Pesticide exposure testing

Pesticide Exposure Testing: What to Measure When You Cannot

Pesticide exposure testing has no validated endpoint for gut effects, and a spot urine level reports the last meal rather than the decade. Measure the terrain instead: laboratory panels, bioimpedance body composition, indirect calorimetry and sudomotor testing each carry a management decision.

Patients ask for a residue test that does not exist. The mechanism is measured, the human endpoint is not, and the screening opportunity sits in the metabolic and autonomic terrain the patient brought with them.

A patient who has read about herbicide residue arrives asking for pesticide exposure testing, and there is no panel that answers her question. No validated method exists for the endpoint she cares about, the effect of a dietary residue on her gut community, and a spot urine level reports her last meal rather than her decade. The mechanistic case is laid out on video in The Antibiotic on Your Salad, chapter 22 of The Angry Gut (Dr. Gurpreet Singh Padda, MD, MBA, MHP, and Ami Michelle Grimes). What follows is the screening question: what to tell her, whom to test, and which measurements change management.

What the mechanism claim is, and what it is not

Glyphosate inhibits a single enzyme in the shikimate pathway. Human cells lack the pathway entirely, which is the basis of the human safety assessment and is correct as far as it goes. Bacteria do not lack it. A structural classification of the enzyme, run over thousands of organisms, assigned 54% of core gut species to the vulnerable form, a proportion its authors flagged as conservative. The counter-analysis matters equally: an expression-based census of reference genomes covering most assigned microbial abundance in human fecal metagenomes found the pathway largely incomplete and largely silent, with some organisms possibly degrading the compound rather than being inhibited by it.

The animal work is where the argument has teeth. Rats dosed for ninety days at the European acceptable daily intake accumulated shikimic acid and its dehydro form in the cecum, a substrate pile-up behind the target enzyme in a living mammal at a regulated dose, with no reflection of those cecal metabolites in serum. A mouse study at roughly the American intake reported altered microbiota with inflammatory markers. The European peer review addressed the microbiome question directly and concluded that without standardized regulatory guidance or harmonized criteria, no definitive conclusion can be drawn from the available studies. That is the honest state of it: a measured mechanism, an unmeasured endpoint in people.

Why is there no pesticide exposure test to order?

Three reasons worth having at hand in the room. First, no study relates measured exposure to gut community composition in a human being, so a result would have no interpretive frame. Second, urinary levels are dominated by recent intake: levels were significantly lower in people who had fasted more than eight hours, in the same national sample of 2,310 specimens where 81.2% of Americans aged six and older tested positive. Third, exposure is to a formulation rather than the molecule, and commercial formulations were more cytotoxic than their active ingredients against human cells, while co-formulant identity is treated as confidential and is often described incorrectly in published work. A test of the pure compound, even if it existed, would be answering a question the patient is not living in.

Who to test, and on what trigger

The productive move is to stop chasing the exposure and start measuring the terrain the patient actually presents with. Reasonable triggers for cardiometabolic and autonomic measurement in this population:

• Unexplained bowel symptoms lasting months with a normal structural workup, particularly alongside central adiposity, hypertension or a family history of type 2 diabetes.
• A recent rebuilding window: repeated antibiotic courses, abdominal surgery or an inpatient stay in the preceding year.
• Distal sensory symptoms accompanying the bowel complaint, where small-fiber function has never been documented.
• Patients already committed to dietary change, who need a baseline rather than a lecture, as set out in the selection criteria.

The rebuilding window is the part I would defend hardest, and it is a mechanistic argument rather than a trial result. An expression census describes a settled community at steady state. It does not describe recolonization, when a depleted community must synthesize aromatic amino acids instead of scavenging them. Patients arriving in your office after antibiotics or surgery are living in exactly that interval.

What each finding changes

Measura [Cardiometabolic and Autonomic Health Analysis] holds no residue assay, no urine herbicide level and no stool sequencing, and it does not diagnose. What it returns to the ordering clinician is the measurable terrain, and each result carries a decision with it.

• Laboratory panels establish fuel handling, inflammatory and organ status, converting a vague exposure worry into a treatable metabolic problem. Which laboratory runs the blood work is documented separately.
• Bioimpedance body composition identifies low lean mass in normal-BMI patients, which redirects the plan toward protein adequacy and resistance loading rather than restriction.
• Indirect calorimetry replaces a predicted resting expenditure with a measured one, which changes the dietary prescription and the follow-up target.
• Sudomotor testing documents small-fiber sweat-gland function, supporting or excluding a neuropathic contribution before further gastroenterology referral.
• Where balance, gait or memory concerns coexist, pair the panel with cognitive assessment and fall prevention.

Documentation and workflow

An exposure conversation that ends in measurement is easier to run from a protocol than from improvisation. A standing order can attach laboratory, body composition and small-fiber testing to a defined trigger, so the request does not depend on which clinician is in the room. Metabolic and functional findings belong in the annual wellness visit record, where they support the quality measures described under MIPS and quality reporting. Discrete results in the chart, rather than a scanned report, are what make repeat measurement interpretable; see getting results into the record.

How to answer the question in clinic

Say the three things that are true and stop. The compound’s entire mechanism is inhibition of an enzyme her bacteria carry and her cells do not. At an accepted dose that enzyme was measurably blocked in the gut of a mammal, and the fingerprint never reached blood, which is where the toxicology package looked. The human study pairing exposure with gut composition has not been run, and its entry criteria would exclude the patient asking. Then offer what is measurable. Declining to test for something is not the same as declining to investigate, and patients can tell the difference.

The full evidence file with the counter-case stated at full strength sits in the book companion for The Angry Gut. The patient-facing explanation is what can actually be measured in you.

Frequently asked questions

References

• Leino, L., Tall, T., Helander, M., Saloniemi, I., Saikkonen, K., Ruuskanen, S., & Puigbò, P. (2021). Classification of the glyphosate target enzyme (5-enolpyruvylshikimate-3-phosphate synthase) for assessing sensitivity of organisms to the herbicide. Journal of Hazardous Materials, 408, 124556. https://doi.org/10.1016/j.jhazmat.2020.124556
• Mesnage, R., & Antoniou, M. N. (2020). Computational modelling provides insight into the effects of glyphosate on the shikimate pathway in the human gut microbiome. Current Research in Toxicology, 1, 25-33. https://doi.org/10.1016/j.crtox.2020.04.001
• Mesnage, R., Teixeira, M., Mandrioli, D., Falcioni, L., Ducarmon, Q. R., Zwittink, R. D., Mazzacuva, F., Caldwell, A., Halket, J., Amiel, C., Panoff, J.-M., Belpoggi, F., & Antoniou, M. N. (2021). Use of shotgun metagenomics and metabolomics to evaluate the impact of glyphosate or Roundup MON 52276 on the gut microbiota and serum metabolome of Sprague-Dawley rats. Environmental Health Perspectives, 129(1), 17005. https://doi.org/10.1289/EHP6990
• Ospina, M., Schütze, A., Morales-Agudelo, P., Vidal, M., Wong, L.-Y., & Calafat, A. M. (2022). Exposure to glyphosate in the United States: Data from the 2013-2014 National Health and Nutrition Examination Survey. Environment International, 170, 107620. https://doi.org/10.1016/j.envint.2022.107620
• Ferguson, S., Mesnage, R., & Antoniou, M. N. (2022). Cytotoxicity mechanisms of eight major herbicide active ingredients in comparison to their commercial formulations. Toxics, 10(11), 711. https://doi.org/10.3390/toxics10110711
• Mesnage, R., Benbrook, C., & Antoniou, M. N. (2019). Insight into the confusion over surfactant co-formulants in glyphosate-based herbicides. Food and Chemical Toxicology, 128, 137-145. https://doi.org/10.1016/j.fct.2019.03.053
• Lehman, P. C., Cady, N., Ghimire, S., Shahi, S. K., Shrode, R. L., Lehmler, H.-J., & Mangalam, A. K. (2023). Low-dose glyphosate exposure alters gut microbiota composition and modulates gut homeostasis. Environmental Toxicology and Pharmacology, 100, 104149. https://doi.org/10.1016/j.etap.2023.104149

Related reading

• Opioid-Induced Constipation: Screening in Long-Term Therapy
• Cholecystectomy Complications: The Cohort Nobody Re-Screens
• Laboratory Panels

Medically reviewed by Dr. Gurpreet Singh Padda, MD, MBA, MHP, medical director of Measura. Last reviewed September 12, 2026.