Glyphosate's Suppression of Cytochrome P450 Enzymes and Amino Acid Biosynthesis by the Gut Microbiome: Pathways to Modern Diseases
ABSTRACT Glyphosate, the active ingredient in Roundup ® , is the most popular herbicide used worldwide. The industry asserts it is minimally toxic to humans, but here we argue otherwise. Residues are found in the main foods of the Western diet, comprised primarily of sugar, corn, soy and wheat. Glyphosate's inhibition of cytochrome P450 (CYP) enzymes is an overlooked component of its toxicity to mammals. CYP enzymes 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. Negative impact on the body is insidious and manifests slowly over time as inflammation damages cellular systems throughout the body. Here, we show 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. Consequences are most of the diseases and conditions associated with a Western diet, which include gastrointestinal disorders, obesity, diabetes, heart disease, depression, autism, infertility, cancer and Alzheimer's disease. We explain the documented effects of glyphosate and its ability to induce disease, and we show that glyphosate is the "textbook example" of exogenous semiotic entropy: the disruption of homeostasis by environmental toxins.
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ABSTRACT: Glyphosate use in the United States increased from less than 5,000 to more than 80,000 metric tons/yr between 1987 and 2007. Glyphosate is popular due to its ease of use on soybean, cotton, and corn crops that are genetically modified to tolerate it, utility in no-till farming practices, utility in urban areas, and the perception that it has low toxicity and little mobility in the environment. This compilation is the largest and most comprehensive assessment of the environmental occurrence of glyphosate and aminomethylphosphonic acid (AMPA) in the United States conducted to date, summarizing the results of 3,732 water and sediment and 1,018 quality assurance samples collected between 2001 and 2010 from 38 states. Results indicate that glyphosate and AMPA are usually detected together, mobile, and occur widely in the environment. Glyphosate was detected without AMPA in only 2.3% of samples, whereas AMPA was detected without glyphosate in 17.9% of samples. Glyphosate and AMPA were detected frequently in soils and sediment, ditches and drains, precipitation, rivers, and streams; and less frequently in lakes, ponds, and wetlands; soil water; and groundwater. Concentrations of glyphosate were below the levels of concern for humans or wildlife; however, pesticides are often detected in mixtures. Ecosystem effects of chronic low-level exposures to pesticide mixtures are uncertain. The environmental health risk of low-level detections of glyphosate, AMPA, and associated adjuvants and mixtures remain to be determined.JAWRA Journal of the American Water Resources Association 04/2014; 50(2). · 1.96 Impact Factor
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ABSTRACT: Introduction: The occupational toxic risks from agricultural activities in El Salvador affect human and environmental health. The objective of this paper is to describe the management of pesticide by farmers confirmed with a chronic kidney disease of uncertain etiology (CKDu) not associated to diabetes mellitus or hypertension. Methods: The study involved 42 male patients older than 18 years old with confirmed CKDu that have participated in different stages of pesticides manage-ment. This is a cross-sectional study; it was conducted from January to June 2011, in three com-munities of Bajo Lempa region, El Salvador. An interview was especially designed to investigate which pesticides were used and the farmer practices at different stages of pesticide use. Statistical descriptive analysis was carried out for the several studied variables. Results: All interviewed people had a direct relationship with agricultural activities. The majority of patients had poor education, 19% were illiterate and 55% only have primary education. Most farmers with CKDu had been exposed more than 10 years to hazardous pesticides. The most used pesticide was He-donal/2, 4 D (100%). 95% interviewed patients mixed different pesticides and 63% dumped empty pesticide containers in the fields. Interviewees did not use appropriate personal protective equipment (100%). Conclusions: There is high use of hazardous pesticides by patients and some of these are banned and some are legal in El Salvador, but prohibited by other countries. Interviewed CKDu patients had high exposure to toxic pesticides due to the misuse in almost all stages. There is inadequate legislation and a poor law enforcement to prevent the misuse of pesticides in El Sal-vador. R. Mejía et al.Occupational Diseases and Environmental Medicine 08/2014; 2(2):56-70.
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ABSTRACT: Celiac disease, and, more generally, gluten intolerance, is a growing problem worldwide, but especially in North America and Europe, where an estimated 5% of the population now suffers from it. Symptoms include nausea, diarrhea, skin rashes, macrocytic anemia and depression. It is a multifactorial disease associated with numerous nutritional deficiencies as well as reproductive issues and increased risk to thyroid disease, kidney failure and cancer. Here, we propose that glyphosate, the active ingredient in the herbicide, Roundup(®), is the most important causal factor in this epidemic. Fish exposed to glyphosate develop digestive problems that are reminiscent of celiac disease. Celiac disease is associated with imbalances in gut bacteria that can be fully explained by the known effects of glyphosate on gut bacteria. Characteristics of celiac disease point to impairment in many cytochrome P450 enzymes, which are involved with detoxifying environmental toxins, activating vitamin D3, catabolizing vitamin A, and maintaining bile acid production and sulfate supplies to the gut. Glyphosate is known to inhibit cytochrome P450 enzymes. Deficiencies in iron, cobalt, molybdenum, copper and other rare metals associated with celiac disease can be attributed to glyphosate's strong ability to chelate these elements. Deficiencies in tryptophan, tyrosine, methionine and selenomethionine associated with celiac disease match glyphosate's known depletion of these amino acids. Celiac disease patients have an increased risk to non-Hodgkin's lymphoma, which has also been implicated in glyphosate exposure. Reproductive issues associated with celiac disease, such as infertility, miscarriages, and birth defects, can also be explained by glyphosate. Glyphosate residues in wheat and other crops are likely increasing recently due to the growing practice of crop desiccation just prior to the harvest. We argue that the practice of "ripening" sugar cane with glyphosate may explain the recent surge in kidney failure among agricultural workers in Central America. We conclude with a plea to governments to reconsider policies regarding the safety of glyphosate residues in foods.Interdisciplinary toxicology 12/2013; 6(4):159-184.
Entropy 2013, 15, 1416-1463; doi:10.3390/e15041416
Glyphosate’s Suppression of Cytochrome P450 Enzymes and
Amino Acid Biosynthesis by the Gut Microbiome: Pathways to
Anthony Samsel 1 and Stephanie Seneff 2,*
1 Independent Scientist and Consultant, Deerfield, NH 03037, USA;
2 Computer Science and Artificial Intelligence Laboratory, MIT, Cambridge, MA 02139, USA
* Author to whom correspondence should be addressed; E-Mail: Seneff@csail.mit.edu;
Tel.: +1-617-253-0451; Fax: +1-617-258-8642.
Received: 15 January 2013; in revised form: 10 April 2013 / Accepted: 10 April 2013 /
Published: 18 April 2013
Abstract: Glyphosate, the active ingredient in Roundup®, is the most popular herbicide
used worldwide. The industry asserts it is minimally toxic to humans, but here we argue
otherwise. Residues are found in the main foods of the Western diet, comprised primarily
of sugar, corn, soy and wheat. Glyphosate's inhibition of cytochrome P450 (CYP) enzymes
is an overlooked component of its toxicity to mammals. CYP enzymes 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. Negative impact
on the body is insidious and manifests slowly over time as inflammation damages cellular
systems throughout the body. Here, we show 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. Consequences are most of the diseases
and conditions associated with a Western diet, which include gastrointestinal disorders,
obesity, diabetes, heart disease, depression, autism, infertility, cancer and Alzheimer’s
disease. We explain the documented effects of glyphosate and its ability to induce disease,
and we show that glyphosate is the “textbook example” of exogenous semiotic entropy: the
disruption of homeostasis by environmental toxins.
Keywords: glyphosate; cytochrome P450; eNOS; obesity; cardiovascular disease; cancer;
colitis; shikimate pathway; gut microbiome; tryptophan; tyrosine; phenylalanine; methionine;
serotonin; Alzheimer’s disease; Parkinson’s disease; autism; depression
Entropy 2013, 15
PACS Codes: 87.19.xj; 87.19.xr; 87.19.xv; 87.19.xw; 87.19.xb; 87.19.xp
The foodstuffs of the Western diet, primarily grown by industrial agriculture, are increasingly being
produced using a two-part system of engineered plant seeds and toxic chemical application. Novel
bacterial genes are incorporated through genetic engineering, and toxic chemical residues are readily
taken up by the engineered plants. Research indicates that the new bacterial RNA and DNA present in
genetically engineered plants, providing chemical herbicide resistance and other traits, have not yet
fully understood biological effects. This paper however, will only examine the effects of the chemical
glyphosate, the most popular herbicide on the planet.
Glyphosate (N-phosphonomethylglycine), the active ingredient in the herbicide Roundup®, is the
main herbicide in use today in the United States, and increasingly throughout the World, in agriculture
and in lawn maintenance, especially now that the patent has expired. 80% of genetically modified
crops, particularly corn, soy, canola, cotton, sugar beets and most recently alfalfa, are specifically
targeted towards the introduction of genes resistant to glyphosate, the so-called “Roundup Ready®
feature” In humans, only small amounts (~2%) of ingested glyphosate are metabolized to
aminomethylphosphonic acid (AMPA), and the rest enters the blood stream and is eventually
eliminated through the urine . Studies have shown sharp increases in glyphosate contamination in
streams in the Midwestern United States following the mid 1990s, pointing to its increasing role as the
herbicide of choice in agriculture . A now common practice of crop desiccation through herbicide
administration shortly before the harvest assures an increased glyphosate presence in food sources as
well [3–5]. The industry asserts that glyphosate is nearly nontoxic to mammals [6,7], and therefore
it is not a problem if glyphosate is ingested in food sources. Acutely, it is claimed to be less toxic than
aspirin [1,6]. As a consequence, measurement of its presence in food is practically nonexistent. A vocal
minority of experts believes that glyphosate may instead be much more toxic than is claimed, although
the effects are only apparent after a considerable time lapse. Thus, while short-term studies in rodents
have shown no apparent toxicity , studies involving life-long exposure in rodents have demonstrated
liver and kidney dysfunction and a greatly increased risk of cancer, with shortened lifespan .
Glyphosate’s claimed mechanism of action in plants is the disruption of the shikimate pathway,
which is involved with the synthesis of the essential aromatic amino acids, phenylalanine, tyrosine, and
tryptophan . The currently accepted dogma is that glyphosate is not harmful to humans or to any
mammals because the shikimate pathway is absent in all animals. However, this pathway is present in
gut bacteria, which play an important and heretofore largely overlooked role in human physiology [11–14]
through an integrated biosemiotic relationship with the human host. In addition to aiding digestion, the
gut microbiota synthesize vitamins, detoxify xenobiotics, and participitate in immune system
homeostasis and gastrointestinal tract permeability . Furthermore, dietary factors modulate the
microbial composition of the gut . The incidence of inflammatory bowel diseases such as juvenile
onset Crohn’s disease has increased substantially in the last decade in Western Europe  and the
Entropy 2013, 15
United States . It is reasonable to suspect that glyphosate’s impact on gut bacteria may be
contributing to these diseases and conditions.
However, the fact that female rats are highly susceptible to mammary tumors following chronic
exposure to glyphosate  suggests that there may be something else going on. Our systematic search
of the literature has led us to the realization that many of the health problems that appear to be
associated with a Western diet could be explained by biological disruptions that have already been
attributed to glyphosate. These include digestive issues, obesity, autism, Alzheimer’s disease,
depression, Parkinson’s disease, liver diseases, and cancer, among others. While many other
environmental toxins obviously also contribute to these diseases and conditions, we believe that
glyphosate may be the most significant environmental toxin, mainly because it is pervasive and it is
often handled carelessly due to its perceived nontoxicity. In this paper, we will develop the argument
that the recent alarming increase in all of these health issues can be traced back to a combination of gut
dysbiosis, impaired sulfate transport, and suppression of the activity of the various members of the
cytochrome P450 (CYP) family of enzymes. We have found clear evidence that glyphosate disrupts
gut bacteria and suppresses the CYP enzyme class. The connection to sulfate transport is more indirect,
but justifiable from basic principles of biophysics.
In the remainder of this paper, we will first provide evidence from the literature that explains some
of the ways in which glyphosate adversely affects plants, microbes, amphibians and mammals. Section 3
will discuss the role that gut dysbiosis, arguably resulting from glyphosate exposure, plays in
inflammatory bowel disease and its relationship to autism. Section 4 argues that the excess synthesis of
phenolic compounds associated with glyphosate exposure represents a strategy to compensate for
impairments in the transport of free sulfate. Section 5 will provide evidence that glyphosate inhibits
CYP enzymes. Section 6 explains how obesity can arise from depletion of serum tryptophan due to its
sequestering by macrophages responding to inflammation. Section 7 shows how extreme tryptophan
depletion can lead to impaired nutrient absorption and anorexia nervosa. Section 8 provides a brief
review of all the roles played by CYP enzymes in metabolism. Section 9 discusses a likely
consequence to glyphosate’s disruption of the CYP-analog enzyme, endothelial nitric oxide synthase
(eNOS). Section 10 shows how glyphosate’s effects could plausibly lead to brain-related disorders
such as autism, dementia, depression, and Parkinson’s disease. Section 11 mentions several other
health factors that can potentially be linked to glyphosate, including reproductive issues and cancer.
Section 12 discusses the available evidence that glyphosate is contaminating our food supplies,
especially in recent years. Following a discussion section, we sum up our findings with a brief conclusion.
2. Glyphosate’s Pathological Effects: Controlled Studies
It is well established that glyphosate, a member of the general class of organophosphates, inhibits
the enzyme 5-enolpyruvylshikimic acid-3-phosphate synthase (EPSP synthase), the rate-limiting step
in the synthesis of aromatic amino acids in the shikimate pathway in plants . This pathway, while
not present in mammals, is present in algae, Archaea, bacteria, fungi, and prokaryotes, and unicellular
eukaryotic organisms . Indeed, corn and soy crops have both been shown to accumulate excess
shikimate in response to glyphosate exposure . However, a study comparing glyphosate-tolerant
and glyphosate-sensitive carrot cell lines identified several pathologies beyond the inhibition of
Entropy 2013, 15
aromatic amino acids following glyphosate exposure . It was determined that, in addition to
abnormally low levels of tryptophan, phenylalanine and tyrosine, the glyphosate-sensitive cells also
had 50 to 65% reduced levels of serine, glycine and methionine. The reduction in methionine can have
many adverse consequences, as methionine is an essential sulfur-containing amino acid that has to be
supplied from the diet. In addition, there was evidence of excess ammonia in the glyphosate-sensitive
but not the glyphosate-adapted cells. Both cell types readily absorbed glyphosate from the medium,
with a rapid linear uptake observed during the first eight hours following exposure. This demonstrates
that glyphosate would be present in food sources derived from glyphosate-exposed plants.
The excess ammonia observed in glyphosate-treated plants could be due to increased activity of
phenylalanine ammonia lyase (PAL), an enzyme found in plants, animals, and microbes, that catalyzes
the reaction that converts phenylalanine to trans-cinnamate, releasing ammonia . In studies on
transgenic tobacco, it was demonstrated that a decrease in the aromatic amino acid pool sizes (a direct
consequence of glyphosate exposure) results in an enhancement of metabolic flux through the
shikimate pathway, which leads to a rise in PAL activity as well as a doubling of the levels of
chlorogenic acid, a polyphenolic compound related to cinnamate . It has been proposed that
glyphosate achieves part if not all of its growth-retardation effects on plants through induction of PAL
activity . The growth disruption could be due either to toxicity of the derived phenolic compounds 
or to direct toxicity of the ammonia. A study of olive trees showed that there is a direct relationship
between the total phenol concentration and PAL activity, suggesting that PAL is a major producer of
phenolic compounds . Glyphosate has been shown to increase PAL activity in both soybean
seedlings  and in corn .
Under stress-inducing environments, the secondary metabolites derived from certain protein
synthesis pathways become disproportionately important, and enzyme regulation induces dramatic
shifts in the production of the amino acids versus the secondary metabolites. A study comparing
glyphosate exposure with aromatic protein deprivation in plants found several effects in common, but
there was a striking anomaly for glyphosate in that it caused a 20-fold increase in the synthesis of the
rate-limiting enzyme for a pathway leading to flavonoid synthesis, as a side branch of the tryptophan
synthesis pathway . More generally, there is substantial evidence that glyphosate induces the
synthesis of monophenolic compounds as well as the polyphenolic flavonoids, in both plants  and
microbes , with concurrent depletion of aromatic amino acid supplies. When carrots are exposed to
high doses of glyphosate, they produce significant amounts of various phenolic compounds as well as
shikimic acid . The significance of this will become apparent later on in Section 4 on sulfate
transport. Elevated amounts of shikimate-derived benzoic acids such as protocatechuate and gallate are
also found in plants exposed to glyphosate . Strains of nitrogen-fixing bacteria in the soil produce
hydroxybenzoic acids in the presence of glyphosate . This digression towards the competing
pathways to produce phenolic and benzoic acid compounds may well explain the suppression of
aromatic amino acid synthesis by glyphosate.
Even Roundup Ready® crops typically experience slowed growth following glyphosate ap-
plications, and this has been attributed to glyphosate’s role as a chelator of micronutrients. In early
work, glyphosate was shown to interfere with the uptake of the divalent cations, calcium and
magnesium, through soybean roots . Glyphosate severely reduced calcium content in the mitochondria
of both root and leaf cells. Since magnesium was also affected, but potassium was not, the authors
Entropy 2013, 15
suggested that this property might hold for all divalent cations. More recent greenhouse experiments
demonstrated that glyphosate application to the root system decreased the levels of calcium,
magnesium, iron and manganese in the seeds of the plants . It was proposed that glyphosate binds
to and immobilizes all of these divalent micronutrients, impairing their uptake by the plant. These
glyphosate-induced deficiencies would carry over to the food supply, leading to deficiencies in these
nutrients in humans who consume foods derived from glyphosate-exposed crops.
Evidence of disruption of gut bacteria by glyphosate is available for both cattle and poultry. It has
recently been proposed that glyphosate may be a significant factor in the observed increased risk to
Clostridium botulinum infection in cattle in Germany over the past ten to fifteen years .
Glyphosate's demonstrated toxicity to Enterococcus spp. leads to an imbalance in the gut favoring
overgrowth of the toxic Clostridium species. Glyphosate has been shown to have remarkable adverse
effects on the gut biota in poultry , by reducing the number of beneficial bacteria and increasing
the number of pathogenic bacteria in the gut. Highly pathogenic strains of Salmonella and Clostridium
were found to be highly resistant to glyphosate, whereas beneficial bacteria such as Enterococcus,
Bacillus and Lactobacillus were found to be especially susceptible. Due to the antagonistic effect of
the common beneficial bacterium Enterococcus spp. on Clostridia, toxicity of glyphosate to E. spp
could lead to overgrowth of Clostridia and resulting pathologies.
Pseudomonas spp. is an opportunistic pathogen and an antibiotic-resistant Gram-negative bacterium
that has been shown to be able to break down glyphosate to produce usable phosphate and carbon for
amino acid synthesis, but a toxic by-product of the reaction is formaldehyde , which is neurotoxic,
and low levels of formaldehyde can induce amyloid-like misfolding of tau protein in neurons, forming
protein aggregates similar to those observed in association with Alzheimer's disease .
A recent genome-wide study of the effect of glyphosate on E. coli revealed metabolic starvation,
energy drain, and other effects involving genes that are poorly understood , in addition to
suppression of the shikimate pathway. For example, half of the eight genes encoding ATP synthase
were downregulated, suggesting an impairment in mitochondrial ATP synthesis. At the same time,
genes involved in importing sugars were upregulated, which suggests a switch to anaerobic
fermentation, producing pyruvate (a much less efficient solution) rather than oxidizing glucose for full
breakdown to carbon dioxide and water. A switch to anaerobic metabolism is also suggested from a
study showing that, in soil treated with glyphosate, the total count of fungi was significantly increased,
while oxygen consumption was significantly inhibited .
Research conducted by exposing an outdoor aquatic mesocosm (approximating natural conditions)
to two pesticides and two herbicides revealed a unique effect (among the four toxins studied) of the
herbicide, glyphosate, to destroy tadpoles. Following only a two-week exposure period, two species of
tadpoles were completely eliminated and a third one was nearly exterminated, resulting in a 70%
decline in the species richness of tadpoles . Other experiments on bullfrog tadpoles showed that
prior glyphosate exposure reduced the survival rates of tadpoles exposed to the fungal pathogen,
Batrachochytrium dendrobatidis (Bd). . It is thus conceivable that glyphosate may be instrumental
in the worldwide decimation of frogs currently taking place . This also suggests that glyphosate
disrupts embryonic development, a topic to which we will return later.
An insidious issue with glyphosate is that its toxic effects on mammals take considerable time to be
overtly manifested. Studies on Wistar rats exposed to the highest levels of glyphosate allowed in water
Entropy 2013, 15
for human consumption for 30 or 90 days showed enhanced lipid peroxidation and glutathione peroxidase
activity, indicators of oxidative stress . A long-term study conducted on rats showed remarkable
pathologies that became apparent only after the three-month period that is usually allotted for toxicity
trials. In this experiment, rats were monitored over their entire lifespan, while being fed either
genetically modified (GM) or non-GM maize that had been optionally treated with Roundup® . The
rats that were chronically exposed to Roundup® developed several pathologies over the course of their
lifespan, including large mammary tumors in the females and gastrointestinal, liver and kidney
pathologies, especially in the males. The males developed both skin and liver carcinomas. Premature
death in the treated male rats was mostly due to severe hepatorenal insufficiencies. Other researchers
have shown that oral exposure to glyphosate in drinking water can induce DNA damage to mouse cells
drawn from blood and liver .
Researchers have discovered that Roundup® is sometimes much more toxic than glyphosate by
itself, and this discrepancy can be explained by the fact that Roundup® includes a surfactant which
greatly enhances cytotoxic effects of glyphosate . Specifically, the surfactant, TN-20, commonly
found in glyphosate-based herbicides, was studied for its effect on glyphosate toxicity to rat cells in
vitro. The results showed that the combination of the surfactant and glyphosate led to mitochondrial
damage, apoptosis, and necrosis, under conditions where neither substance working alone achieved
this effect. It was proposed that TN-20 disrupts the integrity of the cellular barrier to glyphosate uptake.
A study on three microorganisms commonly used as starters in dairy technologies demonstrated
that Roundup®, but not glyphosate, inhibited microbial growth at lower concentrations than those
recommended in agriculture . This result illustrates an amplified effect of glyphosate's toxicity
through the adjuvants found in Roundup®. The authors also suggested that a recent loss of
microbiodiversity in raw milk may be explained through the same toxic mechanisms.
In humans, a prolonged accidental skin exposure to a glyphosate-surfactant herbicide has been
shown to produce local swelling, bullae, and exuding wounds, followed by osteopenia, neurological
impairment, and reduced nerve conduction . Similarly oral exposure to glyphosate produces
chemical burns and ulceration of the oral cavity .
3. Gut Dysbiosis, Autism and Colitis
It is now well established that autism spectrum disorder (ASD) is associated with dysbiosis in the
gut , and, indeed, this is viewed by many as an important contributor to ASD . An increase in
short chain fatty acids and ammonia in the gut has been found in association with autism [52,53]. Since
these are by-products of anaerobic fermentation, this suggests an overgrowth of anaerobic bacteria
such as Clostridia, Bacteriodetes, and Desulfovibrio. Clostridia have indeed been found in excess in
the feces of autistic children . By-products of fermentation by anaerobes, such as phenols, amines,
ammonia, and hydrogen sulfide, can be toxic to the large bowel [1,8]. A strong link between autism
and hepatic encephalitis has been identified , where the key underlying pathology may be excess
ammonia in the blood stream. Ammonia plays an important role in the etiology of hepatic encephalopathy
associated with both acute and chronic liver dysfunction [56,57]. The source of the ammonia is
believed to be intestinal bacteria, including those in both the small and large intestine . Impaired
liver function prevents detoxification of ammonia via the urea pathway. Thus, the increased activity of
Entropy 2013, 15
PAL induced by glyphosate [27,28] could play a role in creating a hyperammonemic environment in
the gut and initiating subsequent pathology.
Indeed, there is now evidence that gut microbes can produce ammonia from phenylalanine via
PAL . A unique mouse phenotype has recently been identified that is defined by the behavior of its gut
bacteria , and the authors suggest that this phenotype can be explained through increased
metabolism of phenylalanine via the PAL pathway. Furthermore, this unique phenotype is also
associated with excess synthesis of p-cresol, via a pathway involved in tyrosine breakdown. These
authors go on to propose that the known sulfate deficiency associated with autism [61,62] may be
explained by the depletion of sulfate through sulfation of p-cresol produced from tyrosine by
Clostridium difficile in the gut [63,64], in order to detoxify it. As we will explain in the next section,
we believe that, in fact, p-cresol and other phenolic compounds are part of the solution rather than the
cause, with respect to impaired sulfate transport.
C. difficile is a well-established causal factor in colitis . The incidence of C. difficile-associated
disease has increased significantly in North America in recent years, and research into the association
of this increase with inflammatory bowel disease has borne fruit . In an observational study
involving patients in a hospital in Wisconsin between 2000 and 2005, it was shown that C. difficile
infection was almost nonexistent in patients with inflammatory bowel disease prior to 2003, but the
rate grew from 4% to 7% to 16% in 2003, 2004, and 2005. One hypothesis presented was antibiotic
use disrupting the beneficial gut bacteria, but it is conceivable that increased exposure to glyphosate is
contributing to this increase.
A higher level of p-cresol in the urine has been associated with lower residual sulfonation  and with
autism . p-Cresol, formed via anaerobic metabolism of tyrosine by bacteria such as C. difficile , is a
highly toxic carcinogen, which also causes adverse effects on the central nervous system, the
cardiovascular system, lungs, kidney and liver . A recent paper found that formula-fed infants had
an overrepresentation of C. difficile in the gut bacteria . In a case-control study, children with
autism were found to be significantly more likely to have been formula-fed rather than breast-fed .
The study did not distinguish between organic and non-organic formula, but one can surmise that
non-organic soy formula might be contaminated with glyphosate, and this could be a contributing
factor to both the autism and the C. difficile. Urinary bacterial metabolites of phenylalanine, such as
benzoic and phenylacetic acids, and of tyrosine (p-hydroxybenzoic acid and p-hydroxyphenylacetic acid)
have been found to be elevated in association with several different diseases reflecting impaired
intestinal resorption, including coeliac disease, cystic fibrosis, and unclassified diarrhoea . It was
proposed that these metabolites were produced by the gut bacteria. High concentrations of an abnormal
phenylalanine metabolite have been found in the urine of people with autism and schizophrenia, up to
300x normal adult values, which is likely due to multiple species of anaerobic bacteria in the
Clostridium genus . Others have detected abnormally high concentrations of hippurate in the urine
in association with autism . Hippurate is a liver metabolite of benzoic acid . Thus a variety of
different compounds representing a deflection of aromatic amino acid synthesis towards oxidized benzene
derivatives have been found in association with various digestive disorders and neurological disorders.
Studies have convincingly shown an inflammatory mucosal immunopathology in children with
regressive autism characterized by infiltration of intestinal epithelial lymphocytes . The infiltration
of immune system cells like lymyphocytes and eosinophils is a direct response to the impaired barrier
Entropy 2013, 15
function. As will be seen in the next section, we propose that this dysbiosis is caused principally by
impaired sulfate supply to the mucosa, and that the toxic phenolic compounds both assist in correcting
this deficiency and induce inflammatory responses due to their oxidizing effects.
4. Sulfate Transport Impairment and Phenol Synthesis
Autism is a disorder involving impaired social skills and neurodevelopmental delay that has reached
epidemic proportions in recent years, with one in 50 children born in the United States today now
classified on the autism spectrum, according to the U.S. Centers for Disease Control and Prevention.
Impaired sulfur oxidation and low levels of serum sulfate have been established in association with
autism since 1990, as evidenced by the following quote from : “These results indicate that there
may be a fault either in manufacture of sulphate or that sulphate is being used up dramatically on an
unknown toxic substance these children may be producing” (p. 198).
In this section, we develop a novel hypothesis for the effect of glyphosate on aromatic amino acids
in plants and microbes. Our arguments depend upon the observation that glyphosate, a short
carbon-nitrogen chain with a carbonyl group and a phosphate group, is a strong anionic kosmotrope,
since both carbonate and phosphate have this property. Sulfate is also a kosmotrope, whereas nitrate is
a chaotrope. Kosmotropes and chaotropes represent opposite extremes on the Hofmeister series [78,79],
where kosmotropes tend to structure the water surrounding them and to desolubilize proteins, whereas
chaotropes destructure the water and solubilize proteins. Studies on fatalities due to acute over-exposure to
glyphosate reveal hemodynamic disturbances, including intravascular disseminated coagulation (DIC)
and multiple organ failure, associated with high serum concentrations of glyphosate (over 800 mg/L) .
We suspect this has to do with glyphosate's effect as a potent kosmotrope, causing a "salting out" of
blood proteins and resultant coagulation and a “no-flow” situation .
Molecules with a carbon ring and an available attachment site for sulfate (e.g., phenolic
compounds) are attractive for the purpose of transporting sulfate through the bloodstream when the
kosmotropic load is elevated. Phenolic compounds like p-cresol can be readily sulfated in the gut, and
this provides an opportunity to transport sulfate through the hepatic portal vein in the presence of
glyphosate. The ring supports a charge distribution that diffuses the negative charge and suppresses the
water-structuring properties of sulfate, thus preventing the vascular disturbances. A single phenol can
perform this feat multiple times, as the sulfate can be attached to the phenol in the colon via a phenol
sulfotransferase, and the liver utilizes sulfatases and sulfotransferases to transfer the sulfate moiety
from the phenol to an available substrate, typically a xenobiotic or a sterol . Thus, phenols could
be responsible for supplying the sulfate critically needed to detoxify xenobiotics and bile acids and to
produce various sterol sulfates, as well as supplying sulfate to the pancreas to be incorporated into
mucopolysaccharides being released into the gut along with proteases by acinar cells .
In this scenario, the glyphosate itself, due to its kosmotropic properties, is disrupting the transport
of free sulfate, and therefore the aromatic amino acids are oxidized into various phenolic compounds
in order to compensate for this problem. Unfortunately, once they are unsulfated, the phenols become
toxic, as they will react destructively with phospholipids and DNA through one-electron transfer .
Although flavonoids are generally considered to be beneficial to health, the biological mechanisms
behind their benefit are not yet established. In , it is stated that “the potential role of microbial
Entropy 2013, 15
metabolism in the gastrointestinal tract is often overlooked”. These authors propose that monophenolic
derivatives are likely produced through ring fission of flavonoids by the gut microflora in the colon.
Thus, flavonoids can promote sulfate transport to the liver via this process. Furthermore, flavonoids
themselves can be both glucuronylated and sulfated [85,86], especially at the 4'-OH position , so
they could serve directly as sulfate transporters without being broken down. In fact, we hypothesize
that their role in sulfate transport is the reason for their abundant synthesis in plants in the presence of
glyphosate at the expense of tryptophan . Since they are less toxic than monophenols, they become
attractive for sulfate transport in the presence of glyphosate.
Figure 1. Schematic of cyclical process that could be utilized to transport sulfate from the
gut to the liver in the face of glyphosate contamination in the hepatic portal vein. Phenolic
compounds derived from aromatic amino acids would be cycled back and forth between
the gut and the liver, sulfated during transport from the gut to the liver and glucuronylated
during transport back from the liver to the gut. Ultimately, a sulfate reducing bacterium
could metabolize the phenol, consuming sulfate.
The fact that glyphosate suppresses both alkaline and acid phosphatase activity in in vitro assays 
as well as extracellular alkaline phosphatase synthesis in algae  suggests that phosphate faces the
same problem as sulfate in plants, in the presence of glyphosate, and hence enzymatic activity that
produces free phosphate is suppressed. It is interesting to note that autism is associated with elevated
serum levels of pyridoxal phosphate (vitamin B6) even in the absence of supplements . Despite
this, supplemental B6 has been shown to alleviate symptoms of autism [91,92]. We hypothesize that
vitamin B6 is exploited to transport phosphate safely in the presence of glyphosate. The pyridoxal ring
distributes the negative charge on the phosphate anion in the same way that phenols distribute the
charge on sulfate, thus allowing phosphate to be transported in a non-kosmotropic form.
Glyphosate’s kosmotropic effects can be counteracted through buffering of chaotropes in the blood,
and this could be a factor in the increased levels of both ammonia  and various oxides of nitrogen,
including nitric oxide, nitrite, and nitrate [94–96] observed in association with autism.
Hepa c portal vein
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Thus, autism is associated with dysbiosis in the gut [50,51], along with impaired sulfate metabolism and
a significantly reduced level of free sulfate in the blood stream (only one-third of the normal level)
[63,97–101], excess production of nitric oxide [94–96], overgrowth of phenol-producing bacteria like
C. difficile , and increased urinary levels of the toxic phenol, p-cresol . Autism is also
associated with a decreased ability to sulfate and hence detoxify acetaminophen, which aligns with
insufficient sulfate bioavailability. A genetic defect in the phenol sulfotransferase gene is associated
with autism : this enzyme becomes more essential in the context of glyphosate contamination. All
of these observations can potentially be explained by the effects of glyphosate on the gut bacteria and
on the blood stream.
Both colitis and Crohn’s disease are associated with sulfate depletion in the gut , which could
be caused by the impaired sulfate transport problem induced by glyphosate exposure. An overgrowth
of the sulfur-reducing bacterium, Desulfovibrio, has been found in association with autism .
Sulfate-reducing bacteria can utilize aliphatic and aromatic hydrocarbons as electron donors, and
therefore they can play an important role in detoxifying toxic phenolic compounds [104–108]. Thus,
the presence of Desulfovibrio in the gut may serve a dual purpose by metabolizing phenolic compounds
while also disposing of free sulfate, which could be problematic if allowed to enter the blood stream in
the presence of glyphosate. Thus, we hypothesize that, in the context of glyphosate in the vasculature,
aromatic amino acids are diverted into phenolic compounds which can safely transport sulfate from the
gut to the liver. The liver can then transfer the sulfate to another metabolite, such as a steroid, and then
ship the phenol back to the digestive system for another round via the bile acids following
glucuronidation . Possibly after multiple rounds, the phenol is finally metabolized by a sulfate-reducing
bacterium in the colon. This idea is schematized in Figure 1.
5. Evidence that Glyphosate Inhibits CYP Enzymes
The evidence that glyphosate inhibits CYP enzymes comes from several directions. There are
studies showing inhibition of aromatase, a CYP enzyme that converts testosterone to estrogen, and
studies showing enhancement of retinoic acid, which could be achieved by suppressing the CYP
enzyme involved in its catabolism. Finally, there are studies that directly show inhibition of
detoxifying CYP enzymes in both plants and animals.
Two studies point to a disruption of aromatase activity [109,110]. In , as little as 10 ppm. of
glyphosate disrupted aromatase activity in human liver HepG2 cells, a well-established cell line to
study xenobiotic toxicity. In , it was shown that aromatase activity is disrupted in human
placental cells at a concentration 100 times lower than that recommended in agricultural use.
Furthermore, even small amounts of the adjuvants present in Roundup® could substantially enhance
this effect of glyphosate, probably by enhancing the ease with which it gains access to the membrane-bound
protein. In experiments with oyster larvae, Roundup® was found to be toxic at less than 1/20 the
concentration of glyphosate needed to induce toxicity, thus exhibiting the enormous enhancing effect
of Roundup®'s adjuvants .
Retinoic acid plays a key role in embryonic development, where its tightly-regulated concentration
levels impact developmental stages . Due to reports of neural defects and craniofacial
malformations in children born in regions where glyphosate-based herbicides are used, a group of
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researchers investigated the effects of low doses of glyphosate (1/5,000 dilutions of a commercial
glyphosate-based herbicide) in development of African clawed frog embryos and chick embryos .
The treated embryos were highly abnormal: the frog embryos developed into tadpoles with cranial
deformities, and microcephaly was observed in the chick embryos. They traced this effect to an
increase in endogenous retinoic acid (RA) activity, and showed that cotreatment with an RA antagonist
prevented the deformities.
This increase in RA activity can be explained via inhibition of a CYP enzyme. A novel
member of the CYP family has been discovered which is induced by retinoic acid and involved
in its catabolism [114,115]. It is present in mammalian embryos and in the brain. Thus, if this
enzyme is suppressed by glyphosate, it would explain the observed effect that glyphosate enhances
levels of retinoic acid in embryonic development.
A study conducted in 1998 demonstrated that glyphosate inhibits cytochrome P450 enzymes in
plants . CYP71s are a class of CYP enzymes which play a role in detoxification of benzene
compounds. An inhibitory effect on CYP71B1l extracted from the plant, Thlaspi arvensae, was
demonstrated through an experiment involving a reconstituted system containing E. coli bacterial
membranes expressing a fusion protein of CYP71B fused with a cytochrome P450 reductase. The
fusion protein was assayed for activity level in hydrolyzing a benzo(a)pyrene, in the presence of
various concentrations of glyphosate. At 15 microM concentration of glyphosate, enzyme activity was
reduced by a factor of four, and by 35 microM concentration enzyme activity was completely
eliminated. The mechanism of inhibition involved binding of the nitrogen group in glyphosate to the
haem pocket in the enzyme.
A more compelling study demonstrating an effect in mammals as well as in plants involved giving
rats glyphosate intragastrically for two weeks . A decrease in the hepatic level of cytochrome
P450 activity was observed. As we will see later, CYP enzymes play many important roles in the liver.
It is plausible that glyphosate could serve as a source for carcinogenic nitrosamine exposure in
humans, leading to hepatic carcinoma. N-nitrosylation of glyphosate occurs in soils treated with
sodium nitrite , and plant uptake of the nitrosylated product has been demonstrated .
Preneoplastic and neoplastic lesions in the liver of female Wistar rats exposed to carcinogenic
nitrosamines showed reduced levels of several CYP enzymes involved with detoxification of
xenobiotics, including NADPH-cytochrome P450 reductase and various glutathione transferases .
Hence this becomes a plausible mechanism by which glyphosate might reduce the bioavailability of
CYP enzymes in the liver.
Glyphosate is an organophosphate. Inhibition of CYP enzyme activity in human hepatic cells is a
well-established property of organophosphates commonly used as pesticides . In , it was
demonstrated that organophosphates upregulate the nuclear receptor, constitutive androstane receptor
(CAR), a key regulator of CYP activity. This resulted in increased synthesis of CYP2 mRNA, which
they proposed may be a compensation for inhibition of CYP enzyme activity by the toxin. CYP2 plays
an important role in detoxifying xenobiotics .
Beginning in around 2006, an alarming die-off of honeybees became apparent in the United States,
and researchers are still struggling to understand what is causing this die-off . Since the
application of glyphosate also reached record levels that year, and has continued to increase since then,
with no abatement in the bee colony collapse disorder, glyphosate could be playing a role in the bees'
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plight. While correlation does not necessary imply causation, there are strong reasons why glyphosate
might interfere with bees' resistance to other environmental toxins. At first glance, pesticides might be
more highly suspect, since bees are, after all, an insect. However, honeybees have an innate resistance
to most pesticides, which unfortunately depends upon several CYP enzymes. For example, metabolic
detoxification mediated by CYPs contributes significantly to honey bee tolerance of pyrethroid
insecticides . Thus, the fact that glyphosate disrupts CYP enzymes would suggest that exposure
to glyphosate would leave bees especially vulnerable to pesticides in their environment, resulting in a
synergistic effect. A 2005 study in Alberta (Canada) revealed a reduced wild bee abundance and
highly-correlated reduced pollination in GM canola compared with organically grown canola ,
with Roundup-treated non-GM canola coming in at an intermediate level. A study comparing bees
exposed to glyphosate and/or Roundup® against a control population demonstrated a significantly higher
mortality rate in the glyphosate-exposed bees (p < 0.001) . Neonicotinoids such as imidacloprid
and clothianidin can kill bees, and have been implicated in colony collapse disorder . However,
this toxic effect is likely synergistic in combination with glyphosate, as would occur with bees
ingesting herbicide-contaminated pollen. Glyphosate is an organophosphate, and a study of human
self-poisoning has demonstrated that organophosphate ingestion synergistically greatly enhances the
toxicity of ingested neonicotinoids .
6. The Path to Obesity
Having established a plausible mechanism whereby glyphosate’s effects on gut bacteria would lead
to depleted sulfate supplies in the gut with resulting inflammatory bowel disease, we now turn our
attention towards the likely consequences of the resulting “leaky gut syndrome.” It has been proposed
that the exponential increase in the production of synthetic organic and inorganic chemicals may be
causal in the current world-wide obesity epidemic, due to alterations in body chemistry that promote
weight gain . These chemicals are better known for causing weight loss at high exposure levels,
and this apparent paradox can be explained with respect to glyphosate, by invoking its known effect of
depleting tryptophan in plants and microbes. Its effect on CYP enzymes in the liver will compound the
problem, due to the impaired ability to detoxify synthetic chemicals, which are increasingly present in
the environment. In this section we will explain how glyphosate’s depletion of tryptophan bioavailability
can lead to obesity, and in Section 6 we will provide evidence that extreme depletion of tryptophan in
the absence of obesity can cause severe impairment of the intestinal barriers, resulting in weight loss
and anorexia, due to an inability to transport critical micronutrients across the damaged gut barrier.
Tryptophan is an essential amino acid, meaning that mammalian cells cannot synthesize it. Serum
tryptophan depletion leads to serotonin and melatonin depletion in the brain . Since serotonin
(derived from tryptophan) is a potent appetite suppressant , it follows that serotonin deficiency
would lead to overeating and obesity. As we have seen, tryptophan supplies could be depleted both in
plant-based food sources and through impaired tryptophan synthesis by gut bacteria as direct effects of
glyphosate. The observed 20-fold increase in the synthesis of tryptophan-derived polyphenolic flavonoids
in the context of glyphosate provides strong evidence of impaired tryptophan synthesis .
Tryptophan has several important roles in the body. Ordinarily, dietary tryptophan (aside from its
role as an essential amino acid in protein synthesis) is taken up by the liver and either fully
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metabolized to produce ATP or processed through the enzymatic action of tryptophan dioxygenase
(TDO) and indole amine dioxygenase (IDO), via a pathway involving kynurenine and quinolinate as
intermediaries to produce NAD+, an essential cofactor in ATP synthesis and DNA repair  (see
Figure 2). Any tryptophan not taken up by the liver circulates in the blood, and is transported across
the blood brain barrier (BBB). It becomes the (sole) precursor to the synthesis of the neurotransmitter
serotonin and the hormone melatonin . A low ratio of tryptophan to competing proteins in the
blood stream leads to reduced transport of tryptophan across the BBB and subsequent impaired
serotonin and melatonin synthesis in the brain. Thus, low serum tryptophan levels translates into a
tendency towards weight gain due to suppressed serotonin signaling .
Figure 2. Illustration of tryptophan pathways in the body and the adverse effect of
glyphosate on tryptophan bioavailability. IDO: indole amine dioxygenase; TDO:
Tryptophan dioxygenase; G: glyphosate.
However, under inflammatory conditions, and in response to pathogenic stimuli such as the
lipopolysaccharide (LPS) in bacterial cell walls, tryptophan is converted into kynurenine by lymphoid
tissues at the site of inflammation  and stockpiled by in situ macrophages and neutrophils [135–137]
as kynurenine. Therefore, it is expected that inflammation in the gut would lead directly to serum
tryptophan depletion, thus further reducing the bioavailability of tryptophan to the liver. There are
several reasons why macrophages need to sequester kynurenine, the most important of which is likely
to be the assurance of a localized resource to regenerate NAD+ following its depletion through the
synthesis of poly-ADP ribose by poly(ADP-ribose)polymerase (PARP) [138–140]. Poly-ADP ribose
plays an important role in the DNA repair mechanisms that are required following DNA damage,
induced by the reactive oxygen and nitrogen species (ROS and RNS) released by macrophages to fight
infection – superoxide, nitric oxide, and their reaction product, peroxynitrite. Superoxide is induced
from oxygen in the artery wall by transfer of an electron from cytosolic NADPH to oxygen, and its
synthesis is essential for killing invasive pathogens, but collateral exposure also leads to tissue damage.
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Both the inflammatory cytokine interferon-? (IFN-?) and superoxide itself induce IDO synthesis,
and IDO detoxifies superoxide by using it to break the pyrrole ring in tryptophan . The DNA in
the cell nucleus is highly vulnerable to superoxide exposure, which can lead to strand breaks. The
synthesis of kynurenine from tryptophan by IDO results in replenishing the supply of NAD+ and
NADP+, which has been depleted due to the activities of PARP as part of the DNA repair process.
Studies have confirmed that serum tryptophan levels are low in association with obesity [142,143].
In , plasma tryptophan levels were monitored several times over the course of a twenty-four hour
period, and it was confirmed that serum tryptophan levels were chronically depressed, and the levels of
other competing large neutral amino acids were elevated, in obese subjects compared to controls. This
pathology persisted even after weight reduction through intense dieting.
A recent experiment involving transferring a strain of endotoxin-producing bacteria from the gut of
an obese human to the sterile gut of germ-free mice demonstrated the dramatic obesogenic effect that
over-production of endotoxin by gut bacteria can have . These mice became obese over a 16-week
trial period, when concurrently placed on a high-fat diet, and the obesity was associated with a low-grade
chronic inflammatory state. Control germ-free mice on the same diet but without the infective agent
did not become obese. It was hypothesized that chylomicrons produced for fat transport became a
vehicle for endotoxin delivery to blood serum and subsequently to the liver and body fat stores, since
inflammatory cytokines were found predominantly in the liver and epididymal fat pad rather than in
the ilium. Since glyphosate induces a shift in gut bacteria towards endotoxin-producers, this effect can
conceivably explain the association of a high-fat diet with obesity .
The obesity epidemic began in the United States in 1975, simultaneous with the introduction of
glyphosate into the food chain, and it has steadily escalated in step with increased usage of glyphosate
in agriculture (see Figure 1 in ). While it is common knowledge that Americans are continuing to
grow more and more obese with each passing year [147,148], there may be less awareness that obesity
aligns with glyphosate usage elsewhere in the world . For example, South Africa arguably has the
highest obesity rates in all of Africa , and it is also the African country that has most heavily
embraced glyphosate usage since the 1970’s and has freely adopted genetically modified crops with
little regulation [151,152]. According to World Health Organization statistics , only 2.7% of
adults in the United Kingdom were obese in 1972, a number that rose to 25.8% in 1999. Today, two
thirds of U.K. citizens are either overweight or obese.
7. The Path to Inflammatory Bowel Disease and Anorexia Nervosa
We have seen how obesity can develop following the depletion of tryptophan through its diversion
into polyphenolic flavonoids as well as aggressive uptake into macrophages, to provide assurance of
DNA repair mechanisms in the face of excess ROS and RNS. Subsequent impaired serotonin synthesis
stimulates overeating behaviors. Here, we argue that severe tryptophan deficiency without sufficient
fat stores to harbor toxins and supply sterol sulfates can result in an inability to control microbial
invasion as a consequence of impaired release of antimicrobial peptides. This can lead, paradoxically,
to anorexia nervosa, resulting in a highly inflamed digestive system, pathogenic penetration through
leaky intestinal epithelium, uncontrollable diarrhea, and subsequent anorexia.
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Obesity offers protection against gastrointestinal inflammation, in part because the endotoxin can be
stored in adipose tissue, sparing the gut barrier from inflammatory damage. However, a more
important factor may be the ability of adipose tissue to directly supply sulfated steroids. The
sulfotransferase that sulfates serotonin, thus inactivating it, is found in many tissues, including brain,
heart, liver, lung, kidney and spleen . Insufficient sulfate supply would likely compromise this
function, leading to poor serotonin regulation. There is an interesting connection between levels of
serotonin and sterol sulfates in the blood serum. DHEA sulfate is the most prominent sterol sulfate in
the serum besides cholesterol sulfate . Patients with autism have anomalously low DHEA sulfate
levels along with anomalously low serotonin . Serum DHEA sulfate levels are inversely
associated with visceral fat , and DHEA sulfate supplements can induce weight loss in morbidly
obese postmenopausal women . We hypothesize that DHEA sulfate levels are a hormonal signal
of sulfate bioavailability, and low bioavailability leads to low serotonin which induces overeating, in
order to produce visceral fat. Visceral fat is a source of estrone sulfate , which, we hypothesize,
may compensate for some deficiencies in DHEA sulfate and alleviate the burden on the adrenal glands
to produce sterol sulfates. This would also reduce the demand on phenols to transport sulfate and
therefore alleviate the inflammatory gut disorder, restoring homeostasis.
An important study elucidating the processes leading to inflammatory bowel disorder was
conducted on male Ace2 knockout mice (Ace2?/y) . Ace2 induces expression of the tryptophan
transporter in the gut epithelium. Thus, these mice suffered from severe tryptophan deficiency. They
responded to dextran sodium sulfate exposure with a much more severe colitis attack than their control
littermates, leading to enhanced infiltration of inflammatory cells, increased intestinal bleeding, severe
diarrhea, and weight loss. A series of further experiments revealed that a similar response could be
provoked in the control mice by providing them with a diet that was specifically deficient in
tryptophan. It was confirmed that the acute response was associated with impaired synthesis of
antimicrobial peptides by macrophages, mediated by impaired mTOR (mammalian target of rapamycin)
signaling. It is conceivable that the severe deficiency in tryptophan led to restricted protein synthesis in
macrophages, preventing the synthesis of the antimicrobial peptide. Furthermore, the distribution of gut
bacteria was profoundly affected by the Ace2?/y phenotype and by tryptophan deprivation.
Thus, severe tryptophan deficiency, as might be induced by glyphosate’s interference with
tryptophan synthesis in plants and microbes, can lead to an extreme inflammatory bowel disease that
would severely impair the ability to absorb nutrients through the gut, due to inflammation, bleeding
and diarrhea. This could easily explain the alarming increases that have been seen recently in
inflammatory bowel diseases [16,17,160].
8. Cytochrome P450 Enzymes
The cytochrome P450 (CYP) enzymes are a diverse, ancient class of enzymes that date back to
three billion years ago, and play an important role in plant, animal, and microbial biology . These
enzymes participate in oxidation, peroxidation and reduction of compounds ranging from pharmaceutical
drugs to environmental chemicals to endogenous bioactive molecules . There are at least 18
distinct CYP families in humans, which are classified as a series of numerical “CYP” classes. In
humans, CYP1, CYP2, CYP3, and CYP4 P450 enzymes in the liver are essential for detoxification of