March 28 2014

Quercetin is a plant pigment in many foods — onions, apples, berries, tea, and red wine. It's not a nutrient, but is classified as a flavonoid. Once thought to be vitamins, flavonoids were given such names as vitamin P and vitamin C2. Like many other plant chemicals, it is sold as a dietary supplement. 

buy Activated Quercetin and Bromelain
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Activated Quercetin with bromelain is a unique bioflavonoid derived product from plant sources. In human cell culture studies, Quercetin has been shown to inhibit histamine release. Additional research needs to be conducted to confirm the benefits, if any, in humans. Bromelain is a pineapple enzyme. Magnesium ascorbate is a buffered (non-acidic) form of vitamin C that helps support the immune system.

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Benefit
Quercetin is a flavonoid found in onions and other vegetables. It is known that dietary quercetin is metabolized in the intestinal mucosa and the liver and is present as its glucuronide / sulfate conjugates with or without methylation.

Cancer
Quercetin has anti-tumor potential. In humans, the total average intake of quercetin and kaempferol is estimated at 20 mg a day and consumption of the former from onions and apples reduces lung cancer risk.

Quercetin inhibit human SW480 colon cancer growth in association with inhibition of cyclin D1 and survivin expression through Wnt/beta-catenin signaling pathway.
Cancer Invest. 2009.
The Wnt signaling pathway plays a pivotal role in cellular developmental processes and human carcinogenesis. The aim of this study was to investigate the effects of quercetin on the growth of the colon carcinoma cell line and the regulation effect on the Wnt/beta-catenin signaling pathway. Our results indicate that the molecular mechanism underlying the antitumor effect of quercetin in SW480 colon cancer cells is related to the inhibition of expression of cyclin D(1) and survivin as well as the Wnt/beta-catenin signaling pathway. Therefore, the Wnt/beta-catenin signaling pathway could be qualified as one of the promising targets for innovative treatment strategies of colorectal cancer.

Heart disease
Quercetin inhibits the proliferation and migration of aortic smooth muscle cells, concomitant with inhibition of mitogen-activated protein kinase phosphorylation. These findings provide new insights and a rationale for the potential use of quercetin in the prophylaxis of cardiovascular diseases.

Polyposis
Combination treatment with curcumin and quercetin of adenomas in familial adenomatous polyposis.
Clin Gastroenterol Hepatol. 2006.
Familialadenomatous polyposis is an autosomal-dominant disorder characterized by the development of hundreds of colorectal adenomas and eventual colorectal cancer. Regression of adenomas in this syndrome occurs with the administration of nonsteroidal anti-inflammatory drugs and cyclooxygenase-2 inhibitors, but these compounds can have considerable side effects. We evaluated the efficacy of the combination of diet-derived nonprescription supplements curcumin and quercetin to regress adenomas. Five familialadenomatous polyposis patients with prior colectomy (4 with retained rectum and 1 with an ileal anal pouch) received curcumin 480 mg and quercetin 20 mg orally 3 times a day. All 5 patients had a decreased polyp number and size from baseline after a mean of 6 months of treatment with curcumin and quercetin.
   Comments: The quercetin dosage was very small, and we are not sure if it had much of an effect.

Prostate gland
Quercetin my inhibit the proliferation of androgen-independent human prostatic tumor cells. Saw palmetto extract for prostate gland. For more prostate saw palmetto information and research.

Prostatitis
My doctor recommended me to take 500mg of quercetin pills two times a day for prostatitis (one in the morning and one at night). I have found it has considerably helped me aliviate my symptoms. I have come across several theories that quercetin pills might cause birth defects in the offspring of people who are taking it regularly. I am male, and I am 30 years old. My wife and I will try to have children pretty soon and I am worried about this risk. Is there accurate proof to show that my children could potentially have birth defects because of using it? If there is uncertainty about this risk, I could stop taking it prior to conception, and then re-taking it afterwards. How much time do you think I need to let pass by for my body to 'de-tox' from it prior to trying to have children? I really appreciate your help as there does not seem to be much out there on the subject. I am pleased to find your webpage which is very helpful.
   We are not aware of any human studies that indicate quercetin supplements taken by a male cause harm to the fetus. The effects of most supplements usually go away within a few days of stopping. We wish you a healthy and happy baby.

Use by children
Q. I would like to know if a quercetin supplement is safe for children of 2 – 3 years old, that suffers from allergic rhinitis? Also what would be the recommended dose per day?
   A. We have not seen research with its use in children and do not know about safety or proper dosage.

Aromatase inhibitor
I was looking at purchasing quercetin supplement. I’ve read that it is one of the best flavones and aromatase inhibitors, however you don’t mention that it’s an aromatase inhibitor on your webpage. Is quercetin also an aromatase inhibitor? Which supplements can also be considered aromatase inhibitors?
   Plants have substances such as flavonoids that influence or inhibit the aromatase enzyme. There are countless substances in plants that inhibit aromatase, not just quercetin. Some of these include chrysin, naringenin, apigenin, and genistein. Not enough research is available to determine which of the flavonoids or other substances found in plants is the most effective aromatase inhibitor. As a general rule, it is preferable to ingest a variety of flavonoids rather than focusing on only one or two. 

Quercetin and prescription drug interaction potential
Short-term effect of quercetin on the pharmacokinetics of fexofenadine, a substrate of P-glycoprotein, in healthy volunteers.
Eur J Clin Pharmacol. 2009
The aim of the present study was to assess whether quercetin exhibited any inhibitory effect on P-glycoprotein (P-gp)-mediated drug disposition in humans using fexofenadine as a P-gp substrate.Twelve healthy subjects were enrolled in the study and treated daily for 7 days with 500 mg quercetin or placebo 3 times a day. On day 7, a single dose of 60 mg fexofenadine was administered orally. The results of the present study show that short-term use of quercetin elevates the plasma concentrations of fexofenadine, probably by the inhibition of P-gp-mediated efflux in humans.

The simultaneous effects of flavonoid quercetin on the activities of CYP1A2, CYP2A6, NAT2 and XO in healthy volunteers.
Clin Exp Pharmacol Physiol. 2009.
Quercetin, one of the most abundant natural flavonoids, has been reported to modulate activities of several drug metabolizing enzymes. The present study was designed to investigate the effect of quercetin on CYP1A2, CYP2A6, NAT2 and XO activity in healthy volunteers, using caffeine as probe drug. 2. 12 unrelated healthy volunteers were recruited for the study. 500mg quercetin capsules were given to each volunteer once daily for 13 continuous days. The results showed that quercetin inhibited function of CYP1A2, while enhanced the activities of CYP2A6, NAT2, and XO. Simultaneously, some pharmacokinetic parameters of 17X were also affected by quercetin. We thus concluded that quercetin affected the activities of CYP1A2, CYP2A6, NAT2 and XO in vivo.

Quercetin level and cooking
Influence of domestic processing and storage on flavonol contents in berries.
J Agric Food Chem. 2000.
Effects of domestic processing and storage on the flavonols quercetin, myricetin, and kaempferol in five berries were studied using an optimized RP-HPLC method with UV and diode array detection after an acid hydrolysis of the corresponding glycosides. In fresh berries, the total content of flavonols was highest in lingonberry (169 mg/kg) and black currant (157 mg/kg), intermediate in bilberry (41 mg/kg) and strawberry (17 mg/kg), and lowest in red raspberry (9.5 mg/kg). Cooking strawberries with sugar to make jam resulted in minor losses (quercetin 15%, kaempferol 18%). During cooking of bilberries with water and sugar to make soup, 40% of quercetin was lost. Traditional preservation of crushed lingonberries in their own juice caused a considerable (40%) loss of quercetin. Only 15% of quercetin and 30% of myricetin present in unprocessed berries were retained in juices made by common domestic methods (steam-extracted black currant juice, unpasteurized lingonberry juice). Cold-pressing was superior to steam-extraction in extracting flavonols from black currants. During 9 months of storage at 20 C, quercetin content decreased markedly (40%) in bilberries and lingonberries, but not in black currants or red raspberries. Myricetin and kaempferol were more susceptible to losses during storage.

Quercetin dihydrate information
Quercetin dihydrate is a flavonoid compound hydrolyzed and crystallized from rutin.  One source is extracted from the un-bloomed bud of Sophora japonica.

Quercetin dihydrate and gallate supplements lower plasma and hepatic lipids and change activities of hepatic antioxidant enzymes in high cholesterol-fed rats.
Int J Vitam Nutr Res. 2002.
This study was designed to test the lipid-lowering and antioxidant activity of two bioflavonoids, quercetin dihydrate and gallate. Results suggest that the supplementation of quercetin dihydrate and gallate promotes an increase in fecal sterols, which in turn leads to a decreased absorption of dietary cholesterol as well as lower plasma and hepatic cholesterol.

Research study
Consumption of black currants, lingonberries and bilberries increases serum quercetin concentrations.
Eur J Clin Nutr. 2003.
To study serum quercetin concentrations of subjects consuming berries or habitual Finnish diets. Randomized parallel dietary intervention. Forty healthy men (age 60 y). Twenty subjects consumed 100 g/day of berries (black currants, lingonberries and bilberries) for 8 weeks. Twenty subjects consuming their habitual diets served as controls. Fasting blood samples were obtained 2 weeks prior to the study, at baseline, and at 2, 4 and 8 weeks. Intake of quercetin was assessed from 3 day food records collected at baseline and at 8 weeks. The serum quercetin concentrations were significantly higher in the subjects consuming berries compared to the control group. During the berry consumption period the mean serum concentrations of quercetin ranged between 21.4 and 25.3 micro g/l in the berry group, which was 32-51% higher compared with the control group. According to 3 day food records, there was no difference in quercetin intake at baseline, but at 8 weeks the intake was 12 mg/day in the berry group and 5.8 mg/day in the control group. The results indicate that the berries used in this study are a good source of bioavailable quercetin.

Emails
Q. I believe that Quercetin works together with Vitamin C and E. I believe one needs to combine it with these chemicals. They actually work in concert in scavenging free radicles and charging the pro-apoptotic effect of quercetin. Alone it may lack effect it's cancer killing effect. If you look at the molecular structure of vitamin C and E you will notice there is something in common. I believe they work together in scavenging free radicles, that charge the ability of quercetin to induce apoptosis.
   A. Thank you for your email. We prefer seeing actual studies regarding these combinations.

Q. I hope this isn't too personal but in the interest of Science I thought I might share. I have been taking Solaray QBC Complex for about 3-4 months now. For the first 1 month, I was taking 2 capsules (500 mg) a day. Encouraged by the results, I up the dosage to 3 capsules (750 mg) twice daily with meals. Product: Solaray Non-Citrus QBC PLEX. 2 capsules of Solaray Non-Citrus QBC PLEX provide: Vitamin C 1250 mg, Quercetin 500 mg, Bromelain 50 mg. The reason I decided to take Solaray QBC PLEX was to determine what affects Quercetin might have on my chronic allergies. Well, I'm please to report the Quercetin compound has completely supressed my allergy symptoms. Unfortunately, this has not been without some side affects. The major side affect is a semi-reduced libido combined with lower sperm production. That aside, a more alarming side affect is that of yellow sperm. Fortunately, all symptoms subside as soon as I cease my dosage. So, I am wondering, what might be causing the yellow coloration? The Solaray QBC PLEX compound is a bright yellow. Is the side affect perhaps a result of the quercetin or Vitamin C source?
   A. This is very interesting. We don't have personal experience using high amounts of quercetin, but we do wonder if the yellow pigment of quercetin or its metabolites was incorporated within sperm fluid. Whether the bromelain placed a role in reducing libido or just the quercetin was involved is difficult to say. Perhaps you could try a product that has quercetin by itself and keep us updated. Quercetin research prostate quercetin for allergy.

Q. I came across an article that seemed to indicate that quercetin might be mutagenic, is this correct? Also, do you know of any studies, which have found quercetin to combat HPV and warts?
   A. We have not come across human studies that indicate its use causes changes in DNA or damages DNA. We also have not seen human studies that quercetin is helpful in treating HPV and warts. Quercetin is an interesting flavonoid supplement with potential clinical uses, but human research is lacking.

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