How Glyphosate Disrupts Gut Production of Serotonin, Dopamine, and Melatonin

Your gut isn’t just digesting food—it’s a neurotransmitter factory. Nearly 90% of serotonin is made in the gut, along with dopamine, melatonin, and signaling molecules that regulate mood, sleep, and metabolism.

But here’s the catch: the building blocks for these molecules—phenylalanine, tyrosine, and tryptophan—come from plants and microbes via the shikimate pathway. And that’s exactly where glyphosate, the most widely used herbicide, does its damage.

How Glyphosate Works

Glyphosate blocks an enzyme called EPSPS (5-enolpyruvylshikimate-3-phosphate synthase) in the shikimate pathway. This pathway is how plants and many microbes make three essential amino acids: phenylalanine, tyrosine, and tryptophan.

Humans don’t have this pathway, but we depend on it in two ways:

• Plants in our diet → if crops can’t make these amino acids, their nutrient profile changes.

• Gut microbes → many bacteria in the gut use the shikimate pathway to produce these amino acids, which feed into serotonin, dopamine, melatonin, and thyroid hormone production.

Animal and lab studies show this clearly: glyphosate exposure leads to shikimate build-up in the gut (a biomarker of pathway blockage) and changes in microbiome composition, often with reductions in beneficial species like Lactobacillus and Bifidobacterium  .

In short: glyphosate cuts the neurotransmitter supply chain at its source—by blocking the microbial and plant machinery that makes their amino acid precursors.

Impact on Neurotransmitter Precursors

• Phenylalanine → Tyrosine → Dopamine, Norepinephrine, Epinephrine, Thyroid hormones, Melanin

• Tryptophan → Serotonin, Melatonin, NAD⁺, Immune-modulating indoles

When glyphosate reduces these amino acids, the downstream production of neurotransmitters and hormones can be disrupted.

The Gut–Brain Consequences

• Mood: Lower serotonin & dopamine linked with depression, anxiety, and reduced resilience to stress.

• Sleep & circadian rhythm: Less serotonin → less melatonin → poor sleep and disrupted biological rhythms.

• Energy & metabolism: Reduced tyrosine can impair thyroid hormones, slowing metabolism and energy.

• Immune & gut health: Lower microbial indoles weaken gut barrier and immune tolerance.

Why It Matters Now

Studies show glyphosate exposure alters the gut microbiome, shifts amino acid metabolism, and causes shikimate build-up (a marker of pathway disruption). With glyphosate residues in our water and food, daily exposure is widespread.

How to Reduce Exposure

• Choose organic or glyphosate-free certified products.

• Use a high quality water filter that removes glyphosate (not all filters do!).

• Prioritize a diverse, whole-food diet with protein to ensure amino acid availability.

• Support your gut microbiome with prebiotics, polyphenols, and fermented foods.

• Align eating and light exposure with circadian rhythm to optimize serotonin–melatonin balance.

Unfortunately, most people have accumulated glyphosate over the years and I often see high levels when testing for toxins in the body - even those who have been eating organic and drinking filtered water! The good news is there are ways to support detoxification. If you're interested in testing and/or learning about how to detox glyphosate you can schedule a consultation here.

References:

1. Mesnage R, et al. Toxicology Reports. 2021 – Gut microbiome and metabolome alterations linked to glyphosate and Roundup exposure.

2. Zampieri M, et al. Nature Microbiology. 2020 – Glyphosate-induced accumulation of shikimate as a marker of EPSPS inhibition in microbial communities.