Talk:Quercetin/Archive 1

Heading
Please do something about the spelling of flavonoid, in the title and first paragraph there are three different renditions of the word. —Preceding unsigned comment added by 134.148.4.14 (talk) 03:24, 14 February 2009 (UTC)

This is on the list of IARC Carcinogens in Group 3, meaning that its carcinogenicity can't be determined in humans or that insufficient info exists on its carcinogenicity in humans. That always seemed odd to be, given how much its anticancer properties have been discussed. Does evidence exist that it is, in fact, a carcinogen? Such information should be included if it does exist and is reliable.

Quercetin has an LC50 of about 0.0001 Molar meaning to high a concentration kills normal cells. I have heard nothing about it causing cancer. I am not a formal expert in this field.

Topical Absorption using Ultrasound
The british journal said "Quercetin is a small and slightly lipophilic molecule (molecular weight=302 Da, octanol-water partition coefficient, Ko/w~1.2±0.13 (Brown et al, 1998)) and is expected to diffuse across cell membranes at a high rate."

It appears that the ultrasound doesn't increase absorption (in this case) but that something else is involved. The article suggest something about a cellular stress response. We need a source on the statement about ultrasound increasing the absorption. Unless someone convinces me otherwise, in the future I might edit this article.


 * If you are going to include what quercetin and ultrasound do, it needs to mention what ultrasound does alone (or with other substances)(i.e. the control)...it's analogous to saying that peppermint + cisplatin has a strong effect against certain tumors...anything + cisplatin will have a strong effect on those tumors.  That doesn't demonstrate that the "anything" here has had any effect.  If ultrasound alone has no effect, it should be mentioned.  (Also, the definition is too generic...I don't know anything about quercetin, so I don't know what's special about it, but whatever is, perhaps it should follow "Quercetin is a flavinoid that..." Mauvila (talk) 20:46, 8 March 2008 (UTC)

FRS Healthy Energy
There's a new product - FRS Healthy Energy - where the main ingredient is Quercetin. It is meant to boost energy (naturally). Any opinions? I'm always a bit skeptical about products like this. —Preceding unsigned comment added by 76.187.71.27 (talk) 11:44, 10 March 2008 (UTC)


 * Skepticism is a good thing. While quercetin (250-325mg) is the main ingredient in FRS, it also contains many other ingredients. So, the effects of the product cannot be entirely attributed to quercetin. However, their claim that the FRS products can act as antidepressants may have some legitimacy, related to the quercetin content. This would be assuming that you're consuming other xenobiotics which have antidepressant properties. (These are metabolized by cytochrome P3A4, which metabolizes many different drugs.) Such xenobiotics may be present in FRS products. As for increased energy and such - FRS products contain caffeine and ginseng extracts (the same two ingredients found in the vast majority of energy drinks). So, overall... I wouldn't waste your money on this product - from what I've seen, it's exorbitantly expensive. You could, however, purchase quercetin itself for a reasonably low price, and see if it has any effect on its own. But as I've said, if you're taking any other drugs, use quercetin with caution or avoid it entirely. Fuzzform (talk) 17:42, 22 March 2008 (UTC)

I'm also skeptical of "dietary supplements," which includes a lot of fraud. However, George Lundberg, the editor of JAMA, said that we must go with the evidence. I'm willing to see their evidence.

The founders of FRS certainly have respectable credentials. According to their web site,

FRS was invented by a team including Dr. Mitsunori Ono, PhD as a fatigue fighting and general health drink. It was then tested and refined by Dr. Lan Bo Chen, PhD and Dr. Mitsunori Ono, PhD, who at the time were both researchers at Harvard University.

Dr. Marcus Elliott, MD - Advisor • Harvard Medical School MD • Professional and Olympic Athlete Trainer Read more about Dr. Marcus Elliot on his website

Dr. Lan Bo Chen, PhD - Advisor • Professor at Harvard Medical School • Formerly worked at Dana-Farber Cancer Institute

Dr. Mitsunori Ono, PhD - Inventor, Advisor • Author of more than 65 academic publications and over 45 U.S. patents • Formerly a Visiting Professor at Harvard Medical School

I don't care whether quercetin is good or bad. I'll go with the evidence. Nbauman (talk) 22:32, 13 February 2009 (UTC)


 * None of the above is evidence. Don't put it beyond a Harvard MD to exaggerate claims when a lot of money is at stake.
 * I'm interested in effects on energy and fatigue. There actually does appear to be some evidence, albeit in rats or cancer patients or in athletes for a week, that quercetin has an effect. If I had to bet, I'd say it's snake-oil like 5-hour energy. I'll add references as I find them. Feel free to clean up or reorganize. --128.112.66.17 (talk) 01:25, 25 July 2009 (UTC)

5-hour energy is just caffeine, so yeah it's marketing. — Preceding unsigned comment added by RenagadeSci (talk • contribs) 18:54, 13 July 2011 (UTC)

Research on alleviating disease
Zefr, I reverted your change because it didn't give a source for its claim that "there is no evidence for such actions from human population studies. There exists no research in humans proving an effect of flavonoids or quercetin for alleviating cancer or any disease." There was evidence in the source I cited (although I messed up the Wiki citation to PubMed so it didn't come out right).

Neuhouser at Fred Hutchinson Cancer Research Center, said, "There is consistent evidence from these studies that flavonoids, especially quercetin, may reduce the risk of lung cancer. Further research using new dietary databases for food flavonoid content is needed to confirm these findings before specific public health recommendations about flavonoids can be formulated."

That's not "no research." If you do want to say there is "no research," then according to Wikipedia rules you have to find a WP:RS to support it. I don't think you'll find one.

The research doesn't prove anything, at Level 1 standards of evidence, but that's not the point. Most research doesn't meet the Level 1 standard of proof.

There are doctors who recommend it, whether they're right or wrong.

And it is used as a nutritional supplement, whether it does any good or not.

Agree? Disagree?

If you want to rephrase my introduction, that's fine, as long as you can support it with WP:RS.

(BTW, I saw quercetin advertised in the Wall Street Journal, no less. I thought it was bullshit so I checked it out. I was surprised to find out that there was some legitimate research supporting it. I'm generally skeptical of so-called "nutritional supplements" and alternative medicine, but as George Lundberg said, if they have the supporting evidence, we have to give them their due. And quercetin does have supporting evidence. It's not level 1 evidence, but neither is most dietary advice, even in academic medicine. In the post-paternalistic era, most doctors recommend skepticisim, giving the patient the facts, and letting the patient decide.) Nbauman (talk) 15:54, 9 February 2009 (UTC)


 * This is the FDA reference providing nutritional claims concerning cancer, http://www.cfsan.fda.gov/~dms/qhc-sum.html where quercetin is not displayed which means it has not yet reached the stage of FDA evaluation for health claims.

The research on quercetin is very preliminary, as it is only in pilot studies of clinical research. The reference you provide by Neuhouser does not imply prevention of cancer or other diseases. It simply says it may reduce the risk -- quite a different message, and one deemed "safe" for suggesting research progress without committing to a conclusion.

The introductory sentence and second paragraph for the article are misleading and scientifically incorrect
 * has not been shown to prevent cancer or any disease
 * high intake has not been shown to reduce cancer
 * scientists have not specified flavenoids (sic --"flavonoids") as responsible for any biological mechanism in vivo
 * there is no population study showing any conclusive anti-disease effect
 * no respected physicians (MDs, not naturopaths) or expert scientists would claim flavonoids protect against cancer. No such evidence has been provided and no such claim is approved by the FDA. In fact, it is against the law to publicly infer such effects on a product label.

--Zefr (talk) 04:33, 10 February 2009 (UTC)


 * Zefr, I don't quite understand what your objection is. Do you disagree with this sentence?


 * Quercetin is a flavonoid, specifically a flavonol, and is used as a nutritional supplement to prevent cancer and other diseases.
 * Nbauman (talk) 23:08, 10 February 2009 (UTC)

Yes, that sentence would lead a lay user of Wikipedia to believe that it is a fact quercetin can prevent cancer and other diseases. There is no scientific evidence that this is true for humans -- maybe in test tube disease models, but not in experimental animals or humans. And certainly not compliant with FDA guidelines.

To avoid confusion and state facts accurately, I revised the opening sentence and 2nd paragraph two days ago -- reverted by you to the inappropriate information presently in the article. --Zefr (talk) 23:33, 10 February 2009 (UTC)


 * I was paraphrasing a peer-reviewed article by an investigator at the Fred Hutchinson Cancer Research Center, which is a WP:RS.


 * Is that sentence true? Quercetin is a flavinoid, right? And it is used as a nutritional supplement, right? Nbauman (talk) 04:15, 11 February 2009 (UTC)

The paraphrase as a whole is inaccurate. It has three components:

1) quercetin is a flavonol type of flavonoid, so you are correct (the vowels in the word are important to be correct -- there are closely spelled but chemically distinct types of flavonoids; see http://en.wikipedia.org/wiki/Flavonoid#Biosynthesis);

2) quercetin is a dietary supplement (so you are correct) but, like all dietary supplements, is not regulated by the FDA (no petitions have been submitted for health claims because the research has been inadequate);

and 3) quercetin does not prevent cancer or any disease. This statement should be made because the research to prove disease prevention has not been done.

If you were to ask Neuhouser or any bona fide scientist about the status of disease prevention by quercetin, the answer would unequivocally be that
 * research is preliminary at best
 * there is no evidence for disease prevention or even knowledge of its specific action in the human body and
 * it would not be recommended to any patient with cancer or another disease as it misleads that person to think quercetin might be more effective than a prescribed drug. This is where misinformation becomes dangerous and the FDA would step in to stop such claims if made on a product label.

Our standards at Wikipedia should be on the side of safety and should be guided by where a candidate therapeutic stands in the evaluation process of the FDA. That is why I provided the link to the FDA guidance,http://www.cfsan.fda.gov/~dms/qhc-sum.html and that is why the article should be reinstated to the edits I made. --Zefr (talk)


 * OK, you agree with


 * Quercetin is a flavonoid, specifically a flavonol, and is used as a nutritional supplement.


 * Neuhauser wrote


 * There is consistent evidence from these studies that flavonoids, especially quercetin, may reduce the risk of lung cancer. Further research using new dietary databases for food flavonoid content is needed to confirm these findings before specific public health recommendations about flavonoids can be formulated.


 * Do you agree with that? Nbauman (talk) 17:54, 11 February 2009 (UTC)

Yes, but Neuhouser's conclusion does not say that quercetin prevents cancer and other diseases as stated currently. That is incorrect and misleading.

He does give cautious language that more research is needed before specific public health recommendations about flavonoids can be formulated. This is consistent with FDA regulations and is the appropriate context as a reference -- it would be fine as the WP:RS. Why not use his language in the opening sentence?

The second paragraph needs to be revised to more cautious language. --Zefr (talk) 19:43, 11 February 2009 (UTC)


 * Neuhouser says there is "consistent evidence" that quercetin "may reduce the risk of lung cancer," and further research is necessary to confirm it. Do you agree with that? Nbauman (talk) 20:19, 11 February 2009 (UTC)

Try re-writing the first two paragraphs and post them here first so anyone can debate them. The more important part of Neuhouser's comment is "Further research ... is needed to confirm these findings". I would not agree there is consistent evidence for quercetin to reduce cancer risk since that applies mostly to in vitro studies. The in vivo animal results are not very convincing and there is no evidence quercetin is important in people. --Zefr (talk) 23:54, 11 February 2009 (UTC)


 * I already wrote it and I think they're fine, although I'm open to suggestions, criticism and disagreement. I'm debating it here. Go ahead and debate it.


 * Your changes violated WP rules for reliable sources, neurtral point of view, and no original research, among others.


 * Marian Neuhouser is a PhD and investigator at Fred Hutchinson Cancer Research Center with 75 publications, many of them in major journals. She's a reliable source. She thinks that there is "consistent evidence" that quercetin "may reduce the risk of lung cancer." You're an anonymous Wikipedia editor. She says there is consistent evidence from human populations. You say there isn't. Why should anyone believe that she's wrong and you're right? What published evidence do you have to support your opinion? That's the way science works. You can't change it without a WP:RS. Nbauman (talk) 03:08, 12 February 2009 (UTC)

Present opening

Quercetin is a flavonoid, specifically a flavonol, and is used as a nutritional supplement to prevent cancer and other diseases.

High dietary intake is associated with reduction in cancer, and scientists suspect flavenoids may be responsible. Research shows that flavanoids influence cellular mechanisms in vitro and in animal studies, and there is limited evidence from human population studies. Some doctors recommend flavenoids for cancer prevention, while others say that the evidence so far is insufficient.

Revised

Quercetin is a flavonoid, specifically a flavonol, used as a nutritional supplement with intent to prevent cancer and other diseases. Although in vitro evidence exists for such possible effects, few studies in animals and none in humans have demonstrated anticancer activity.

Further, as quercetin itself may be a carcinogen, human safety studies are needed before interventional clinical trials are conducted on patients with cancer. As there exists no research in humans proving an effect of quercetin or any flavonoid for alleviating cancer or any disease, the FDA has not included quercetin among dietary therapeutics approved with qualified health claims.

--Zefr (talk) 10:21, 12 February 2009 (UTC)


 * I don't follow you. You say, "few studies in animals and none in humans have demonstrated anticancer activity[1]"


 * But the very citation you give, Murakami, says, "epidemiological studies have indicated that an intake of quercetin may be associated with the prevention of lung cancer."


 * The significant fact is that we've found 2 researchers, including your own source, who say that epidemiological evidence indicates that quercetin may prevent lung cancer. So we have good WP:RS authority to say that it may prevent cancer. That's the science.


 * They haven't established certainty, but they don't have to. Epidemiological studies never establish certainty.


 * Moreover, you should review WP:OR to see what you can and can't say on WP. It's OK for you to cite Verschoyle as saying that quercetin is a suspected carcinogen and shouldn't be used in the healthy population. It's not OK for you to write the article to say that, because WP has to be WP:NPOV. Different doctors disagree, and just because Verschoyle says so, that doesn't mean it's true. Furthermore, WP doesn't give medical advice. A WP article can't recommend or urge people to take or not take quercetin. All we can do is give both sides and let them decide.


 * We have to give the views of Neuhouser, Murakami, and Verschoyle, and we are not competent to decide who is right. Nbauman (talk) 10:53, 12 February 2009 (UTC)

It would help if you familiarized yourself with this, particularly the section beginning, For example, cancer is a constellation of more than 100 different diseases and the following section on Intervention Studies.

Then read Part D., Evaluating Human Studies and Part G., Assessing Significant Scientific Agreement (SSA) -- the conclusion that will convince you that quercetin has insufficient evidence to be stated that it prevents cancer.

There is no successful intervention study of quercetin on cancer patients and no confirmation of SSA; therefore, there is no proof that quercetin prevents cancer.

Revised

Quercetin is a flavonoid, specifically a flavonol, used as a nutritional supplement with intent to prevent cancer and other diseases. Although in vitro evidence exists for such possible effects, few studies in animals and none in humans have proved anticancer activity. In preclinical research, quercetin remains among the most intensively studied flavonoids as a potential therapeutic agent.

However, because quercetin itself may be a carcinogen, human safety studies are needed before interventional clinical trials are conducted using quercetin for cancer patients. As no such research in humans has been done to prove safety and efficacy of quercetin or any flavonoid for alleviating cancer, the FDA has not included quercetin among dietary therapeutics approved with qualified health claims.

--Zefr (talk) 17:18, 12 February 2009 (UTC)


 * Your cites on carcinogenicity are very interesting and should go into the entry.


 * The FDA "Qualified Health Claims" document that you cite is also very interesting, and probably should go into a WP entry on dietary supplements if it's not there already.


 * However, the FDA document says nothing about quercetin. As I understand it, the absence of a product on that list means that the FDA has made no judgment on the product, neither favorable nor unfavorable. It doesn't indicate anything about the product's safety or efficacy. Nbauman (talk) 20:37, 13 February 2009 (UTC)


 * Zefr, Neuhouser and Murakami (your own source) have published their opinion that quercetin may reduce the risk of lung cancer. You still haven't explained how you can ignore them. That's a reliable statement, according to WP:RS. It belongs in the entry, unless you can come up with a good reason for keeping it out.


 * For you to say that none of the research has "proved" anticancer activity is WP:OR. Nobody made the claim that it was proved. You can't put that in WP.


 * Some reliable, published, peer-reviewed sources say it "may" prevent lung cancer. That's pretty strong evidence. Why do you think you're justified in taking that out? Nbauman (talk) 01:19, 15 February 2009 (UTC)


 * While a study may suggest that flavinoids (like quercetin) may reduce one's risk of getting cancer, it's not a particularly meaningful fact. There are so many factors that influence one's risk of getting cancer (e.g. genetics, radiation exposure, exposure to other carcinogens, intake of anti-cancer substances, etc.), that consuming flavinoids will likely have no meaningful effect on one's risk of getting the disease. Thus, saying that quercetin or a like substance will reduce one's risk of getting cancer is misleading. Everything else being static, yes, querectin may reduce one's risk. But, of course, in the real world, other variables aren't static. Quercetin only reduces one's risk in a meaningful way if other the variables don't exist or don't change. Without the proper caveats, these additions to this article don't give the full picture (at best) or are horribly misleading (at worst). ask123 (talk) 22:09, 9 February 2010 (UTC)

Drug Interactions
Does its bind to DNA gyrase occur in blood? That is to say, would it bind when consumed by humans to their DNA, or would the cell's membrane prevent the interaction? —Preceding unsigned comment added by C lawnmower (talk • contribs) 20:56, 23 March 2009 (UTC)

Increased energy expenditure
Can somebody clarify the second paragraph? That is, does the research only cover eight weeks, or does it show loss of efficacy after eight weeks? Washod (talk) 15:49, 4 August 2009 (UTC)


 * It's the latter I believe. And, also, it was only shown in mice. It may not apply to humans. ask123 (talk) 22:20, 9 February 2010 (UTC)

Fruits & vegetables are associated with "reduction in cancer"?!
I added the tags to the sentence that claims that intake of fruits and vegetables is associated with a reduction in cancer. (I wasn't signed in at the time.) First of all, what does "reduction in cancer" mean? An individual either has it or doesn't. Is the editor speaking of cancer in a population? Second, regardless of this ambiguity, the claim is dubious. There are no reliable studies that show that eating fruits or vegetables will cause a person to avoid cancer. It just ain't true. Eating fruits and vegetables can help -- along with a host of other positive habits. But there is no pure, causal relationship here. There are too many variables here for the consumption of flavonoids to stand out meaningfully. ask123 (talk) 21:51, 9 February 2010 (UTC)


 * Is this true?! Eating fruits and veggies doesn't reduce your cancer risk? Can any experts chime in? Hanxu9 (talk) 22:51, 3 March 2010 (UTC)


 * The key words are "may reduce the risk", as used by the FDA for health claim statements on food labels. See 21 CFR 101.76 and 21 CFR 101.78. I have revised the article to include this reference.--Zefr (talk) 00:47, 4 March 2010 (UTC)

CYP3A4 inhibitor or inducer?
The Drug Interaction section says:

Quercetin is also a potent inhibitor of CYP3A4


 * Further research suggests that the cited paper incorrectly refers to Quercetin as a CYP3A4 inhibitor. Refer to Drug interactions due to cytochrome P450 (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1312247/), which states "Coadministration of cyclosporine with a CYP3A4 inhibitor decreases an individual's CYA dosage requirement.". Compare this to the quote from the cited text, above, "Quercetin significantly decreased cyclosporin oral bioavailability". If Quercetin was a CYP3A4 inhibitor, then cyclosporin oral bioavailability would have been increased, not decreased.

--JoeSperrazza (talk) 20:30, 15 June 2010 (UTC)

However:


 * Different references (see http://dmd.aspetjournals.org/content/31/5/533.full and http://dmd.aspetjournals.org/content/31/5/533/F4.expansion.html, for example) discuss quercetin as one of several CYP3A4 inducers.


 * The difference between a CYP3A4 inducer and inhibitor is significant. Inducers increase clearance and reduce bioavailability of certain drugs, such as Tarceva; inhibitors decrease clearance and increase toxicity of those same drugs.


 * There are other references that list quercetin as one of the CYP3A4 inducers, e.g.,


 * http://www.ncbi.nlm.nih.gov/pubmed/16442130 "...long-term exposure of herbal agents (hyperforin, kaempferol and quercetin) showed enhanced expression of CYP3A4..."


 * However, in addition to the original reference, there are others that list quercetin as a CYP3A4 inhbitor:


 * http://www.ualberta.ca/~csps/JPPS4(3)/S.Wanwimolruk/grapefruit.htm Inhibition of human CYP3A4 activity by grapefruit flavonoids, furanocoumarins and related compounds. "The results showed that the inhibition of quinine 3-hydroxylation (CYP3A4 activity) by bergapten (67%), and quercetin (55%) was greater than naringenin (39%) and naringin (6%), at the same inhibitor concentration of 100 M."


 * http://www.psa.org.au/site.php?id=745 The role of CYP3A4 and p-glycoprotein in food-drug and herb-drug interactions. "in vitro experiment, acute exposure of hyperforin is a potent competitive inhibitor of CYP3A4, and quercetin a moderate inhibitor of CYP3A4"

I suggest that the article should be updated to note that sources offer conflicting information regarding quercetin and CYP3A4 inhibition and inducement.

--JoeSperrazza (talk) 14:50, 15 June 2010 (UTC)


 * I'm not sure anyone is reading these comments, but, for the record, I recommend changing the paragraph in question to this:


 * Quercetin is described as an inhibitor of CYP2C9 . Sources are inconsistent as to whether Quercetin is an inhibitor or inducer of CYP3A4. CYP2C9 and CPY3A4 are members of the cytochrome P450 mixed-function oxidase system, and as such are enzymes involved in the metabolism of xenobiotics in the body. In either case, quercetin would be expected to alter serum levels, and therefore effects, of drugs metabolized by these enzymes.


 * JoeSperrazza (talk) 22:23, 21 June 2010 (UTC)

There is no contradiction between sources. CYP enzymes generally exist to break stuff down, but it's a messy process involving oxygen, one of the worst behaved players in the biochemical game. If you try to use a CYP enzyme, two things are likely to happen: a) you will inhibit it, as the miscellaneous compound and oxygen mix end up doing bad things to the enzyme; and b) you will likely induce it, if the liver has a working feedback mechanism in place to sense the use/abuse of that particular CYP. Note that an inducer is not an agonist. Wnt (talk) 19:28, 1 June 2011 (UTC)

Paclitaxel and quercetin
AHFS Drug Information (2010) identifies quercetin as an inhibitor of CYP2C8, and specifically names it as a drug with potential to have harmful interactions with paclitaxel. Since paclitaxel is metabolized primarily by CYP2C8, it seems reasonable to expect that taking quercetin with paclitaxel would lead to increased bioavailability of paclitaxel (and several studies have shown this in animal models and human hepatocyte models ). Depending on the amount of quercetin ingested and the degree to which CYP2C8 is inhibited, this could substantially decrease the dose of paclitaxel at which toxic side-effects begin to occur. There haven't been any human clinical trials to investigate the question as far as I can tell, but it's not exactly the sort of thing that could be done ethically, given that the expected outcome is increased toxicity.

Anyway, I think this information is particularly relevant to the paragraph about the purported anti-cancer effects of quercetin and should be added as a warning note near that paragraph, as paclitaxel is a fairly common component of antineoplastic therapy. Anyone looking for information on Wikipedia about alternative/natural remedies for cancer ought to know that if they're already taking paclitaxel, adding quercetin to their diet probably isn't a good idea. —Preceding unsigned comment added by 76.30.172.128 (talk) 23:19, 12 October 2010 (UTC)

Here are the references, since apparently I'm a Wikinewb:

1. Drug interactions of paclitaxel metabolism in human liver microsomes. Bun SS, Ciccolini J, Bun H, Aubert C, Catalin J. J Chemother. 2003 Jun;15(3):266-74.PMID: 12868554

2. Effect of several compounds on biliary excretion of paclitaxel and its metabolites in guinea-pigs. Bun SS, Giacometti S, Fanciullino R, Ciccolini J, Bun H, Aubert C. Anticancer Drugs. 2005 Jul;16(6):675-82.PMID: 15930897 —Preceding unsigned comment added by 76.30.172.128 (talk) 23:25, 12 October 2010 (UTC)


 * ✅ Wnt (talk) 20:42, 1 June 2011 (UTC)

Reorganization
I've done some extensive reorganization to the article. I think it's crucial when dealing with tentative research findings to do as good a job of organizing the article as we can, so that the loose bits of data have a better chance to congeal and provide context for each other. Please let me know if anything seems out of place. Wnt (talk) 20:58, 1 June 2011 (UTC)

Alternative medicine
Someone deleted my reference to an Alternative Medicine Review article, and text stating that it had been described as comparable to cromolyn sodium. I think it is important not to exclude alternative medicine; the article should cover all aspects of the compound. Actually, the alternative medicine article, with a modest number of references, was making the very plausible argument that it has the same effect as another plant chemical, cromolyn, with a rather similar structure (but missing a ring, and dimerized). It is actually a much more scientific argument than the typical "antioxidants are good, they must scrounge up oxygen radicals and stop aging, cancer and the heat death of the universe" sort of argument we see stated or implied in an appalling number of mainstream science publications. Wnt (talk) 18:48, 6 June 2011 (UTC)
 * I don't think this particular journal meets requirements for WP:MEDRS. Previous reviews I have seen published there have been clearly pushed fringe/quack remedies (i.e. using chelation to treat autism), and this probably falls under the description in WP:PARITY about nominal peer review, but only by true believers in alt med.   This article clearly needs more work - probably by the removal of content sourced only to primary studies and replacing what we can with secondary reviews (as per MEDRS); we do not make the situation better by adding poor sources like the one you are suggesting. Yobol (talk) 19:35, 6 June 2011 (UTC)
 * I loathe that obstructionist guideline with a passion, but secondary articles in journals are one of the few things it doesn't ban. It comes up in a search at NCBI, which must mean something.  I should point out that the legendary "patterned water" study was published in Nature, so you can't knock a whole journal just because of a single slip-up.  And if you are truly convinced that "alternative medicine" is not medicine, then WP:MEDRS does not apply!  (and there was much rejoicing)  But seriously - your health insurance probably pays for alternative medicine, your hospital probably offers it - don't you think we ought to be allowed to talk about it?  Especially when the argument that they make is so straightforward and sensible. Wnt (talk) 23:35, 6 June 2011 (UTC)
 * Not a single slip up, multiple reviews I've seen have dubious information in them, or cherry pick data to support the use of CAM interventions; discussions of medical problems will overwhelmingly discuss positive findings of CAM interventions while noting any and every drawback of conventional medical treatments for the same medical problems. This shows a distinct bias towards promoting CAM ideas and interventions, and therefore is not the type of independent source we should be using here on Wikipedia.  Their editorial board has more naturopaths than medical doctors (or DOs) on it - remarkable for a standard medical journal, not so much for a one that consistently promotes CAM.  As far as I'm concerned, it falls under the WP:PARITY guideline of being not being generally reliable, based on my experience looking at their work and at their review process.  What insurance companies do or do not pay for has no bearing on what is reliable on Wikipedia.  That a journal is MEDLINE indexed is also not a guarantee that it is reliable - the journal Homeopathy is likewise indexed in MEDLINE but is not considered reliable, either.  I don't have a problem talking about alternative medicine, I just want to use reliable sources to do so. Yobol (talk) 01:15, 7 June 2011 (UTC)
 * Do you deny that it has editorial control? Do you deny that it expresses what the naturopaths think?  I tried to word it to make it clear I was describing an alternative medicine viewpoint.  Wnt (talk) 05:04, 7 June 2011 (UTC)
 * I think the review would only be reliable for what the authors of the review think; the other question is how much WP:WEIGHT we should give it, as it is to me a WP:FRINGE general alt med view at best and fringe view of the authors at worst. I don't think speculation in an alt med advocacy journal should be given any weight; and if it is more than just idle speculation, it would be published in a more reliable source, in which case we wouldn't need to use this source anyways.  That is why it is important to use good sources; presentation in a high quality secondary source denotes that particular piece of information deserves weight. Yobol (talk) 05:32, 7 June 2011 (UTC)

Is there still a link to the journal article? I'd be interested to see what it says. Also, comparing quercetin and cromolyn's structure and saying that they have a 'similar structure (but missing a ring, and dimerized)', is rather wild. Those two chemical modifications can have massive outcomes on a compound's bioactivity.Markwdck (talk) 09:55, 15 November 2011 (UTC)

Preliminary research
Rather than populating the Article with preliminary research, conjecture and speculation, let's vet it here first, as in this draft entered yesterday by Duche831 -- --Zefr (talk) 03:58, 3 April 2012 (UTC)

"In other laboratory studies Quercetin has been proven to mirror the effect of estradiol in the estrogen receptor beta (ERβ) which induces apoptosis in both normal and cancer cells along with reducing the speed of cell cycle and increasing apoptosis in a numerous different kind of cells including prostate, lungs, and breasts as well as the colon.

It mimics the cell cycle distribution of estradiol It works by inhibiting both enzymes and kinases along with breakage of DNA strands. In nutritionally relevant concentrations quercetin was proven to reduce cell populations by 25% in cancer infected HeLa cells. This was completed with the use of p38 Kinase of which Quercetin has the ability to directly activate along with caspase-3 activation, this has been tested by the use of HeLa cells that have been pre-treated with p38 Kinase and or caspase-3 inhibitors. Quercetin was able to induce p38 phosphorylation in the same amount of time as the estradiol. Even at very low levels quercetin was proven to activate pro-apoptosic cascade, which resulted in smaller cell numbers. This could be used to treat colon cancer in males, which it is more prevalent then in women due to it being mostly prevented from a female steroid hormone signaling. Along with all of the cancer inhibiting properties it is also been proven to be a form of anti-oxidant and can be found in several vegetables and fruits."


 * Excuse me Zefr but this article has been sited by two other sources at the time i read it which means it is no longer primary but secondary and has been used as a reference for following research. Shouldn't that mean it can be posted on the actual site instead of the talk site?? Duche831 (talk) 13:58, 6 April 2012 (UTC)
 * In the field of science, a secondary source is a review of primary sources. If a primary source is cited by another source, the first source is still a primary source.  I think in this context of these citations, WP:MEDRS is too restrictive and WP:SCIRS should apply.  One thing for sure however is that speculations as to the relevance in humans should be removed.  Boghog (talk) 15:47, 6 April 2012 (UTC)

There is an article at that says that Quercetin is a drug that slows the aging process. This seems important but I don't know how to responsibly edit the Quercetin article to add this new reference. Can someone help? 69.196.188.247 (talk) 00:17, 13 March 2015 (UTC)


 * As this news release reports the use of quercetin in cell culture and in mice, the work is preliminary and WP:PRIMARY applies. No conclusion about interruption of the aging process in humans can be made from this research. Accordingly, it should not be included in the article. --Zefr (talk) 01:19, 13 March 2015 (UTC)

Table cannot be sorted
Table cannot be sorted properly (ascending / descending buttons do not work properly).

62.195.45.181 (talk) 13:01, 18 January 2014 (UTC)

Recent edit
An IP editor keeps adding information cited to this this ref to the article. As an in vitro study, this would appear to violated WP:MEDRS and WP:WEIGHT. Further comments welcome. Yobol (talk) 22:57, 20 August 2014 (UTC)

food, enzyme
The table lists many foods containing significant amounts of quercetin. However, under "Effects of consumption..." it states: Quercetin itself (aglycone quercetin), as opposed to quercetin glycosides, is not a normal dietary component. This appears inconsistent. Also, under Biosynthesis 7,2'-dihydroxy-4'-methoxyisoflavanol synthase seems to be the wrong enzyme. 69.72.92.28 (talk) 23:27, 31 August 2014 (UTC)

Complaint about this article at WP:ANI
Please see WP:ANI, opened by. Zefr says that content is being added that does not conform to WP:SCIRS or WP:MEDRS. Three editors named in the complaint are, and. Anyone interested can respond to that complaint. EdJohnston (talk) 01:13, 5 December 2014 (UTC)
 * Fully protected for a week. At least two of these editors are copy and pasting from sources. and  Doc James  (talk · contribs · email) 01:46, 5 December 2014 (UTC)

The yellow in pickled onions
I have seen it referenced that Quercetin crystallising out is the cause of yellow spot in pickled onions, e.g here:. Would be good to add this somehow Fig (talk) 14:20, 23 February 2015 (UTC)

Recent research
A reference I picked up from http://www.kurzweilai.net/drugs-that-dramatically-increase-healthy-lifespan-discovered-by-scripps-research-mayo-clinic.

http://dx.doi.org/10.1111/acel.12344 "[...]Dasatinib eliminated senescent human fat cell progenitors, while quercetin was more effective against senescent human endothelial cells and mouse BM-MSCs. The combination of dasatinib and quercetin was effective in eliminating senescent MEFs. In vivo, this combination reduced senescent cell burden in chronologically aged, radiation-exposed, and progeroid Ercc1-/Δ mice. In old mice, cardiac function and carotid vascular reactivity were improved 5 days after a single dose.[...]" 585ad205105278a06716f2ebe4c82c92 (talk) 14:48, 11 March 2015 (UTC)
 * We need WP:MEDRS to support biomedical information; this isn't. Alexbrn talk 14:54, 11 March 2015 (UTC)

Medical effects
This substance is listed on the article about mast cell stabilising therapies as being a known treatment.

The heated debate about effects re cancer and health effects in general is so long, I can't digest all of it right now, but didn't see a reference to treatment for mast cell disorders. Tufts researchers (Dr Theoharides and others) have published research about certain trials of the use of this and other flavonoids to treat mast cell activation disease/syndrome (and I think for autism too). The article presently reads as though it is rightly correcting popular misconceptions/myths/speculation about medical effects by being very dismissive of claimed health benefits in the treatment of cancer. However it is not true to say that there is no evidence for any health effects for quercetin and the fact that it is being actively investigated for MCAS and other conditions is worthy of mention.

The debate about this is very lengthy and clearly there is dispute and controversy, so I don't feel comfortable making edits myself as I'm not able to seek out the relevant research papers myself and suspect I'll incur the wrath of someone or other if I try to edit without referencing!!

As I general note, I don't think it is appropriate to be too assertive about something that is being actively researched either way. Just because the evidence may be relatively new or under way does not make it right to assert that no benefits exist. Simply acknowledging the facts, ie that studies are underway or that early studies have shown that there is a possible health effect should not be controversial. Of course, that doesn't mean overstating weak evidence is sensible. Stating facts is what Wikipedia should be about, not over-zealous censorship IMO. Zctyp18 (talk) 11:09, 26 November 2015 (UTC)
 * Ongoing research not yet adopted by collective scientific agreement in a published, peer-reviewed article and regulatory approval (if a new drug or therapeutic procedure) is considered preliminary and would have to be discussed as such. For addressing any human disease, this requires sources that meet WP:MEDRS, a document worth reading and consulting for any edits. Also, please use the icon to time stamp and sign the end of your comments (I moved your signature to the end of your statement). --Zefr (talk) 16:40, 26 November 2015 (UTC)

GPER agonist activity and MEDRS
The statement that quercetin is an GPER agonist was deleted in this edit with the justification lab research only; not proved as relevant to humans; and WP:PRIMARY with the implication that the supplied source is not WP:MEDRS compliant. The material was added to a reasearch and not a clinical significance section and no medical/therapeutic claims are being made hence it is outside of the scope of MEDRS but within the scope of WP:SCIRS. In addition the source is a review article that in turn cites. In later source, it is stated that quercetin was found to be an agonist of GPER in the human cancer cell lines MCF7, MDA-MB-231, BT-20, and SKBR3. Hence I have restored the material but made clear that the results were obtained in human cell cancer lines. Boghog (talk) 18:33, 1 January 2016 (UTC)
 * Thanks for the explanation, Boghog. Although I understand your reasoning, I find the rationale that this information is relevant to a general-user encyclopedia to be distorted, more so for this article on Quercetin than acceptable for many similar articles or those presenting lab research as relevant to MEDRS topics. My issue is that even human cell lines are years/decades from being proved relevant to human physiology or therapy. To me, much of the article on "Metabolism" is non-compliant with WP:NOTJOURNAL and should more closely follow the discussion under "Health effects". We seem to be giving this topic a pass on whether it is readable or relevant to a lay user's understanding of a compound still in the early stages of research. In the same Research section where the GPER receptor is discussed could be dozens of other lab/in vitro findings far from being proved relevant to humans, so also fall under WP:NOTJOURNAL. Same applies to Resveratrol, Oleuropein, Hydroxytyrosol and others edited today with this same information by Medgirl131. --Zefr (talk) 19:34, 1 January 2016 (UTC)
 * Thanks for your reply Zefr. I think we need to find a middle ground. I agree that we must be very careful not to make any medical claims and the artiticle already clearly states that there is no evidence that quercetin has any therapeutic benefit. On the other hand, Wikipedia's audience conforms to the long tail and the scope of Wikipedia is larger than WP:MED, it also includes WP:MCB. Quercetin is being used as a research tool as documented in reliable secondary sources hence I think mention of its in vitro pharmacology is appropriate.  In this context, whether quercetin ever becomes a drug is irrelevant. Quercetin also is being consumed by humans, so mention of its pharmokinetics and metabolism is also relevant. Boghog (talk) 23:52, 1 January 2016 (UTC)
 * Concerning GPER, clearly demonstrates that GPER does have human relevance. I disagree that Wikipedia articles should be restricted only to content that can be understood by lay readers. There is a hierarchy of articles from the most general where it is essential that it be understood by a wide audience to the more specialized that may only be of interest to a small but important fraction of readers. Furthermore, it is dangerous to make assumptions about what others may be interested in reading. Most of what we currently know about GPER comes from in vitro and animal studies.  GPER, its endogenous ligand estradiol, and the signal transduction pathway through which GPER works is highly conserved in vertebrates including humans.  The specialist reader will understand that what we learn from animals may not necessarily translate into humans and not all research can be repeated. I do agree that we should preferentially use secondary sources which in the case of GPER are now starting to appear (e.g., ). Boghog (talk) 10:32, 2 January 2016 (UTC)
 * Not a debate with a simple "middle ground" to resolve, Boghog. Your comments today lead to a slippery slope, in my opinion, because the abundance of in vitro work (even if secondary), is still vague for physiological relevance and opens Pandora's box for similar content being added to the Quercetin article and dozens like it. In the example of the long tail, the sweet spot should be on the left side of the green majority because, to the right in yellow where in vitro discussions lie, the meaning of a general consumer encyclopedia changes to text book (WP:NOTTEXTBOOK). Viewing your user contributions, I want to respect your point of view as a biochemist or like professional. However, taking a page from the process of drug discovery, the standards for which interpreting cause and effect in human physiology apply to receptor mechanisms and in vivo roles of compounds like quercetin (giving it WP:UNDUE weight in the article at present), there will be the same conversation going on in 2026. Meanwhile, the interested lay user has to wade through the lab gobbledygook as exists under the Pharmacology section. In interest of satisfying the in vitro scientists and literate lay user groups, I say both types of encyclopedia users are important to write for, but WP:NFRINGE, WP:MEDANIMAL and the hierarchy of evidence under WP:MEDASSESS should prevail for more general statements about in vitro work until proven applicable in vivo.
 * With effort, the sections under "Metabolism" and "In vitro pharmacology" could be trimmed or written more generally with digestible prose for literate lay users (or even physiologists, like myself). Reminders under WP:NOTJOURNAL, numbers 6-8: (6) "Wikipedia is an encyclopedic reference, not a textbook. The purpose of Wikipedia is to present facts, not to teach subject matter. It is not appropriate to create or edit articles that read as textbooks"; (7) "A Wikipedia article should not be presented on the assumption that the reader is well versed in the topic's field. Introductory language in the lead (and also maybe the initial sections) of the article should be written in plain terms and concepts that can be understood by any literate reader of Wikipedia without any knowledge in the given field..."; (8) "Texts should be written for everyday readers, not just for academics." --Zefr (talk) 17:15, 2 January 2016 (UTC)
 * I think the addition is ok here. But it is perhaps as well that it has been left incomprehensible to the vast majority of readers, though this is against policy (as explained above). GPER, by the same team, is also a masterpiece of obscurity, apart from the last sentence. Johnbod (talk) 18:38, 2 January 2016 (UTC)
 * How can the addition be both OK and against policy? This makes no sense.  What Wikipedia policy in WP:NOTJOURNAL says is Introductory language in the lead (and also maybe the initial sections) of the article should be written in plain terms and concepts. Of course, we should strive to make the presentation as clear as possible, especially the lead sentence, but there is nothing in Wikipedia policy that prohibits the presentation of complex topics. Not every section in every Wikipedia article will be of interest to a wide audience. Boghog (talk) 19:32, 2 January 2016 (UTC)
 * The passage makes absolutely no attempt to make itself more widely comprehensible, which could very easily be done. It is not exactly "complex" in itself, compared to many scientific matters. GPER is the same right from the get-go, so excuse me if I don't give your views on correct Wikipedia style in science articles much weight. Johnbod (talk) 02:11, 3 January 2016 (UTC)
 * You have misinterpreted both what I have written and Wikipedia policy. What part of we should strive to make the presentation as clear as possible don't you understand? Regardless, I have rewritten the lead in GPER so that is now dead simple. Boghog (talk) 06:53, 3 January 2016 (UTC)
 * I have also rewritten the in vitro pharmacology section so that it is hopefully now more accessible. Boghog (talk) 08:12, 3 January 2016 (UTC)


 * I agree w/ Boghog, more complex material/text can and should be added after the lead--Ozzie10aaaa (talk) 20:01, 2 January 2016 (UTC)
 * Complexity is not the issue, Ozzie10aaaa. An encyclopedia of > 5 million articles covers tens of thousands of complex topics, but hopefully with the goal of making them comprehensible for the literate lay user. Respectfully, the dense jargon Boghog inserted today under In vitro pharmacology ignores logic and service to lay users per MOS:JARGON, WP:PRIMARY and WP:MEDANIMAL. The content for quercetin entered under "Pharmacology" should be held to WP:MEDRS rigor because it is part of the continuum for defining the human condition. Such antioxidant functions as described, for example, are an in vitro observation only, not known to exist in vivo, so mislead a lay reader into believing quercetin has importance as a dietary antioxidant. In dozens of topics similar to Quercetin that I've followed over the 15 years of Wikipedia's life, similar content has been reversed by other editors and myself as too preliminary and scientifically esoteric to mention, falling under WP:UNDUE. Scientist editors know in vitro or animal research is factually tentative for the human condition, almost certain to be changed or proved irrelevant when tested in humans in future years. Such a section serves a small percentage of encyclopedia users, has significant likelihood to exaggerate importance or mislead, and defeats the intent of WP:! and WP:NOTJOURNAL. --Zefr (talk) 18:02, 3 January 2016 (UTC)
 * Zefr: I respectfully disagree with just about everything you have written above. The scope of Wikipedia is considerably larger than the human condition. Furthermore the scope of  WP:MED has limits.  No medical claims are being so WP:MEDRS clearly does not apply. And the material that I have added is dense?  What exactly is difficult to understand?  I strongly suspect the problem here is not lack of understanding, but lack of interest.  While this material may not be interest to you, it may be of interest to others.  Boghog (talk) 18:49, 3 January 2016 (UTC)
 * Boghog: this discussion is at an impasse. Our editing contributions serve different audiences, yours favoring scientific specialists at the far right of the long tail, whereas mine aspire to make scientific topics comprehensible generally for non-scientists, as summarized a few paragraphs above with italicized excerpts from WP:NOTJOURNAL. One comment concerning MEDRS: all the article's sections are "biomedical" content and human-related, holding Quercetin to WP:MEDRS standards. The "Metabolism" and "In vitro pharmacology" sections are lab or preliminary observations only, described in jargon unintelligible to the lay user and not proven to exist in humans in vivo. These two sections and their sources do not comply with WP:MEDANIMAL and WP:PRIMARY. Thanks for the friendly debate. --Zefr (talk) 18:19, 4 January 2016 (UTC)
 * Zefr: A couple of final thoughts. The occurrence and biosynthesis sections are not biomedical related. They concern how bacteria and plants synthesize, modify, and degrade quercetin. In the pharmacology section, 5 of the 7 sources are secondary. The source supplied for the metabolism section  reviews human data. What I have included is compliant with WP:MEDANIMAL because this material is based on secondary sources (or in one case, two independent primary sources ), is not reliant on a single study, and does not make any medical claims. Also the question I raised above still has not been answered: What exactly is difficult to understand?  Even if what I wrote is unintelligible jargon (and I dispute this), it is not inherently so and can be improved if necessary through copyedit. Finally, and most importantly, the intention of WP:NOTJOURNAL is to make Wikipedia useful for all audiences including specialists. This is not an either/or proposition.  Both audiences can be served by making the lead accessible.  Insisting that the entire article be written this way is not always realistic nor is it required by WP:NOTJOURNAL. Cheers. Boghog (talk) 06:15, 5 January 2016 (UTC)

Boghog: 1) Although unable to read the whole Russo article to tell if the content represents anything more than in vitro research, I find its title, "... against cancer", the second half of the abstract and Russo's other publications on quercetin are delirious, over-the-top exaggerations about quercetin having a preventive effect on cancer or other disease mechanisms; 2) the in vitro sources you cite to support quercetin activity on the estrogen receptor are overstated for the level of scientific proof established. They are not factual for the in vivo human condition, but rather are artificially-developed, preliminary findings (granted, they are important for scientific development) questionable per WP:MEDANIMAL - "in vitro and animal-model findings do not translate consistently into clinical effects in human beings" and ... "the article text should avoid stating or implying that reported findings hold true in humans"; 3) What exactly is difficult to understand?: the second sentence under "Metabolism" and all of the "In vitro pharmacology" section are both non-factual and gibberish to a non-scientist encyclopedia user. WP:NOTJOURNAL, #6-8: ... present facts, not teach subject matter; write for everyday readers, not just for academics. Proposed edits: 1) the Metabolism section subtitle is misplaced, as it is not "Pharmacology"; 2) the second sentence under Metabolism should be removed, as the content is fringe and weakly referenced; 3) the In vitro pharmacology" section should be removed as jargonistic, non-factual and presently irrelevant to the in vivo condition per WP:MEDANIMAL. --Zefr (talk) 17:37, 7 January 2016 (UTC)
 * Zefr: There are a whole lot of misconception above that need to be corrected:
 * delirious, over-the-top exaggerations I don't know much about this author, but his CV doesn't suggest to me that he is delirious. The linked title in the citation provides the full text.  It is clear from the source that the authors have reviewed the human quercetin metabolism data. Just to remove any doubt, I have added an additional secondary source by different authors documenting the human metabolism of quercetin:
 * in vitro sources you cite to support quercetin activity on the estrogen receptor are overstated The sources fully support the statement that quercetin binds to the estrogen in vitro. I can supply dozens more sources to further support the statement (e.g., ).  But this would be overkill.
 * not factual for the in vivo human condition The scope of Wikipedia is wider than the human condition.
 * "Metabolism" and all of the "In vitro pharmacology" section are both non-factual and gibberish Both sections are completely factual and are supported by the sources supplied.  Stating that the sections are gibberish is your opinion and not fact.  Could they be made clearer?  Probably, but I strongly dispute that they are gibberish.
 * the Metabolism section subtitle is misplaced, as it is not "Pharmacology" It is properly placed according to WP:PHARMOS. The discipline of metabolism is part of pharmacokinetics (what the body does to the drug) which in turn a subdiscipline of pharmacology.
 * the second sentence under Metabolism should be removed, as the content is fringe and weakly referenced The sentence is supported by a reliable secondary source and therefore by definition is not fringe.
 * In vitro pharmacology" section should be removed as jargonistic, non-factual and presently irrelevant to the in vivo condition Irrelevant that it is irrelevant to the in vivo condition because the section heading states "In vitro". Boghog (talk) 19:07, 7 January 2016 (UTC)
 * You still have not answered my question What exactly is difficult to understand?. Your opinion  the second sentence under "Metabolism" and all of the "In vitro pharmacology" section are both non-factual and gibberish to a non-scientist encyclopedia user is not an answer. Please answer the question. Boghog (talk) 20:45, 7 January 2016 (UTC)  One last comment.  You keep repeating the phrase "non-factual" with the implication that if hasn't been demonstrated in humans, it is isn't important or worse, it isn't true.  This anthropocentric view point is not supported by Wikipedia policy. Boghog (talk) 22:36, 7 January 2016 (UTC)
 * You still have not answered my question What exactly is difficult to understand?. Your opinion  the second sentence under "Metabolism" and all of the "In vitro pharmacology" section are both non-factual and gibberish to a non-scientist encyclopedia user is not an answer. Please answer the question. Boghog (talk) 20:45, 7 January 2016 (UTC)  One last comment.  You keep repeating the phrase "non-factual" with the implication that if hasn't been demonstrated in humans, it is isn't important or worse, it isn't true.  This anthropocentric view point is not supported by Wikipedia policy. Boghog (talk) 22:36, 7 January 2016 (UTC)

My two cents:
 * Wikipedia is intended for all audiences, not just the lay reader. This means that it can and should include some information that is only "interesting" to professional chemists, biologists, drug developers, engineers, investors, etc.
 * It is ideal for Wikipedia's contents to be understandable by a motivated, educated non-specialist. However, an apparent need for simplification or copyediting is not a justification for removing accurate information.
 * If a reader really believes that taking dietary antioxidant supplements will improve his health, then the reader has problems well beyond the scope of this article. At any rate, we don't (per guideline) write articles in a way that suppresses accurate information for the purpose of helping readers make the "right" real-world choices about their health.  WhatamIdoing (talk) 18:36, 4 January 2016 (UTC)
 * I'm sort of late to the discussion, but I'll just state it outright: if a statement of fact is directly supported by a fully MEDRS-compliant source on wikipedia, there's virtually no grounds to actually remove a statement from a biomedical article on wikipedia; it may be appropriate to rephrase it so as to put the coverage of the fact in an appropriate context in the article (e.g., if the statement is contested by another MEDRS-quality source or if the statement in the article isn't entirely accurate w.r.t. the cited reference), but removing text which is cited and directly supported by fully MEDRS-compliant source is nearly always a red flag to me. The only exception that comes to mind is circumstances in which a review makes a statement which is clearly not supported by the evidence which it cited (assuming it cited any), which would be a failure of journal peer-review.  Seppi  333  (Insert 2¢) 11:19, 12 January 2016 (UTC)

External links modified
Hello fellow Wikipedians,

I have just modified 1 one external link on Quercetin. Please take a moment to review my edit. If you have any questions, or need the bot to ignore the links, or the page altogether, please visit this simple FaQ for additional information. I made the following changes:
 * Added archive https://web.archive.org/web/20110916172444/http://www.pvp.com.br:80/EN_quercetin_dihydrate_safety_data.htm to http://www.pvp.com.br/EN_quercetin_dihydrate_safety_data.htm

When you have finished reviewing my changes, please set the checked parameter below to true or failed to let others know (documentation at ).

Cheers.— InternetArchiveBot  (Report bug) 21:32, 12 November 2016 (UTC)

Health claims, antioxidant properties
Regarding the statement that the two letters from the FDA emphasize that quercetin is not an antioxidant, from a quick review of the letters I could find no evidence of this. The previous section of this article states that it is classified as antioxidant and one of the other sources referenced [30] takes for granted that it has antioxidant properties regardless of health claims.Kileytoo (talk) 15:17, 10 May 2018 (UTC)
 * Quercetin has antioxidant properties only in a test tube; there is no high-quality evidence it has any biological roles in vivo, as discussed in the article. From the FDA warning letter to River Hills Harvest: "The nutrient content claim for your "100% Pure Premium ElderBerry Juice" product of "a great source of antioxidant flavonoids quercetin and rutin as well as seven different anthocyanins the same four present in the European S. nigra plus three more" does not meet the requirements to make such a claim because there are no established RDIs for quercetin, rutin or any anthocyanins. Therefore, the claim "a great source of antioxidant flavonoids quercetin and rutin as well as seven different anthocyanins the same four present in the European S. nigra plus three more" does not meet the requirements of 21 CFR 101.54(g) and misbrands your product under section 403(r)(1)(A) of the Act." --Zefr (talk) 22:24, 10 May 2018 (UTC)

Reference 26 (Graefe et al.,) query
There is a sentence in the "Pharmacokinetics" section,

"The oral bioavailability of quercetin in humans is low and highly variable (0-50%) and is rapidly cleared (elimination half-life of 1–2 hours after IV injection).[26]"

After checking the reference, surely it should be "1-2 hours after oral administration" instead of "1-2 hours after IV injection"? Otherwise an additional reference should be cited for IV clearance time.158.194.9.187 (talk) 12:14, 18 April 2017 (UTC)

DARPA report
I readded a statement that The US military research agency DARPA reported in May 2009 that it had developed a new form of Quercetin that is now available to the military and the general public., which was reverted by with the comment "Weight?". My understanding of WP:UNDUE is that neutrality requires that mainspace articles and pages fairly represent all significant viewpoints that have been published by reliable sources, in proportion to the prominence of each viewpoint in the published, reliable sources. If I state that the military did something, and that statement is backed by a published statement by the military itself, to remove this content would be removing the mainstream viewpoint, possibly in support of some conspiratorial view that the military is lying about ever doing that thing. But that's not what's happening here. To state the fact that the military researched and used Quercetin isn't a historically convenient fact to those attempting to push a certain point of view. Does Wikipedia endorse suppressing historical fact for medical reasons? Are we going to now delete facts about how the US government used Bloodletting on George Washington? MarshallKe (talk) 16:25, 27 October 2021 (UTC)

Not only is that DARPA source 12 years out of date, there is no source in the report or the general medical literature to support the extraordinary health claim, WP:EXTRAORDINARY. As the content and source added by MarshallKe were in the health claims section, and there is no reputable source to support such a claim (certainly not the US DoD), the edit has no WP:WEIGHT. Zefr (talk) 16:44, 27 October 2021 (UTC)
 * Agreed: DARPA said DARPA did something twelve years ago. Not due to mention, and especially not to imply via Wikivoice that it's relevant today wrt health. Alexbrn (talk) 16:56, 27 October 2021 (UTC)
 * Thanks. If I had kept it out of the health claims section and instead in a section name that did not imply relevance to health, would you have accepted the edit? If not, would it have mattered if I had found a reliable news source that stated the same? MarshallKe (talk) 17:29, 27 October 2021 (UTC)