system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How can scientists be confident that GMOs won't have multigenerational impact?

Pls note, I am not trying to be political/agenda/whatever here. I know there's controversy, I just want to understand the actual science involved.
gpt
Well first of all, because they just change the Genes of the food. All living stuff have different genes, the cow you eat have a different DNA than the banana you eat. So the fact that the genes are changed doesn't change how it interact with you when you eat it. Some of the fear is that suddenly it will affect your body and that you could end up with foreign DNA in your body, but that total nonsense. When you eat anything you end up with foreign DNA in your body, DNA that will be break down as you break down the food for the nutrient and GMO doesn't change that basic fact. They are modified genes, they are not magic.

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Secondly pretty much all our food are already GMO and we were creating them since the first time we started doing agriculture. For thousands of year we were doing breeding and selection of our food to get the best food we could. If you would look at what natural banana or corn look like we wouldn't recognised them . We selected them for thousand of years to what they are today and that modified their genetics.

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So what is the deal with GMO? The only difference is the method with which we do the genetic modification. Instead of breeding and selection that is limited and take several generation of the plant to create significant changes, we can now change the genes directly with our modern tools and methods.

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So ya the vast majority of the fear of GMO is completely nonsense, the fact that we change the genes won't magically change how food work or affect the human body. That said, there is some issues with GMO that can occurs, but those are usually far more subtle than the fear mongering you see on the internet. Some of those problems come from the intellectual properties that are GMO. A company spend a lot of money to develop those GMO and they of course they have a right to get some profit from those products. The problem is that they could decide to change the genes of the seeds to make them infertile to make sure that all of the seeds need to come from them. Another problem is that if one specific GMO is so efficient that it become widespread, and this lack of genetic diversity can be dangerous. In 1950 a disease almost wiped out the main species of Banana that was cultivated, and more genetic diversity can problem our crop from a single disease risking to wipeout a majority of our culture. Another problem is that GMO can be modified to be more resistant to pesticide, which would allow farmer to use more of those. That isn't necessarily a problem, but if they can suddenly put twice more pesticide, maybe a product that was safe wouldn't be anymore until the regulation catch up. 

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Most of those problems can be fixed by proper regulation, but with the speed at which new GMO can be produced, that is harder to do, compare to when we used breeding and selection to create new crops.