We don’t have enough testing for the long-term health effects
There is not enough testing on the long-term health effects of GMOs. The research that has been done has not been long enough and there have not been human trials. If GMOs are chronically toxic, then it will take time to see the implications of GMO consumption. GMOs can also have unexpected and unassessed proteins and these new proteins (such as the engineered heme protein) may be allergens; we do not know their effect. Also, genetic engineering has unintentionally introduced additional fragments of genes to a plant’s DNA and gene-editing (altering the organism’s DNA instead of inserting new genetic material) can have “off-target effects” which means that DNA at a different location can be unintentionally edited. The consequences of this can be hard to predict or detect which is why more testing is needed. Additionally, even the accuracy of the testing that has been done is unclear. Analysis of the research has resulted in different conclusions. The FDA certifies the safety of GMOs but relies on the manufacturer to test them and then only sees a summary of the study. This is problematic in multiple ways since it is a conflict of interest for the manufacturer and research can be interpreted in multiple ways. GMOs may be perfectly safe, but we do not have enough testing to make that claim.
Long term human trials do not make sense to study GMOs. GMOs are designed to be equivalent (in their impact on human health) to non-GMO foods. This means that it would be difficult to design a study that is looking for health effects (unlike with medication where there is an intended change to the human body, and they are looking for side effects). There would also be way too many variables to measure (genetic variability, kind of GMO, amount of consumption, geographic location of crop, etc…). However, there has been extensive testing. GMOs have been tested more than any other food. The safety of GMOs is widely agreed upon by the scientific community, with more than 275 global science organizations coming to the same conclusion that GMOs are as safe as non-GMOs. Additionally, the public has been consuming GMOs since the 1990s which provides a far long enough time period to observe any health problems. These problems have not been seen.
[P1] The research for GMOs hasn't been long or thorough enough. [P2] There haven't been human trials for GMOs. [P3] All new proteins in GMOs have not been assessed. [P4] Accuracy of current testing is unclear. [P5] We have not had enough testing to make an informed decision about whether GMOs are good or bad for our health.
Rejecting the premises
[Rejecting P1] The public has been consuming GMOs since the 1990s and we haven't seen health problems. [Rejecting P2] Designing a long-term human trial to study GMOs would be too difficult. [Rejecting P4] The safety of GMOs is widely agreed upon by independent global scientific organizations. [Rejecting P5] GMOs have been tested more than any other food.