interconnected, amalgamation of life-stuffs. Our organism is not nearly as contained or isolated from our surroundings as previously thought.
Biology 101: Gene Expression
Let’s review the basics of gene expression. Gene expression is the process by which information in our genes is used to synthesize functional molecules, such as proteins. In gene expression, the code of our DNA, our genotype, contributes to the formation of our observable characteristics and traits, or our phenotype.
In protein formation, segments of DNA are “transcribed” into messenger RNA which are then “translated” into a protein. Proteins then contribute to many number of processes in our body, including catalyzing metabolic pathways, replicating DNA, transporting molecules, and responding to stimuli. Needless to say, protein formation through gene expression is critical to our functioning.
In addition to transcribing messenger RNA, our DNA transcribes many types of functional “noncoding” RNA molecules that perform all sorts of different and important regulatory functions in the cell.
One of the most important classes of these noncoding RNAs are “microRNAs” or miRNAs. These are relatively small molecules (e.g., 19-24 nucleotides) that have the important role of regulating gene expression itself.
Through their interaction with messenger RNA, miRNAs support the normal functioning of all of our bodily systems. They help messenger RNA behave as they should during the translation of proteins. Often, they work to silence messenger RNA, stopping protein translation through negative regulation, but they quite possibly activate new translation through positive regulation.
“Bad” miRNAs (e.g., an miRNA in the wrong place) can contribute to many diseases, including cancer, heart disease, and obesity, as messenger RNAs run amok. (These facts are themselves the result of incredible and recent research.)
New Research Demonstrates Biological Activity from Ingested Micro RNA
We like to think of ourselves and other animals as closed systems. Perhaps as a result of this prejudice, it had been thought that miRNA ingested in our food could never function as an miRNA in our bodies. It seemed an unlikely possibility that miRNA in the plants and animals we eat could avoid degradation (especially if cooked), then travel from our gut to the bloodstream, and then to the tissues and organs where it could start messing with our gene expression.
Well, not only is this possible, but it has recently been shown to occur. In the fall of 2011, a group of Chinese researchers showed that “plant miRNAs in food can regulate the expression of target genes in mammals.”
For humans, the study found several plant miRNAs in human blood serum, but it did not go so far as identifying potential effects on gene expression or the resulting physiological consequence. However, for mice, the study observed that one of the plant miRNAs ingested in uncooked rice worked to decrease their levels of low-density liproprotein (i.e., LDL cholesterol, the good stuff we want more of).
To be clear, the mice were fed quite a bit of uncooked rice for this effect to be observed. But this is phenomenal.
It is suspected that biologically active miRNAs are more prevalent in the meats we eat (given our shared genetics with animals). But plant miRNAs, despite their difference from animal miRNAs, need only six perfectly complementary nucleotides in their “seed” region to match up with our animal messenger RNA and potentially affect our gene expression. Out of the hundreds of plant and animal miRNAs that we eat daily, the number of biologically active miRNAs remains unknown.
The Big Picture
We eat plants and animals. Their microRNAs gets into our blood. This likely affects the expression of our genes (not to mention, possibly the gene expression of all of the bacteria species that inhabit our microbiome!). And gene expression effects everything about us. But the physiological effects, if any, are as of yet unknown. What a wonderful mystery!
These studies certainly give new meaning to “we are what we eat.”
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