T Nation

Quercitin... Anti-Estrogen or Estrogen?

Dan was wrong. Quercitin is a quite mild estrogen and does
not exert anti-estrogenic action. However, even taken at
fairly large doses (eg 500mg) I don’t think it’s really a
big deal either way. Quercitin’s estrogenic effects are
certainly less than those found in soy. I don’t consider
it to be worth taking, but on the other hand, I think it
would only do minimal harm.

Quercitin is a phenolic compound that is an endothelium-dependent relaxant (present in some red wines and grape juice), probably mediated by its antioxidant properties, increasing NO availability.
It is a mild type II estrogen receptor inhibitor. Whether it would help (or hurt) fat loss is not known, since the type of estrogen receptors in fat cells is not known.

Yes, quercitin is “good” in a health sense. It is an
antioxidant, prevents blood platelets from forming
excessive blood clots, and has demonstrated some
anti-cancer activity. I was refering to it’s bodybuilding
effects. I know several people who have tried quercitin
(including myself) and none of us noticed any real world
(bodybuilding) benefit from taking it. The information I’ve
read led me to believe that it is a mild estrogen agonist -
not and antogonist. But that information could, of course
be incorrect. BTW - quercitin is also found in abundance
in apples and onions.

Quercetin’s most interesting property is its ability to inhibit cytochrome P 450 activity. The potential impact of this is the fact that first pass liver metabolism of many drugs and supplements can be decreased with quercetin intake. When taking oral substances like estrogens, the research shows decreased estrogen metabolism. Theoretically this could be true for testosterone intake as well although I havent seen any data yet on this. Bottom line here, many drugs can be very much more potent with quercetin. Be careful. Quercetin however is a good antioxidant. As far as estrogenic activity, according to the research, there are not any real potent anti-estrogenic effects but on the other hand there are not pro-estrogenic effects either.

Thanks for the info, John. I wasn’t aware of quercitin’s
effect on the cytochrome P 450 enzyme. It sounds like it
has a similar effect on the P 450 enzyme as grapefruit. Is
that right? One might want to be careful not to consume
them both at the same time, especially if taking any drugs.

Actually, grapefruit is high in quercetin and that is why it inhibits P 450. Some have used quercetin alone or grapefruit extract to get some of the same “anti-metabolic” effects.

So, if I take 2 tabs (333mg ea.) of quercitin, during an oral cycle of d-bol,is that good or bad? If good, when is ideal time. And is it really necessary to take quercitin on an empty stomach? And off cycle, what is ideal dosage and time.