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16 years of GMO agriculture – No meaningful health findings in multiple generations of animals

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cornA new study – Prevalence and impacts of genetically engineered feedstuffs on livestock populations – published last week has brought more evidence to the forefront on the safety profile of genetically modified food (aka GMO).
Transgenic GMO agriculture was first authorized for use in the United States in 1996. Genetic modification of food through the use of artificial selection has been part of agriculture since agriculture started centuries ago. However, since 1996 there’s been a consistent allegation that GMO food is unhealthy for a variety of reasons, primarily stemming from concerns regarding pesticide usage. While I won’t discuss it here, it’s important to remember that pesticides were used before GMO and continue to be used in both GMO and organic farming today.
The authors of this study have taken a novel approach to evaluating whether GMO foods have any negative health effects. Whilst referring to the literally hundreds of safety studies that have been done on transgenic GMO crops since their introduction, the authors looked at the health outcomes of animals raised through the meat and dairy industry. Data on livestock health and productivity have been kept by the USDA since at least 1983 and the authors have compared the data relating to the more than 100 billion animals that have been raised in the United States since the introduction of GMO foods (the primary consumers of GMO foods) to the data on animals raised prior to the introduction of GMO to determine whether there’s been any discernible change in the health of the animals. The results are below:

As the authors state: “All animals arriving at USDA-inspected slaughter facilities undergo both antemortem and postmortem inspections to identify abnormalities. Carcasses are condemned postmortem if there are visible lesions or tumors present on organs and carcasses.” In short, the animals are inspected for any sort of concerning health abnormalities before and after slaughter. Yet since the introduction of GMO based feeds, the incidence of condemnation has remained stable. For broilers, the rates of condemnation have gone down despite the introduction of GMO feeds whilst mortality has remained stable.
If GMO based foods (or the pesticides associated with their cultivation) are systematically unhealthy, we should expect to start to see some of those ramifications in the multiple generations of animals that have been fed them since their introduction. While the average lifespan of broilers (45 days) is shorter than the 90 day studies generally required to establish safety of GMO crops in Europe, the average U.S. dairy cow’s life expectancy is 5 years. At this point several generations of animals have been raised solely with the consumption of GMO based feeds and we still don’t see any evidence of worsening health outcomes.
I should be clear, this evidence is not particularly detailed and should not be taken as anything more than the continuation of a pattern of studies that establish indicative evidence that GMO based diets are no less healthy than non-GMO based diets. Observational studies have limited ability to control for confounding factors. For instance, the improvement in condemnation rates of broilers likely has nothing to do with the introduction of GMO foods and is more likely related to introduction of new handling techniques. But that can’t be established through a purely observational data set such as this. However, if GMO foods (or the pesticides associated with them) are highly carcinogenic or significantly unhealthy at the levels of exposure we receive through eating them after cultivation, we should expect that a data set of this size should be able to start identifying at least some differences in health outcomes pre- and post- the introduction of GMO foods. It appears that we cannot find that difference.

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