Glyphosate and Roundup Alter the Microbiome in Prepuberty

by | Oct 24, 2018 | 2018, Environmental Health

Written by Joyce Smith, BS. This study provides initial evidence that exposures to commonly used GBHs, at doses considered safe, are capable of modifying the gut microbiota in early development, particularly before the onset of puberty and warrants future studies on potential health effects of GBHs in early childhood development.

pesticidesSince Monsanto’s introduction of the glyphosate-based herbicide (GBH) Roundup in 1974, over 9.4 million tons of GBH’s have been sprayed on crops annually, an increase of approximately 100 fold 1. The use of desiccation (the spraying of both GMO and non-GMO crops with glyphosate to hasten harvesting) has significantly increased dietary exposure to glyphosate residues and its primary metabolite AMPA (aminomethyl phosphoric acid) 1. Controversy has dominated the glyphosate dialogue since its declaration as a “probable human carcinogen” by the International Agency for Research on Cancer (IARC), a World Health Organization agency, in 2015 2.

Bacteria, fungi, and plants use the shikimate pathway (a 7-step metabolic route, for the biosynthesis of aromatic amino acids). Glyphosate inhibits this key pathway, causing the plants to die. The Shikamate pathway is non-existent in humans 3; however, our microbiome is susceptible to the potentially damaging consequences of this herbicide that was originally patented as a potential antibiotic 4.

A pilot study by Mao et al 5 investigated whether the composition and diversity of gut microbiome in Sprague-Dawley (SD) rats during early developmental stages is adversely affected by exposure to GBHs at glyphosate doses considered to be “safe”. The United States acceptable daily intake of 1. 75 mg/kg bw/day, is defined as the chronic Reference Dose (cRfD) determined by the United States Environmental Protection Agency 1.

Two groups of twelve SD rat dams and their relative pups were treated with either glyphosate or Roundup diluted in drinking water at glyphosate doses of 1.75 mg/kg body weight per day starting from the 6th gestational day (GD) up to end of lactation. A control group received no herbicide. After weaning, offspring received glyphosate through drinking water until they were sacrificed. Animal feces were collected at multiple time points from both FO dams and F1 pups. Using 165 Polymerase Chain Reaction and sequencing, the gut microbiota of 433 fecal samples were profiled at V3-V4 region of t165 ribosomal RNA gene and further taxonomically assigned and assessed for diversity analysis. The effect of exposure on the overall microbiome and on individual taxa was determined using PERMANOVA and LEfSe analysis respectively.

Low dose exposure to both glyphosate and Roundup resulted in significant and distinctive changes in overall bacterial composition in F1 pups. Specifically at 31 days postnatal, which corresponds to pre-pubertal age in humans, relative abundance for Bacteriodetes (Prevotella) was increased while the Firmicutes (Lactobacillus) was reduced in both Roundup and glyphosate exposed F1 pups compared to controls. (However, these microbiota effects were not evident in adult dams.) Furthermore, overall microbiome diversity and composition 01pere significantly different between the Roundup and glyphosate treated pups. Also the synergistic effects of glyphosate based herbicides with their many adjuvants and surfactants might act differently than glyphosate alone and might potentially increase the toxic effect of glyphosate. 6-8

Study limitations include the undetermined exposure of pups to GBHs in milk 9 and no evaluation of maternal microbiota, and the need for more sophisticated meta-genomics. However, this is only a preliminary pilot study; yet, it provides evidence that maternal exposure to commonly used GBHs at doses currently considered safe at human levels, can potentially modify the gut microbiota in rat pups, particularly before they reach puberty. The microbiota of prepubertal age is more sensitive to GBH exposure than adult microbiota, therefore, suggesting a possible “window of opportunity” for glyphosate-based herbicides to alter the gut microbiota of rat pups. Studies of longer duration are warranted to better understand the increased susceptibility of the microbiota with respect to disease prevention during this critical time frame 10,11 and to explore any potential long term health effects of these glyphosate-induced microbial shifts particularly during prepubertal childhood development.

Source: Mao, Qixing, Fabiana Manservisi, Simona Panzacchi, Daniele Mandrioli, Ilaria Menghetti, Andrea Vornoli, Luciano Bua et al. “The Ramazzini Institute 13-week pilot study on glyphosate and Roundup administered at human-equivalent dose to Sprague Dawley rats: effects on the microbiome.” Environmental Health 17, no. 1 (2018): 50.

© The Author(s). 2018 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/) (http://creativecommons.org/publicdomain/zero/1.0/)

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Posted October 24, 2018.

Joyce Smith, BS, is a degreed laboratory technologist. She received her bachelor of arts with a major in Chemistry and a minor in Biology from the University of Saskatchewan and her internship through the University of Saskatchewan College of Medicine and the Royal University Hospital in Saskatoon, Saskatchewan. She currently resides in Bloomingdale, IL.

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