Question: We teach about GM crops now, with a big focus on evaluating the technology and looking at ethics. One of the disadvantages listed is the concern about human consumption and how GM could affect us. We have the enzymes required to digest DNA and DNA is universal, regardless of the order of bases, so I’m wondering how GM foods could actually interact with our bodies differently? Does anyone have any ideas of what could happen in theory?

Nikolai Adamski answered on 7 Jan 2020: last edited 8 Jan 2020 6:33 pm

Dear Katie,

crops grown for human consumption are rightly regulated, although the level of this varies between different technologies. GM crops are under very tight regulations espeically here in Europe. It follows the precautionary principle, which limits (prohibits) the use of new technologies and medicines before sufficient safety tests have been run.
GM crops destined for human consumption follow similar regulations as new drugs, with multiple rounds over a decade or even longer. And since every GM crop is different, each new one has to undergo the same rigourous testing.
These tests look into possible issues with digestion or immune reactions due to the potential creation fo new allergens. A worst case scenario that finds a lot of publicity is the possibility of crops casuing cancer. Cancer medicine has come a long way, but there are many different types of cancer, which are triggered by different stimuli, so this is something that can never truly be fully excluded. But that applies to other technologies as well. I remember when laptop computers were in the press because they might cause testicular cancer; or mobile phones causing ear/brain cancer. What happened with these technologies is that they proved so useful to so many people that these concerns did not find as much traction.
GM crops have not had that moment yet. The first GM crops were modified for herbicide resistance so farmers could kill weeds without killing the valuable crops. These modifications had no discernible use for consumers.
In 1999, a new crop of rice, called the “Golden Rice” was developed. The idea was to enable rice plants to store vitamin A precusors (co-called beta-carotenes) within the rice grain. Vitamin A deficiency is a huge problem in Southeast Asia, leading to blindness in tens of thousands of children each year. Rice is a staple crop in Southeast Asia, so improving its nutrional quality is vital and could improve and even save millions of lives.
Just a few weeks ago (after ~20 years), “Golden Rice” has been approved by the Philippines government after rigourous testing.
https://www.smithsonianmag.com/smart-news/golden-rice-approved-safe-consumption-philippines-180973897/

This is despite massive protests by Anti-GM organisations like Greenpeace, Friends of the Earth etc, who have sabotaged field trials in the Philippines in previous years.
https://www.bbc.co.uk/news/science-environment-23632042

“Golden rice” might be the crop that showcases the possilbe benefits of GM crops not just for farmers, but also consumers and hence might “open the floodgates”. Even then many regulatory hurdles remain like introducing the trait into locally adapted varieties of rice.

The technologies to modify genomes (of plants, animals and bacteria) have moved on in the meantime. Today, a lot of the discussion focuses on genome editing, which the European Court of Justice ruled as a GM technology.
https://www.bbc.co.uk/news/science-environment-44953100

This is despite gene editing not introducing foreign DNA, but merely deleting/modifiying specific DNA nucleotides, which might happen randomly (solar radiation).

I think I digressed a bit. The issue is complex and simple sounbite statements for or against GM technologies cannot address it.

TL;DR
GM foods can possibly create new allergens or cause cancer. So could any other newly released variety of wheat, peas, etc. All new technolgies face these types of backlash. Crops need to be tested to internationally agreed safety standards.