Quercetin and ER+ breast cancer
I'm confused about Quercetin, it seems to have both cancer fighting abilities and tumorigenic effects.
In light of this, would it be at all recommendable for ER+ breast cancer?
I agree, the research on Quercetin and breast cancer isn't clear, especially when it comes to ER+ breast cancer. To be fair, in the rat from 2010, rats were given 2.5g/kg of quercetin in their food for 10 months. The human equivalent dose would be 25.7g/day for a 140lb woman, more than most people would ever take. Also, problems only occurred in rats dosed with high estrogen levels that wouldn’t occur naturally. Basically, the quercetin inhibits COMT, and enzyme involved in estrogen metabolism. If a woman is on estrogen lowering or blocking medication, it is likely not relevant. But even so, I can see how it would make one nervous! https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4006967/
“Quercetin alone did not induce mammary tumors in female ACI rats. However, in rats implanted with E2 pellets, co-exposure to quercetin did not protect rats from E2-induced breast tumor development with 100% of the animals developing breast tumors within 8 months of treatment. Tumor latency was significantly decreased among rats from the quercetin + E2 group relative to those in the E2 group. Catechol-O-methyltransferase (COMT) activity was significantly downregulated in quercetin exposed mammary tissue.”
Then, if you look at other studies, things aren't cleared up.
Here is a study using rat uteri showing different effect depending on dose: https://pubmed.ncbi.nlm.nih.gov/26135605/
Here is a study showing benefit in cell lines for ER NEGATIVE breast cancer cells: https://pubmed.ncbi.nlm.nih.gov/1879042/
And here is a study showing inhibitory effects of quercetin on ER positive breast cancer cells: https://www.nature.com/articles/6690479
Personally, I would consider something else to use to achieve what you are looking for from the quercetin, but others may have a different opinion.
I've opted against it for the same reasons. My tumor was basically 100% estrogen driven. Does anyone know of a natural Aromatase Inhibitor? Was considering Saw Palmetto. It's my understanding that some men use it with prostate cancer.
It looks like Grape Seed Extract is too.