Aromatase assumptions

May 2015

An oft-quoted justification for the 'self-evident' safety of glyphosate herbicide is that it interferes with a plant-specific enzyme and therefore won't have any effects on humans.

Glyphosate is widely sprayed on GM crops, most of which have been designed to survive and accumulate it. The weeds around them die because 'aromatase', an enzyme vital to plant protein production, is blocked by the herbicide.

Aromatase enzyme induces 'aromatisation' which means a ring of carbon atoms is formed to produce a new biochemical.

In plants, aromatase acts on amino acids (the building blocks of proteins) to form a class of 'aromatic' amino acids only produced by plants. Animals need aromatic amino acids to build proteins too, but must consume plants (or other animals which have consumed plants) to get them.

The human body, however, also has enzymes with aromatase action (they form a carbon ring). Human aromatase is nothing to do with amino acids or proteins, but acts on the male sex hormone, androgen, to convert it to the female sex hormone, oestrogen. Because our tissues need a precise androgen:oestrogen balance at just the right time for healthy development, most human tissues generate their own specific variant of aromatase.

Plant and animal aromatase would seem to have nothing in common apart from the ability to form a carbon ring. Nevertheless, science is revealing that glyphosate is able to disrupt human aromatase in all sorts of unexpected ways. The herbicide seems able to inhibit androgen activity, oestrogen activity, androgen to oestrogen conversion, and the vital balance between the two hormones.

It has been recognised that glyphosate could attach to some part of the human aromatase/carbon-ring complex because of some small molecular similarity to the plant version. Indeed, the herbicide has been found to interfere with the active site of human atomatase and could be directly obstructing its activity. 

An additional layer to the problem is that cell membranes play a key role in human aromatase function: they control the supply of androgen and its co-factor to the cell, they control the release of the product (oestrogen), they contain binding sites where the aromatase action takes place, and they have receptors which receive the signals controlling the hormone adjustments. 

Glyphosate is always used in a formulation with added detergents which enable it to penetrate through cell membranes. Such detergent action isn't specific to plant cells. The integrity of membranes, including their binding sites and receptors, could well be compromised by the detergents. 

Science has, indeed, shown that glyphosate-based herbicides don't become harmful with increasing dose like regular toxins, but with time are linked to effects consistent with progressive membrane damage: in the short-term, the exposed cells seem to be hyperstimulated, as would happen if nutrients came flooding through a compromised membrane; in the longer term, the cells fail as would happen when toxins find no barrier to entering the cells and their homeostatic mechanisms collapse. 

Besides direct action on the aromatase enzyme and on membranes, it has been established that glyphosate inside cells (courtesy of the detergents which accompany it) causes DNA fragmentation and changes in gene expression. Both androgen and oestrogen function as triggers of gene expression [1], adding significantly to the range of potential metabolic disruption caused by the herbicide.


The only 'self-evident' thing here is that basing safety assents on glyphosate, when most of the problems are caused by the detergents to which it is added is bad science.

Glyphosate can contribute to all manner of unpredictable disturbances in the human physiology. In females this is likely to harm health and fertility, but chronic lack of oestrogen is damaging to males too, especially to bone development. All in all, there could be very serious long-term health problems in a population exposed to glyphosate-based weedkillers.

We really need to know what glyphosate-based formulations are doing to our bodies long-term before we eat or drink any more of them.



  • Céline Gasnier, et al., 2009, Glyphosate-based herbicides are toxic and endocrine disruptors in human cell lines, Toxicology 26
  • Luigi Gennari, et al., 2004, Aromatase Activity and Bone Homeostasis in Men, Minireview, Journal of Clinical Endocrinology & Metabolism, 89(12)
  • Sophie Richard, et al., 2005, Differential Effects of glyphosate and Roundup on Human Placental Cells and Aromatase, Environmental Health Perspectives 113:6

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