Michael Veiga asked:
I know it's been estimated that the human body re-generates itself almost completely every 7 odd years or so (except, I hear, the brain which remains as it is - I never followed on with Biology).
If the adage that "You are what you eat" applies and if one were to *only* eat genetically modified foods for a period of 7 years, would that person's body be considered to be genetically modified as well by the end of the 7 years and what would the health implications of that be?
Michael Veiga, Johannesburg
Kat:: Now itís time to look at your genetics questions. Listener Michael Veiga says ďI heard that the human body re-generates itself almost completely every 7 years or so. If the adage that "You are what you eat" applies and if one were to only eat genetically modified foods for a period of 7 years, would that person's body be considered to be genetically modified as well by the end of the 7 years and what would the health implications of that be?Ē To answer, hereís Michael Regnier from the Wellcome Trust.
Michael:: I think thatís a great question, itís a question we had recently on the Wellcome Trust blog recently. Most of us have heard the mantra ďyou are what you eatĒ, and itís natural to wonder if the genes that we consume and take into our bodies can interact with our genes, which after all are pretty fundamental to who we are and how we feel. But, of course, we eat genes all the time.
Every cell contains DNA, whether itís in a human being or a cow or a fish or a spud or an ear of wheat. So whatever you eat itís going to have a lot of DNA in it. Of course, we donít then take on the features of cows, fish, potatoes and wheat when we eat them, and thatís because when we digest our food, our bodies break it down into its constituent parts, and we take what we need and we excrete the rest. And the same goes for genes.
Rather than taking in whole genes from our food, the DNA is broken down. Itís like if you take a sentence and cut it up into all the individual letters then you can make new words and new sentences out of those letters, and thatís what we do. We use those letters Ė billions of them Ė to copy the words and sentences of our existing genes whenever we need to make new cells.
On top of that, our cells have special enzymes that check the genes that are being copied in this way. Most errors are spotted and fixed, so even if a string of DNA that makes up a non-human gene got through our stomach and got taken up into our cells, the chances are that it would be found and dealt with by those sorts of mechanisms. So, whether itís a normal gene from a normal cow or normal vegetable, or a modified gene, the chances of it getting through and being taken up in our genome are incredibly small.
Given that human beings have been eating foreign genes since forever, without literally becoming what we ate, Iíd say that proves our bodies are pretty well set up to prevent any kind of crossover, and genetically engineered genes are no different.
Kat:: Thanks to Michael Regnier from the Wellcome Trust for that answer. And if youíve got any questions about genes, DNA and genetics, just email them to me at email@example.com.
Your body breaks down food into small units as part of digestion - individual amino acids, fats and sugars.
We normally eat all sorts of hybrids, from grapefruit to mule meat, yet nobody worries until the hybridisation is carried out purposively. I wonder why? alancalverd, Fri, 12th Jul 2013
The major exception is viruses - eg if you eat some Norovirus, a lot of cells in your gut will turn into Norovirus.