Glyphosate - Drying Agent and Herbicide for Soy and Wheat and its Potential Health Impacts
Does research show health risks related to glyphosate such as increased cancer and gluten allergy incidence?
This is a blog where I go in-depth into questions and topics, I am personally interested in related to contamination and toxicity. The goal is to break down and interpret the actual data behind many of these compounds in the news for a non-chemist like me. Each blog is based on secondary research, primarily from published articles found through Google Scholar and known academic journals, and experience formed during my work with chemical analysis.
TLDR
Glyphosate and its metabolic derivative AMPA has recently been associated with endocrine disruption and increased cancer risk.
The relationship between concentration and risk is not established or I could not find the information.
Soy protein consumption has the highest correlation with increased concentration of AMPA in urine.
There is circumstantial evidence between glyphosate disrupting gut health and reduced gluten digestion ability.
For this article I picked glyphosate. Something which is quite hard to screen for at trace amounts in foods and I was not entirely sure what to make of its potential toxicity.
What is Glyphosate?
Glyphosate is a weed killer and also a drying agent which is used for crop care and also during early stages of crop processing.
Apparently it became popular when new crops were introduced which were resistant to it, creating a perfect setup for crop care and effective weed elimination (Wiki).
It has quickly grown in popularity and is widely used in the US, mainly for soy and corn:
How good a weed killer is it though? What are the alternatives?
The big benefit of glyphosate is that it moves down to the roots of weeds making it highly effective. The alternatives largely appear to only affect the sprayed areas rather than the whole plant. In fact herbicidal high acidity vinegar is one of the alternatives, including some other chemical formulations (Source, Source). Nevertheless the effectiveness and the pricing are huge benefits of glyphosate and it remains one of the major herbicides.
Health Claims
These are only the first three results I am getting on X.
Aside from social media posts, I want to get to the bottom of this. Firstly is it really in humans?
Presence in Humans
Glyphosate has been detected in human urine at concentrations up to 10 ug/L (~10 parts per billion or PPB). Based on environmental exposure (rather than occupational which will be higher) on average it was below 4 PPB, while in areas where aerial spraying is present it goes up to 7.6 PPB (Source). At least it was not found in breast milk. However, these figures seem on the higher end as other studies cite numbers of 0.1 PPB for glyphosate and 0.04 PPB for AMPA (aminomethylphosphonic acid), a major metabolic derivative of glyphosate (Source).
The half life of glyphosate in urine is 5-10 hours (Source), which is relatively fast and similar to the likes of phthalate plasticizers as opposed to “forever” PFAS compounds which take much longer. AMPA is cited to have a half life of 8 hours (Source).
Going back to phthalates (more in my previous post), while they do not present a health risk from accumulation, the constant daily bombardment with those compounds from all the sources around has been shown to lead to endocrine disrupting activity all the while human bodies likely churn through their daily dosage of phthalates in the same day.
The short half life of glyphosate thus most likely indicates that any toxicity related to glyphosate would be caused by continuous exposure rather than its accumulation in the body. That might also mean that it is harder to accurately assess the health impacts as research typically checks for one-off exposures rather than continued impact.
Looking at food diets, soy protein is significantly associated with elevated AMPA, with 37% higher levels for every quartile increase in soy protein consumption (Paper, Section 3).
Research on Health Impact
Turns out the few human health impact studies which exist, show diverging findings in toxicity. However, a meta review of these studies summarizes the following findings (Source paper, p.10-11):
Glyphosate mixed with other ingredients in herbicide formulations typically has higher cell toxicity than pure glyphosate;
Studies showed that higher urinary levels of glyphosate and/or AMPA were associated with breast cancer risk, including 4.5 times higher breast cancer risk in the highest concentration cohort compared to the lowest concentration!
The same underlying cancer focused study (Source) found that breast cancer cases on average had 38% higher AMPA levels than non-cases.
Impact was found on increased levels of oxidative stress biomarkers, endocrine disruption and DNA methylation.
Concentrations vs. Impact
If you read my blog, you probably know that everything always comes down to the question: at what level does it become bad and are we there yet? Because at high concentrations nearly anything can be toxic.
What we know already is that glyphosate is found in human urine in the region of up to 0.06-10 PPB.
We also know that researchers are finding that increased concentrations correlate to increased cancer and endocrine disruption risks.
The cancer-related study had values of AMPA in urine up to 3.6 PPB, but on average under 0.1 PPB (0.06 and 0.08 PPB for cancer and non-cancer cohorts). Given these relatively low quantities I am not entirely sure if:
a) AMPA, derivative of glyphosate, can have health impact at quantities under 1 PPB, which already are routinely found in human urine - meaning it potentially is a risk!
b) or the study results are not accounting for other influencing factors and in the end AMPA is not a major contributor to these health impacts.
Other than the numbers above I could not find a study of direct minimum risk levels (MRLs) for glyphosate / AMPA inside human body. Ideally we want to know for every microgram in urine, what are the increased risks for health issues. Once we know that, we can go back to say how many grams of soy does one need to eat to increase urine concentrations of AMPA.
Gluten allergy
This one is off a tangent, but I saw chatter around glyphosate and gluten allergy on X.
Glyphosate is also used for drying crops. This is relevant for wheat and especially in more damp climates, where using glyphosate increases the quality and uniformity of the crop. One can assume that some of that glyphosate thus stays on the crops in later stages of processing.
Reading into this (Article, MIT study), glyphosate / AMPA were found to disrupt the microbiome and gut health balance. The effect is more pronounced in infants rather than grown ups. In particular reduction in Rothia and Bifidobacteria bacteria species have been found.
In turn the Rothia and Bifidobacteria species are believed to aid the break down of gluten.
So as you see there is a (circumstantial) link as of today, whereby if you eat bread which has glyphosate on it, and that glyphosate inhibits your gluten processing activity at the same time as you are ingesting more gluten in the bread.
And also there is this graph (but beware of the lack of causality link!):
this based on a paper indicating causality, yes
> Impact was found on increased levels of oxidative stress biomarkers, endocrine disruption and DNA methylation.
The other two seem like they could be correlations. Am I reading right that this one has been shown to be causal?