After posting our five-part video series on genetically-modified (GM) foods, we've gotten a lot of feedback and even more questions surrounding the safety of GM foods and crops. We're addressing those questions here since YouTube limits the number of characters for comments and we want to be sure the experts have the ability to respond fully.
In response to the GM 101 video:
Comment from YouTube User "GCN3030": "GM crops do not increase yield. In fact it may be they may even cause crop yield to DECLINE. A US Department of Agriculture report confirmed the poor yield performance of GM crops, saying, 'GE [genetically engineered] crops available for commercial use do not increase the yield potential of a variety. In fact, yield may even decrease...'"
Response from Dr. Sally Mackenzie: It is important to remember that GM is not a catch-all term, and all GM crops are not the same. When we talk about documented increases in yield, these data are applied to Roundup® technologies and BT technologies. In the case of Roundup Ready (herbicide tolerance), the observed yield increases come by virtue of the fact that growers can control weeds more economically and effectively. Without the competition of weeds for nutrients, water and sunlight, the crop grows more healthy, and production has been shown to be higher. This is quite logical, and not unlike what you would see in your own home garden if you are diligent in keeping the weeds in check. These data are supported by what growers in the Midwest see every year, which is why these agricultural systems are so popular with farmers.
With BT (insect tolerance) technology, two benefits come in the form of enhanced yield.
- The first is that insect damage to the plant is reduced, which means a greater yield of higher quality (ie. undamaged) product.
- But, in addition, it turns out that the enhanced resistance to insect pests has the added benefit of reducing the pathogenic fungi that often accompany those insects.
Therefore, post-harvest grain coming from BT engineering has higher storage life with less decay. This also bolsters final yield as an unexpected bonus. Again, this is quite logical. If you prevent insect damage to your crop, more of the crop is harvested, and it comes with less damage, allowing for enhanced post-harvest quality. If these gains were not authentic, farmers would not be such strong proponents of the technology.
Comment from YouTube User "GCN3030": "Roundup Ready brand GM crops are designed so that you can INCREASE the use of herbicides. They have not reduced herbicide use at all. As far as glyphosate being "relatively" benign, that is deliberately misleading. That stuff is EXTREMELY toxic. As little as 10 parts per million can kill fish."
Response from Dr. Sally Mackenzie: Roundup Ready technology is designed to lower farmer inputs ($) in crop production. Herbicides cost the grower money to apply, so Roundup Ready is designed so that the grower can reduce the number of applications, and can apply post-emergence of his crop without damage to the crop. This means fewer applications and less labor in physical weeding of the field. The biodegradable nature of glyphosate, and its very specific targeting of an enzyme involved in amino acid biosynthesis, makes it a much less dangerous herbicide than some of the others used in past agricultural practices. But don't take my word for it; the structure and target of glyphosate are very well-documented and can be found with a simply Google/Wikipedia search. GM technology has nothing to do with verifying the safety or toxicity levels of glyphosate. It goes without saying that all herbicides likely have some level of toxicity to organisms other than plants and we would all be better off if growers were given the opportunity to produce more product with fewer applications of ANY herbicide. GM technologies have been developed to allow the grower to use herbicides other than glyphosate as well, like Dicamba. The message of the videos is not to proclaim the inherent safety of herbicides, but the inherent safety of the GM technologies in crops.
Comment from YouTube User "GCN3030": "How would one go about documenting a health issue caused by GM crops? If I get a health problem like say a tumor that is similar to those experienced by the GM fed animals in the studies that have been done, how will I know whether GM crops that I unknowingly consumed a decade ago caused my problem? Sub-acute long term problems would be very difficult to document particularly when so many people do not even realize that there are many animal studies that have indicated negative effects."
Response from Dr. Sally Mackenzie: This question is relevant to all of the foods we eat. How do we know milk is good for us? Or the meat we eat? Should we be adding fructose corn syrup to our foods? What about eating wheat products? To some sector of the human population, any one of these foods can be damaging to health. And so we rely on regulatory bodies to establish certain testing procedures to ensure what our society considers an appropriate level of safety. With GM crops, the bar is held considerably higher than for any of the foods I mention above. Animal feed testing, DNA sequencing, antigenicity testing are all essential in the testing of a GM product, but these tests are not required for approval of our other foods. As a consequence, we have had significantly greater problems with other parts of our food production systems, including organic production, and no documented problems with GM foods. Presumably, this high level of testing has been effective. Nothing can be guaranteed 100% safe, but I marvel at the high level of concern shown to GM crops, with their rigorous testing, by consumers who recognize and accept that every other part of their food production system has inherent risks.
Comments from YouTube Users:
"GCN3030": "Why don't you address people's real concerns based on the thousands of internal corporate animal studies that were only released after a lawsuit in 1999 because that showed all sorts of different negative effects? Why is there no discussion of the fact that the FDA's own scientists voiced their concern over the results they saw in these studies? Why no mention of the recent results of the French study which used a larger sample size and studied the rats for their entire life? Very one sided."
"Octavio Ayala": "Séralini et al 2012. "...Roundup-tolerant genetically modified maize from 11% in the diet cultivated with or without roundup and roundup alone (from 0.1 ppb in the water) were studied 2 years in rats. In females, all treated groups died 2-3 times more than controls, and more rapidly. this difference was visible in 3 male groups fed GMOs."
Response from Dr. Sally Mackenzie: Scientists are not equipped to deal with anecdotal stories; scientists deal with data generated from well-designed and controlled studies. The study you cite by the French investigator, Gilles-Eric Seralini, that was published in September of this year has a number of problems that make interpretation of his findings very difficult. For example, he uses a specific strain of rats, the albino Sprague-Dawley rat, that has been specifically bred to produce mammary tumors, especially if their diet is not carefully controlled. The investigators never tell you that they saw the same sorts of tumors on their control rats, and they report that they saw more tumors on the diet with less GM grain and lower tumor production on the rats fed higher GM grain. Does this mean that GM grain in higher doses reduces tumor formation? These rats were not bred to be used in longer-term studies, so it is difficult to know how long they should live, and the very small size of the control group (only 20 rats) makes it very difficult to determine whether the rats fed GM were any better or worse off than the control sample. Also, it is worth noting that Seralini cites only studies from his own lab; there appears to be no supporting literature outside of his lab to substantiate these claims. All of these factors leave the scientific community quite dubious about his claims.
These types of experiments are often designed to be misleading. Notice that the hundreds of thousands of studies by recognized scientific experts (many National Academy of Science members) demonstrating the safety of GM products receive absolutely no air time compared to the huge amount of press garnered by Seralini's one, questionable study using a highly mutagenic rat strain.
Comment from YouTube User "1dnc4mun": "Yes, there is strong evidence showing that what they say is true. What they DON'T tell us is MUCH MUCH WORSE. Epigenetic research is showing that human/ bacterial DNA can absorb the genetically altered information and thus produce pesticides. Also, CROSS POLLINATION. When GMO cross pollinates to naturally grown crops, the NGC's produce a mutation with the GMO genetic information. This destroys the natural crops and will eventually force all farmers to grow GMO crops- thus Monsanto will rule."
Response from Dr. Cecilia Chi-Ham: "Horizontal Gene Transfer, the movement of genetic information across unrelated species is known to occur- albeit at a very low frequency. However, there is no scientific evidence to support the expression of a transgene from a GM crop in humans. The BT protein has been shown to be safe to humans and thus used in all farming- organic, conventional and GM.
"With regards to cross-pollination, GM and conventional crops behave the same. What's important to note is that DNA from a GM crop is not any more dangerous than from a conventionallly-bred crop. Moreover, a number of conventionally-bred crops are produced by randomly mutating its DNA. In contrast, GM crops use precise breeding to introduce a new trait."
Still have questions? Ask an expert here.