Eli5: If every living thing has DNA in its cells, and DNA contains the instructions for functions of life, why do our bodies NOT interact with the DNA that we consume from eating plants and animals?
In: 5
What do you mean by “interact with” and why *would* one assume that our bodies would “interact with” the DNA as we consume it?
There are enzymes in the small intestine that break down DNA and RNA. Even if it doesn’t, there’s still nothing that it can do unless it makes its way into the nucleus of a cell, and there are a lot of barriers to that happening.
Our bodies read and react to DNA within our individual cells. DNA isn’t just freely floating around in the body – it is contained within each cell. It can’t get into the cell.
So if somehow any of it slips pst our digestive system, it would still just be circulating in the blood waiting to be removed by the body.
The various ways that ingested genetic material actually affects us is an area of active study and obviously not a topic for ELI5.
The simple (and mostly correct) explanation is that the proteins and RNA and DNA in food is digested by the acid and enzymes of the stomach into smaller pieces. The leftover slurry doesn’t have full genomes or anything like that.
Your cells also have mechanisms to destroy foreign DNA and RNA, mostly for viral defense.
There’s some interesting relatively recent research on this: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0069805
Your body is *really* good at separating “inside” from “outside”. Weirdly, the interior of your digestive tract (inside the stomach, intestines, and colon) are all “outside” your body. The food in there, like cells with DNA, are broken down *outside your body* before they are taken into the real “inside”. So it is rare for large pieces of intact DNA to make it inside your body.
Second, your immune system does NOT appreciate free floating DNA. It will trigger an immune response resulting in the very quick destruction of the DNA.
Third, DNA is only useful inside the nucleus of your cells, where there are special enzymes that can make use of it. Those enzymes however, are really tuned to human DNA. Most random DNA won’t do anything even if it gets into the nucleus.
Lastly, DNA is *gigantic*. Functional DNA is just way too big to get from outside a cell to inside a cell. Imagine someone told you had to eat a spaghetti noodle in one bite, but that spaghetti noodle was a mile long.
DNA contains the instructions, but *executing* those instructions is a complex process. You can’t just have DNA floating around and have it do anything: the DNA has to be copied into RNA, which has to bond with another form of RNA in a specific place in your cell, which then has to produce proteins, which then have to actually get to wherever they’re going.
Free DNA can’t do any of this, and it can’t easily get into your cells (which put a lot of effort into keeping foreign DNA out for precisely this reason).
It does, but it’s mainly limited to digesting it and repurposing the nucleotides. In general DNA is only read inside the nucleus, so any free-floating scraps of DNA in the gut are extremely unlikely to start running code.
People have mentioned that DNA in what we consume is broken down and that there isn’t a vector to get that into our DNA.
But interestingly we do have DNA from viruses and bacteria. Our cells also absorbed microcoria, which has completely different DNA from our normal DNA.
Latest Answers