|Corn growing in Ohio by Graylight (Flickr) [CC-BY-2.0 (http://creativecommons.org/licenses/by/2.0)]|
via Wikimedia Commons
The results of a unique US agronomic study have been released. Two different commercial maize crops grown in fields with different management histories were tested for composition. One crop was a GM herbicide-tolerant variety in a no-till field treated with glyphosate (Roundup) for the past 10 years. The other was a conventional variety in a field which hadn't been sprayed with Roundup during the previous 5 years. The two fields were separated by a fence. Environmental stresses on the crops were not unusually high that year.
Compositional analysis was by the 'gold standard' technique of chromatographic separation followed by mass spectrometry to identify the components. (Note that such analysis identifies specific substances, not the broad nutrient categories routinely used to assess the animal feeding value of crops.)
As expected, the GM crops had accumulated glyphosate levels equal to the recently set US maximum residue level. Also as expected (because glyphosate is known to bind to certain substances making them unavailable) the GM crop had lower levels of essential mineral nutrients.
Because the two crops were genetically different cultivars, it would be unlikely for their nutrient to be the same. However, the extent of the difference was extreme: with one single exception out of the fourteen minerals measured, the conventional maize had levels six to four-hundred times higher than the GM crop.
Even more unexpected was the discovery of high readings of formaldehyde in the GM maize. None was detected in the conventional one.
Formaldehyde in free chemical form is better known as embalming fluid. It's a mutagen, a suspected carcinogen, a neurotoxin, and it induces changes in proteins similar to the abnormalities found in Alzheimer's disease. Formaldehyde arises as a normal, but closely controlled, biochemical intermediate during plant and animal cell processes, but doesn't exist in the free-state in a healthy organism.
This raises the question of whether some metabolic disturbance of the genetically transformed plants is leading to an imbalance resulting in an unnatural accumulation of formaldehyde.
Another possibility is that, since the zinc level in the GM crop was only 16% of the conventional one and the natural detoxification of formaldehyde involves a zinc-dependent enzyme, the glyphosate-infused GM plants may be failing to remove the toxin as it arises.
Possibly more sinister is that glyphosate itself can be used as a nutrient source by some common soil and plant bacteria, with formaldehyde as a major by-product.
The roots of GM plants are known to exude the glyphosate previously absorbed through the leaves out into the soil. Bacteria subject to long-term, continuous exposure to the herbicide, as in a no-till/glyphosate-tolerant crop system, will be under pressure to evolve metabolic pathways to use glyphosate. And, soil microbes living around the roots can have highly dynamic and adaptive genomes.
Add to this that plant roots tend to attract useful soil bacteria into the area immediately around themselves. GM crops with a high glyphosate content could be actively accumulating bacteria which generate formaldehyde to deal with the excess weed-killer and protect their own health.
What effects could formaldehyde in the diet have?
The Institute of Science in Society notes that:
“Scientific evidence on glyphosate accumulated over three decades documents miscarriages, birth defects, carcinogenesis, endocrine disruption, DNA damage, neurotoxicity, and toxicity to liver and kidney at levels well below recommended agricultural use.”
A US crop nutrition adviser commented that a glyphosate/formaldehyde link could “explain the continuing problems we are witnessing in livestock operations with poor animal health when GM feed stuffs are in the diet”.
It could also explain the Danish pig-farmer whistle-blower's observations 
Seemingly oblivious to this and to the many scientific questions which have surfaced regarding, for example, foetal abnormalities , cancer  digestive system impairment , and chromosome disruption , the US Environmental Protection Agency is considering a substantial increase in the allowed glyphosate residues in food, feed and oils.
WHAT YOU CAN DO
Unless you want to eat livestock embalmed on the hoof or risk being prematurely preserved yourself, it would be a very good idea to demand that the question of formaldehyde accumulation in both herbicide-tolerant crops and crops from continuous no-till systems be fully explored.
 DANISH PIG FARMER WHISTLE-BLOWER - May 2012
 ROUNDUP CAUSES BIRTH-DEFECTS - GMFS Archive, October 2010
 GM MAIZE IS NOT SAFE TO EAT - October 2012
 HOW GM FOODS COULD BE ATTACKING YOU FROM THE INSIDE - January 2013
 ARGENTINEAN DOCTORS REPORT ON PESTICIDE EFFECTS - November 2011
- US EPA hikes glyphosate limits in food and feed - again, GM Watch 3.05.13
- Dr. Mae-Wan Ho, “Stunning” Differences of GM from non-GM Corn, Institute of Science in Society Report, 22.04.13
- Andrew L. Neal et al., April 2012, Benzoxazinoids in Root Exudates of Maize Attract Pseudomonas putida to the Rhizoshpere, PLOS ONE 7(4)
- H. E. O'Brien et al., 2011, Evolution of plant pathogenesis in Pseudomonas syringae: a genomics perspective, Annual Review of Phytopathology
- D. L. Shinabarger and H. D. Braymer, 1986, Glyphosate catabolism by Pseudomonas sp. strain PG2982, Journal of Bacteriology 168(2)