The food we consume and the resulting benefits/hazards of specific items have been in the spotlight for quite some time now. Each week there is a new food to eat for superior health, and every other week there is another food villain to avoid. This is not surprising given the level of importance food plays in our daily lives. However, it can often be difficult to discern what claims are rooted in science and what falls into the blatantly untrue category. One such claim in the latter is that genetically modified organisms (GMOs) are hazardous due to their altered DNA sequences. The common concern is that by ingesting something with altered DNA, we could in turn cause changes to our own DNA via gene transfer. Supporters of this theory have linked the rise in GMO production and consumption to the rise in autism, Celiac’s disease, etc.
Fortunately, this is completely untrue. We eat the DNA of other organisms every single day, and it is our body’s natural defense to not directly incorporate foreign DNA into our own. Instead, the ingested DNA is broken back down into its most basic building blocks to be used as needed by our bodies, or is simply excreted. Our DNA repair and production systems are among the most tightly controlled systems in the human body and do not take risks on using foreign DNA. Thus this means that genetically modified salmon is not metabolized any differently than organic salmon.
However, while GMOs cannot change our genome on the basis of being genetically modified, it is important to realize the extent to which our genome has been affected by what we eat (without or without any engineering). During the several thousand years before the advent of genetic engineering, humans underwent genetic changes in response to their food sources to let natural selection run its course.
In an exciting recent study from Harvard, researchers profiled ancient DNA sets to look at changes in genomes over a period of 9,000 years. The results showed that the profiles greatly differed before and after the introduction of agriculture. This unsurprisingly confirmed that the production of lactose digestion gene (LCT) indeed increased with the onset of cattle raising, yet also led to some other very interesting observations.
A gene known to assist in the absorption of a specific amino acid was also found highly selected for. Yet while this gene resulted in higher human nutrient levels and therefore increased farmer survival, a variant of the gene has the potential to increase the risk of gastric diseases such as celiac disease, ulcerative colitis, and irritable bowel disease. This points to a potentially negative consequence of agriculture, and suggests that digestive distress caused by foods may have a longer history than originally expected. And one of the most striking findings are the hypothesized effects of agriculture on European skin color. Our earliest hunter-gatherer ancestors had dark skin. However, genes for lighter skin emerged at some later point. A potential explanation for this phenomenon is that once ancient humans switched from predominantly hunting meat to growing crops, they were no longer able to consume sufficient vitamin D. Without a steady supply of vitamin D coming from their diet, early Europeans may have evolved to have lighter skin colors in order to more efficiently absorb vitamin D from sunlight.
So while fascinating from an evolutionary and historical perspective, these results remind us that we truly are what we eat, albeit not in the way some anti-GMO crusaders might think.