Is Quercetin Safe To Take?

[Logan-]

Anyone know? I've read very good things about quercetin supplementation. Does anybody know if it's safe to take it for moderate to long term?

ray told me he'd heard good things about quercetin from people

Really? I thought quercetin wasn't liked around here, because of its estrogenic and anti-thyroid effects.


Food Chem Toxicol. 2014 Apr;66:23-9. doi: 10.1016/j.fct.2014.01.016. Epub 2014 Jan 18.

The flavonoid quercetin inhibits thyroid-restricted genes expression and thyroid function.

Giuliani C1, Bucci I2, Di Santo S3, Rossi C4, Grassadonia A5, Piantelli M6, Monaco F7, Napolitano G8.

Author information

Abstract

Quercetin is the most abundant flavonoid present in a broad range of fruit and vegetables. Furthermore, quercetin is available as dietary supplements that are based on its antioxidant, antiproliferative and anti-inflammatory properties. However, concerns have been raised about the potential toxic effects of excessive intake of quercetin, and several studies have demonstrated that flavonoids, included quercetin, can interfere with thyroid function. In a previous report, we showed that quercetin inhibits thyroid-cell growth and iodide uptake. The latter effect was associated with down-regulation of sodium/iodide symporter gene expression. In the present study, we have evaluated the effects of quercetin on the expression of other thyroid-restricted genes, and we show that quercetin decreases the expression of the thyrotropin receptor, thyroid peroxidase and thyroglobulin genes. We further investigated the inhibitory effects of quercetin on thyroid function in vivo through evaluation of radioiodine uptake in the Sprague-Dawley rat, which was significantly decreased after 14 days of quercetin treatment. These data confirm that quercetin can act as a thyroid disruptor, and they suggest that caution is needed in its supplemental and therapeutic use.

Copyright © 2014 Elsevier Ltd. All rights reserved.

KEYWORDS:

Endocrine disruptor; FRTL-5; Quercetin; Radioiodide uptake; Rat; Thyroid

The flavonoid quercetin inhibits thyroid-restricted genes expression and thyroid function. - PubMed - NCBI

I've heard very good things about quercetin too, but stayed away from it because of the impression I've got from here.

Ray did say he’d heard good things about quercetin when I asked him. I almost have qualms about bringing it up Bc it’s not something I think he necessarily put a lot of thought into as an answer. He still recommended thyroid and vitamin d , the usual , and didn’t recommend quercetin or ketotifen but just said he’d heard good things. I think that maybe the estrogenic activity of phytoestrogens can sometimes be weak but the antithyrojd activiry would concern me more. But not a ton of good mast cell stabilizers out there

 

[TeaRex14]

I don't know about long term safety, but I did read the abstract of a study that suggested quercetin is effective at blunting the histamine reaction from a heavy dose of regular niacin.

 

[ecstatichamster]

In my experience, in dosages that actually help allergies, it is highly estrogenic.

 

[BigChad]

In my experience, in dosages that actually help allergies, it is highly estrogenic.

according to this citrus fruits, grapes should be avoided due to the quercetin, apigenin, rutin
Do You Have Hypothyroidism? Find Out Which Foods to Avoid

 

[Motif]

I think my skin symptoms (histamine related) get worse from it. Second day trying and will stop now.

 

[ecstatichamster]

I'm trying 500mg per day now to see what I think. It's been several years since I last tried it, at that time for allergies.

 

[Motif]

I'm trying 500mg per day now to see what I think. It's been several years since I last tried it, at that time for allergies.

Let me know pls

 

[Logan-]

I'm trying 500mg per day now to see what I think. It's been several years since I last tried it, at that time for allergies.

Let us know about your experience. Quercetin supposedly has strong anti-inflammatory effects, I am curious.

 

[iso1]

Quercetin is thyroid supressing.

 

[LauriePartridge]

Quercetin is thyroid supressing.

I agree. There was a 2014 study that showed it is a thyroid disrupter and advised to use caution when supplementing. It definitely gives me estrogenic/hypo symptoms.

 

[Pistachio]

Anyone know? I've read very good things about quercetin supplementation. Does anybody know if it's safe to take it for moderate to long term?

I've successfully treated anaphylactic shock with quercetin (by accident). Amazing substance. I am not saying it can replace auto-injectors for everyone, but it has worked in my experience. What else can it do?

Warning: prolonged, daily use can lead to severe insomnia (this happened to me).

 

[miquelangeles]

I never felt any benefits from quercetin, maybe the opposite. It might depend on the manufacturer and the method of extraction, but I wouldn't be surprised if most of them have contaminants. In high doses it causes DNA damage or interferes with DNA repair mechanisms. I wouldn't supplement more than 50-100mg/day and I'd be cautious about other isolated flavonoids as well. They are not the same as food. The naringenin and naringin in orange juice are just as good, and they too prevent histamine release, and there's quercetin in orange juice as well, approximately 10mg/liter; the peels probably contain even more. Yasmina from healing histamine com died from an aggressive and accelerated form of breast cancer. She had blamed it on exposure to chemical weapons during her years in Iraq as a journalist, but she was also supplementing high doses of isolated flavonoids - quercetin, rutin, luteolin, curcumin, most of them proprietary formulations - and who knows whether this had anything to do with it as well or not. Some lesser known rich sources of quercetin are lovage, dill, and the dry outer scales of brown onion which are the richest known source of free quercetin - in other plants quercetin is found as glycosides only. Onion peel tea is a traditional remedy very effective for cough and colds.

 

[Dr. B]

I agree. There was a 2014 study that showed it is a thyroid disrupter and advised to use caution when supplementing. It definitely gives me estrogenic/hypo symptoms.

isnt it in orange juice? just small amounts maybe or the sourcing?

 

[LauriePartridge]

The flavonoid quercetin inhibits thyroid-restricted genes expression and thyroid function - PubMed That's the link to the study. (I see now it was originally posted so sorry for the duplicate information.)

Flavonoids are thyroid disrupters. There is a lot of research showing how they interfere with thyroid function:

Impact of flavonoids on thyroid function - PubMed

Flavonoids are polyphenolic compounds of natural occurrence produced by plants that are largely consumed both for therapeutic purposes and as food. Experimental data have shown that many flavonoids could inhibit thyroperoxidase activity, decreasing thyroid hormones levels thus increasing TSH and...

pubmed.ncbi.nlm.nih.gov

Orange juice doesn't really have that much Quercetin in it like 1 mg per 100 ml:

Showing all foods in which the polyphenol Quercetin is found - Phenol-Explorer

Database on Polyphenols in Foods

phenol-explorer.eu

I think small amounts are ok and the thyroid can probably handle it if it's functioning well. But I don't think it's a good idea to eat or consume large amounts.

 

[Badger]

I never felt any benefits from quercetin, maybe the opposite. It might depend on the manufacturer and the method of extraction, but I wouldn't be surprised if most of them have contaminants. In high doses it causes DNA damage or interferes with DNA repair mechanisms. I wouldn't supplement more than 50-100mg/day and I'd be cautious about other isolated flavonoids as well. They are not the same as food. The naringenin and naringin in orange juice are just as good, and they too prevent histamine release, and there's quercetin in orange juice as well, approximately 10mg/liter; the peels probably contain even more. Yasmina from healing histamine com died from an aggressive and accelerated form of breast cancer. She had blamed it on exposure to chemical weapons during her years in Iraq as a journalist, but she was also supplementing high doses of isolated flavonoids - quercetin, rutin, luteolin, curcumin, most of them proprietary formulations - and who knows whether this had anything to do with it as well or not. Some lesser known rich sources of quercetin are lovage, dill, and the dry outer scales of brown onion which are the richest known source of free quercetin - in other plants quercetin is found as glycosides only. Onion peel tea is a traditional remedy very effective for cough and colds.

"dry outer scales of brown onion which are the richest known source of free quercetin."

I don't think so, not true. Capers are richest source of quercetin. "But by far the richest source of quercetin is capers. Although they look like berries, capers are actually tiny flower buds that grow on shrubs throughout the Mediterranean region. According to data collected by the USDA, raw capers provide 234 milligrams of quercetin per 100 grams (3.5 ounces). Canned capers in brine — as they are commonly eaten — provide 173 milligrams of quercetin. In comparison, 3.5 ounces of raw onions provide 39 milligrams, and the same amount of boiled asparagus has 15 milligrams, according to the USDA."

Foods With the Highest Content of Quercetin

Foods With the Highest Content of Quercetin | Livestrong.com

Top quercetin foods include capers, onions, asparagus and apples. Although not yet proven, quercetin may help prevent diseases caused by oxidative stress.

www.livestrong.com

 

[rr1]

Z-Stack®

Z-Stack is based on Dr. Zelenko's years of extensive published scientific research – and now made available to you. Enjoy free shipping for all US orders.

zstacklife.com

This is Vladimir Zelenkos product, he and his team have treated millions of C0youknowwhat patients with this. Quercetin is a zinc ionophore, which means it helps to get Zinc into the cell to stop viruses replicating.

 

[miquelangeles]

"dry outer scales of brown onion which are the richest known source of free quercetin."

I don't think so, not true. Capers are richest source of quercetin. "But by far the richest source of quercetin is capers. Although they look like berries, capers are actually tiny flower buds that grow on shrubs throughout the Mediterranean region. According to data collected by the USDA, raw capers provide 234 milligrams of quercetin per 100 grams (3.5 ounces). Canned capers in brine — as they are commonly eaten — provide 173 milligrams of quercetin. In comparison, 3.5 ounces of raw onions provide 39 milligrams, and the same amount of boiled asparagus has 15 milligrams, according to the USDA."

Foods With the Highest Content of Quercetin

Foods With the Highest Content of Quercetin | Livestrong.com

Top quercetin foods include capers, onions, asparagus and apples. Although not yet proven, quercetin may help prevent diseases caused by oxidative stress.

www.livestrong.com

Dry outer scales of brown onion have 10 grams of quercetin per 100 grams.
The root of brown onion has 16 grams of quercetin per 100 grams. That's 80 times more than raw capers.

 

[Dr. B]

Z-Stack®

Z-Stack is based on Dr. Zelenko's years of extensive published scientific research – and now made available to you. Enjoy free shipping for all US orders.

zstacklife.com

This is Vladimir Zelenkos product, he and his team have treated millions of C0youknowwhat patients with this. Quercetin is a zinc ionophore, which means it helps to get Zinc into the cell to stop viruses replicating.

those dosages are insane mate especially the quercetin... even zinc vitami c is high
even a half dose is high

 

[Homo Consumericus]

those dosages are insane mate especially the quercetin... even zinc vitami c is high
even a half dose is high

None of those doses are high. Nothing about the Zelenko protocol is "insane." His success rate speaks for itself.

 

[Dr. B]

None of those doses are high. Nothing about the Zelenko protocol is "insane." His success rate speaks for itself.

vitamin d3 is a good dose,
that combination of vitamin C and zinc will cause copper depletion and probably other issues.
the protocol might be acceptable as a temporary anti viral protocol. but otherwise, those vitamin C dosages, and the zinc are very high. oysters have zinc and iron in a 1:1 ratio alongside copper and other nutrients, so 30mg zinc from oysters wont have the same effects as a supplement. vitamin C is usually made using corn mold, and causes issues in many people. you would need a ton of orange juice to get that much vitamin C, and it wouldnt work the same as a supplement.
the quercetin is the most dangerous part, and craziest dosage. how many orange peels would you need for 500mg quercetin, like 200 or more? and they would still probably have other nullifying factors