T Nation

Drugs Nutrition and Receptor Binding

Hello All-
On the board there is a post discussing flax oil and its estrogen binding capacity. Rather than post my response there, I thought Id post this here for everyone to read because it has implications for much more than flax supplementation.

The question refers to the fact that flax (or componenets of flax seeds/oil) can bind the estrogen receptor (ER). This is true. But before you freak out and start eating lard again in stead of drinking flax, there is an important distinction that must be made when discussing receptor binding. This is important when looking at any compound that binds receptors.
First, there are several types of ligand (binding agent) activity. 1)Agonism means that the ligand (estradiol for example) binds to its receptor and exerts full ER mediated effects. 2)Partial Agonism means that a compound will bind the receptor and only exert a small % of the effects the Agonist would at the same concentration. 3)And then there are Antagonists. a)There are several types. Competitive Antagonists bind the same location and “compete” with the Agonist for the receptor. They prevent Agonist binding. b)There are other types of Antagonists (they are called uncompetitive or noncompetitive) that bind other locations on the receptor to inactivate receptor function so that Agonist can bind but cannot promote any function.

My Point? Well, several things (like flax) can bind the ER and actually have beneficial effects because of either Partial Agonism or Antagonism.
Alone, flax is a Partial Agonist and it can promote very weak estrogenic effects at the receptor. But in the presence of strong estrogens, it prevents binding of the estrogens and and acts as an Antagonist to prevent the full ER mediated effecs.

Ok, enough pharmacology. Practically speaking, from the research, flax does tend to increase LH and T levels. It also may tend to raise estrogen levels in the blood but fortunately there are 2 mechanism that protect us from the estrogen’s effects. First, the flax antagonizes the effects of this raised estrogen level at the receptor. And second, flax tends to increase urinary estrogens (therefore estrogens leave the body faster).

The moral of this story…in the future, remember that just because something binds to a receptor doesnt mean that it promotes the effect of that receptor. It might just do the opposite.

I have a question about phytoestrogens. Should they be avoided in general? I have to admit being woefully uneducated with regards to them. I heard recently that tea is high in phytoestrogens. Could this conceivably be a problem for regular drinkers of tea?

My sentiments exactly! Preach on brotha John! :slight_smile:

As far as phytoestrogens, it all depends on the one in question. Again it all comes back to the ligand (the phytoestrogen) and the receptor and how they interact. There are many compounds that are considered phytoestrogens and not all do the same thing. Some are agonists, some are partial agonists, some are full antagonists, and Id imagine some even promote stronger estrogenic effects than estrogen alone (either due to enhancing the binding of estrogen, to increasing estrogen signalling pathways, or by being stronger at producing an effect than estrogen). Figure out what phytoestrogens you want to know about then we can discuss their effects.

Forgive me for my probable use of improper terms, but does the same logic apply to soy? If it’s a “weak” estrogen and it binds to the ER, would it prevent a stronger estrogen (like estrodiol(?)) from fully activating that receptor?