Science Questions

Does eating GM food make you GM too?

Sat, 14th Dec 2013

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Question

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

 

Answer

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 genetics@thenakedscientists.com.

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Your body breaks down food into small units as part of digestion - individual amino acids, fats and sugars.
Your body then reassembles these small units into proteins, fats and sugars that make part of your body, based on the instructions already existing in your DNA.

So even if the food had been genetically modified to include proteins or sugars from a different species, they are still composed of the same basic units, and your body will still build them up into the same human proteins. So eating this kind of genetically modified food would not turn you into a "genetically modified human".

The major risks with genetically modified plants, animals and foods have to do with:

The environment: Will these genetically modified varieties take over the ecosystem and displace the natural varieties?

New Compounds: Is there a significant amount of a new substance in the plant which is not already "generally recognised as safe"? (eg because people are already eating large amounts of it in a different type of plant)

Poisons: Will the previously-edible food now contain poisons which will kill or injure those eating it? (eg an apple expressing snake venom)

Carcinogens: Some types of poisons can damage your DNA and cause cancer

In a sense, food-delivered carcinogens can modify your genes, in addition to the natural carcinogens such as radiation from rocks, carcinogens in existing foods and housing materials, plus artificial sources like cigarette smoke, X-Rays and chemicals in the environment. But carcinogens usually modify DNA in a way which causes random and destructive changes in random cells - not something that you would say turned you into a genetically modified human.

The challenge of regulating genetic engineering is to carefully evaluate any genuinely new substances, as these may interfere with your digestive system, or may include basic units which are not found in nature, and could potentially be poisons or carcinogens in your body.

Even if there are no genuinely new substances, testing must ensure that the introduced genes do not increase the level of poisons or carcinogens in edible parts of the plant, but only introduce characteristics which are helpful for humans (eg vitamins in golden rice) or good for the plant (eg drought tolerance or disease resistance). evan_au, Fri, 12th Jul 2013

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



Not only that but since everything we eat usually has DNA in it why aren't they also worried they'll turn into whatever animal they are eating, say a cow, or pig, or celery? mechanic, Fri, 26th Jul 2013

The major exception is viruses - eg if you eat some Norovirus, a lot of cells in your gut will turn into Norovirus.
Fortunately, most people can clear this nasty little virus in a few days. evan_au, Fri, 26th Jul 2013

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