Role of diet and gut microbiota
How much of the pesticide glyphosate do we ingest and what role does our diet play? These questions were answered by the Max Rubner-Institut (MRI) in a scientific, recently published study with over 300 male and female volunteers. In conclusion, the MRI scientists were able to show that the glyphosate exposure of the study participants was very low.
Glyphosate is the most widely used crop protection product, with global sales of over 800,000 tons per year. How much glyphosate do we ingest and what role does our diet play? The Max Rubner-Institut (MRI) answered these questions in a scientific, recently published study with over 300 male and female volunteers.
In the study conducted at the MRI in Karlsruhe, glyphosate was determined in the urine samples of a whole day, the so-called 24-hour urine, of 301 voluntary healthy participants. Such “human biomonitoring” is the method of choice to determine glyphosate exposure. Glyphosate detected in urine, must have been previously absorbed by the body. Hence, intake levels can be calculated from the glyphosate concentrations in urine.
The MRI study showed that neither glyphosate nor its degradation product AMPA (aminomethylphosphonic acid) were detectable in the 24-hour urine of two-thirds of the participants tested. In the remaining third, glyphosate was detected in the urine, but only in small amounts. After evaluating the data, the MRI scientists were able to show, that the glyphosate intake, calculated from the urine concentrations, was less than one thousandth of the limits set by the EU, namely the Acceptable Daily Intake (ADI) and the Acute Reference Dose (ARfD). The study participants were asked about their nutritional behavior during the period of the study. This made it possible to calculate whether glyphosate found in urine was associated with the consumption of certain foods. The MRI was able to show that there was an association between increased consumption of legumes and higher levels of glyphosate in urine. Such a correlation was also found between the intake of cultivated mushrooms and urinary excretion of AMPA, the degradation product of glyphosate.
In conclusion, the MRI scientists were able to show that the glyphosate exposure of the study participants was very low. The observed associations with the consumption of certain foods are in agreement with the data from the national reports "Plant protection product residues in food" of the Federal Office of Consumer Protection and Food Safety (BVL).
In a further study, the MRI investigated whether the human gut microbiota is able to metabolize glyphosate to its degradation product AMPA. For this purpose, suspensions of fecal samples from 15 adult participants were spiked with glyphosate. After 48 hours of anaerobic incubation, neither a degradation of glyphosate nor a formation of AMPA was detected. Thus, metabolization of glyphosate by the human gut microbiota does not seem to play a role.
Soukup ST, Merz B, Bub A, Hoffmann I, Watzl B, Steinberg P, Kulling SE (2020) Glyphosate and AMPA levels in human urine samples and their correlation with food consumption: results of the cross-sectional KarMeN study in Germany. Archives of Toxicology, 94, 1575–1584. doi: 10.1007/s00204-020-02704-7.
Huch M, Stoll DA, Kulling SE, Soukup ST (2022) Metabolism of glyphosate by the human fecal microbiota. Toxicology Letters, 358, 1-5. doi: 10.1016/j.toxlet.2021.12.013.