Glyphosate cross-contamination of the food chain

SciScoop’s Food Security blogger Ioannis Zabetakis takes a look at recent controversy surrounding glyphosate (Roundup)

In the 1990s, I was studying and then teaching in the University of Leeds and those years were full of the “mad cow disease” scandal and the (still) ongoing debate on GM foods. Both the scientific community and society at large now know that by pressing the land or the animals to produce more, we are causing many undesired side effects and creating, possibly unnecessary, risks to the food chain.

The 2005 study

The most comprehensive worldwide study to date on the safety of GMOs was completed in UK in 2005 (under the scheme of UK Farm Scale Evaluations). The study of winter oil rapeseed, one of Britain’s biggest crops, concluded that wildlife and the environment would suffer if the GM crop were grown in the UK. In this study, the effects of GM and non-GM crops on bees, butterflies, bugs, weeds and other farmland wildlife in two farming regimes were assessed. Large fields were planted half with GM and half with conventional crops and the results compared.

The main finding was that broad leaf weeds, such as chickweed, on which birds rely heavily for food, were far less numerous in GM fields than conventional fields. Some of the grass weeds were more numerous, although this had less direct benefit for wildlife and affected the quality of the crops. These results made it clear that it is not the GM crops that harm wildlife but the herbicide sprayed on them. Fields containing conventional crops are sprayed with a herbicide which usually kills weeds before the crops emerge but herbicide-tolerant GM crops can be sprayed later. The results from the GM crops were that the weedkiller was so effective that there were one-third fewer seeds for birds to eat at the end of the season than in a conventional crop. Two years later there were still 25 percent fewer seeds, even though the weedkiller had not been applied again. These weeds are effectively the bottom of the food chain, so the seeds are vital for farmland birds, which are already in decline. There were also fewer bees and butterflies in the GM crops. All the evidence suggests that it is the herbicide that makes the difference to wildlife. Since GM crops cause the loss of wildlife, it can be suggested that they are not safe [1].

The 2013 review

A few days ago (18th April) a review article on the effect of glyphosate on human’s biological functions was published where it is suggested that this compound could be linked to a range of health problems and diseases, including Parkinson’s, infertility and cancers[2]. This report provided evidence indicating that residues of glyphosate, the main ingredient in Roundup weed killer, which is sprayed over millions of acres of crops, has been found in food. In detail, “glyphosate’s residues have been found in the main foods of the Western diet, comprised primarily of sugar, corn, soy and wheat”. Also, glyphosate inhibits cytochrome P450 (CYP) enzymes that play crucial roles in biology, one of which is to detoxify xenobiotics. Thus, glyphosate enhances the damaging effects of other food borne chemical residues and environmental toxins.

The authors have presented evidence on how interference with CYP enzymes acts synergistically with disruption of the biosynthesis of aromatic amino acids by gut bacteria, as well as impairment in serum sulfate transport. The consequences of these findings are important: most of the diseases and conditions are associated with a Western diet, which include gastrointestinal disorders, obesity, diabetes, heart disease, depression, autism, infertility, cancer and Alzheimer’s disease. The authors concluded that “glyphosate is the “textbook example” of exogenous semiotic entropy: the disruption of homeostasis by environmental toxins”.

What now?

The implications of the new study are paramount: we need to re-assess urgently the use of glyphosate in agriculture. In many GMO-free countries, glyphosate based weedkillers are in use and this leads to human’s exposure to residues of this compound through cross-contamination of the food chain.

Further reading

Effects on weed and invertebrate abundance and diversity of herbicide management in genetically modified herbicide-tolerant winter-sown oilseed rape

Glyphosate’s Suppression of Cytochrome P450 Enzymes and Amino Acid Biosynthesis by the Gut Microbiome: Pathways to Modern Diseases