Seth,I think the nutritional quality of GM foods, and how it compares to non GM foods, is something that a lot of people are interested in knowing about and the answer is simple. The conclusion from numerous studies is that crops derived from GMOs, except for those with intentional nutritional changes, are nutritionally equivalent to conventional crops (Lundry et al., 2013; Harrigan et al., 2010).
Your question is about a specific corn study, and with the numbers that you cite, it is natural that people would be alarmed if the findings were accurate. I was able to search for these numbers on the internet, and found the website containing the information that you are referring to. I did note that the website mentions to “keep in mind this is a report, NOT a scientific peer reviewed study and I do not have any other information other than what is in this blog”. If these results were valid, most scientists I know would have rushed to publish this information in a high impact factor, peer-reviewed journal and distribute it broadly so everyone would be aware. The fact that this information has not been published and that there is no other information except what is in the blog does cause one to question the validity of the measurements, methods, and samples. The data have been attributed to De Dell Seeds by way of a company named Profit Pro. Profit Pro will not respond to our inquiry. This is important because I even question whether this information is from measurements of corn, based on some of the variables reported. In addition to the mineral information you mention, the website also reports “cation exchange capacity (CEC)” measurements. CEC measures the maximum quantity of total cations that a soil is capable of holding. CEC is not a measurement that is conducted in corn. Neither is “anaerobic biology”, “aerobic biology”, “chemical content”, or most of the other variables reported. So while I can be certain that the report is reporting data that is NOT from corn, I am not sure if they are reporting soil data or data from another type of sample.
Unfortunately, I was not able to find the original report from which this information was taken or information on the methods by which the data were generated. While I can’t comment directly on the specific information about micronutrient and glyphosate residue levels that you mention, I can tell you what I have observed in my experience as a scientist, and hopefully answer your question in that way. If I understand correctly what you are asking, you are curious to know whether GM crops have similar micronutrient content to non-GM crops, and whether there are residual levels of glyphosate, and if those levels are safe to consume. If after you read this, you feel I misunderstood any part of your question, please let me know and I’ll try to help further.
In answer to the first part of your question, it is important to remember that micronutrient levels in crops vary as a result of many different factors. These factors can include agronomic practices such as fertilization or how closely you plant seeds, the environment, even location within a field. However, genetic modification does not contribute significantly to micronutrient variation. How do we know this? Well, all GM crops undergo rigorous scientific evaluations that contribute to the safety assessment, and in these evaluations a compositional analysis is conducted that measures amounts of key nutrients, and in some cases, amounts of naturally-occurring non-beneficial compounds. The list of compounds that are measured is based on internationally harmonized consensus documents, which are published by the Organization for Economic Cooperation and Development (OECD). You can access these documents here: http://www.oecd.org/science/biotrack/latestdocuments/2/ to get an idea of what is measured, including carbohydrates, fat, and micronutrients. All studies comparing GM crops to their non-GM counterparts to date have shown no biologically-relevant differences in micronutrient levels, and certainly no differences at the magnitudes you posted in your question. One excellent review publication from multiple public-sector scientists can be found here: http://pubs.acs.org/doi/pdf/10.1021/jf302436u where the authors concluded most of the literature available indicates that mineral nutrition in glyphosate-resistant crops is not affected by either the glyphosate resistance trait or by application of glyphosate and that yield data on glyphosate resistant crops do not support the hypotheses that there are substantive mineral nutrition or disease problems that are specific to glyphosate resistant crops. One recent example of composition data can be found in Lundry et al. (2013) http://pubs.acs.org/doi/pdf/10.1021/jf304005n, which shows that amounts of calcium, magnesium, and manganese are equivalent between the GM corn and the conventional comparator.
Micronutrients are essential not only for human and animal health, but they are also very important to the health of the plant itself. For example, if a corn plant really did have 437 times less calcium, basic plant functions such as cell wall growth and normal metabolic processes would be compromised. Thus, the plant would not be able to participate in normal growth and reproductive development. Magnesium and manganese also have important roles in the plant, such as capturing sunlight and converting it to energy for a plant. Thus, a severe deficiency in any one of these nutrients would affect a plant¹s growth and development long before it matured and produced corn grain to be tested, and would be obvious just by looking at a plant. This has not been observed, and farmers certainly would not spend their money to plant GM seeds if the plant did not grow and develop normally. Take a drive into corn growing regions and that normal-looking corn is mostly GM. If this “study” was correct, it wouldn¹t look that way.
To address the second part of your question on glyphosate residue levels on crops that we consume, all uses for any pesticide in crops must be reviewed by the EPA, which then establishes a “tolerance” (the legal limit for a pesticide residues in or on a food) for the crop commodities, only if EPA determines the tolerance is “safe”. There is a clear definition of “safe” in the regulations, which is that there is a reasonable certainty that no harm will result from exposure to the pesticide. EPA starts by reviewing an extensive battery of toxicology tests, and establishes an acceptable dose level for exposure to the pesticide, whether from short-term, acute exposure or long-term, chronic exposure. All uses of the pesticide must be shown to keep the combined exposure within the acceptable level, or the use is not approved. The Maximum Contaminant Level, or MCL, of glyphosate in water was set at 0.7 ppm, or 700 ppb. This is a concentration at which exposure from drinking water will stay below a small fraction of the acceptable dose level for glyphosate. It is not meant to represent actual or expected levels of glyphosate in water. The MCL is also not the appropriate standard for levels of glyphosate in crops. Those are established following a separate process. The tolerance levels for glyphosate in crop commodities are set based on the levels observed in field trials conducted at the maximum proposed use rates at locations throughout the growing regions for the crop. The tolerances for the crop commodities are approved only if the total dietary exposure to the pesticide is within the acceptable dose level. Thus a tolerance level is limited first by the overall total dose that is acceptable (which sets the upper bound), and then is further limited to the amount that could potentially occur when the pesticide is used according to the approved label directions. The most recent EPA dietary exposure assessment of glyphosate was published earlier this year [http://www.gpo.gov/fdsys/pkg/FR-2013-05-01/pdf/2013-10316.pdf]. In conducting the assessment, EPA assumed that all food commodities with tolerances for glyphosate contained residues at the tolerance level, and that 100% of the crop was treated, thus making it a very conservative assessment. The estimated drinking water concentration used in the assessment, based on actual monitoring data as well as modeling data, was 8.11 ppb. The assessment showed that the total exposure from all foods and water was at most only 13% of the acceptable dose level, based on the current approved uses of glyphosate in crops. Additional uses resulting in increased residues and higher tolerances in crop commodities could be approved by EPA in the future, as long as the combined total exposure remained below the acceptable dose level.
You cite a value of 13 ppm glyphosate in seeds. As discussed above, the various analytical results given in the report do not appear to be based on corn. Certainly the glyphosate results do not reflect what we know about residues in corn. EPA has established a tolerance of 5 ppm in corn grain, based on the maximum approved uses of glyphosate in both conventional and GM corn. If a grower applies glyphosate according to the approved uses, the residues should be below the tolerance. Glyphosate residues above the tolerance are an indication that glyphosate was not applied according to the label, and the grain cannot go into the food supply. Note that the glyphosate corn grain tolerance is set well below what would be considered a safety limit, as the total exposure to glyphosate from all crops (including corn) is only 13% of the acceptable dose level.
Please keep in mind that glyphosate has a long history of safe use. Glyphosate does not persist in the environment for an extended period of time. From a toxicological perspective, humans and other mammals don’t even have the metabolic pathway (known as the shikimic acid pathway) that is the target for glyphosate. On one hand, this means that glyphosate cannot interfere with human or animal metabolism through this pathway. On the other hand, this means we need to eat plants, and/or animals that eat plants, in order to get what are termed “essential amino acids”, or the amino acids that are made in the plant, including those made via the shikimic acid pathway, and are essential for us as humans for survival.
There are few foods, if any, that supply the perfect balance of nutrients. This is one of the reasons why variety in our diet is so important and why I try and get my 18-month old daughter to eat more than just noodles. That is still a work in progress, although I have now started experimenting with how many different types of vegetables and meat I can hide in spaghetti sauce.
- Lundry, DR; Burns, JA; Nemeth, MA; and Riordan, SG. 2013. Journal of Agricultural and Food Chemistry 61: 1991-1998. http://pubs.acs.org/doi/pdf/10.1021/jf304005n
- Harrigan et al., 2010: http://www.nature.com/nbt/journal/v28/n5/full/nbt0510-402.html