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The Blood Type Diet Archives Volume 10

More info on quercetin.

Posted By: Stephen
Date: Saturday, 26 June 1999, at 8:48 p.m.

In Response To: Why quercetin helps your hayfever (angela (O+), ENTP)

I love this bioflavonoid!!! According to Australia's TGA wisdom, it is banned here (please don't ask me why as there is no medical reason!!). Quercetin in wonderful for any inflammatory conditions (such as hay fever cause it inhibits 5-lipoxigenase (an enzyme that is a mediator of inflammation). You best A source is onions however, most fruits and vegies have some. Onions have the most bioavailable source. If you supplemement, take quercetin one hour before food (improved absorption), unless of course you have gut inflammation then its best taken with food because it will have a topical application on the gut. If you live in a country like Australia that has it banned, then rutin is the next best thing. When you absorb rutin and it crosses the gut wall, it loses a glucose molecule from its structure and ends up a "quercetin" molecule (please don't tell the Australian TGA this or they will ban that also!!!). Anyway, I have included a list below of some of its benefits.


Quercetin []

Also known as: Cyanidelonon 1522; C.I. Natural Yellow 10; C.I. Natural Red; Meletin; Quercetol; Quertine; Sophoretin; Xanthaurine


Quercetin is a type of Flavonol Bioflavonoid - note that Rutin is a Glycoside of Quercetin.

Health Benefits of Quercetin

Cardiovascular System

Quercetin helps to protect against Cardiovascular Diseases [scientific research].

Quercetin helps to prevent Stroke [epidemiological evidence].


Quercetin stabilizes Cell Membranes.

Digestive System

Quercetin is an effective preventative measure against Gastric Ulcers and is also a valuable treatment of existing Gastric Ulcers [scientific research – animals].


Quercetin helps to prevent Cataracts (by inhibiting the Aldose Reductase enzyme that catalyzes the conversion of Glucose to Sorbitol in the Lens of the Eye: the accumulation of Sorbitol in the Eye’s Lens results in Cataracts) [scientific research].

Immune System

Quercetin has demonstrated significant antitumor activity against various forms of Cancer including:

- Brain Cancer [scientific research - animals]
- Breast Cancer [scientific research - animals]
- Colon Cancer [scientific research - animals]
- Quercetin inhibits the synthesis of Deoxyribonucleic Acid (DNA) in Leukemia (including Promyelocytic Leukemia) cells (thereby preventing the replication of Leukemia cells) [scientific research - animals].
- Quercetin helps to prevent Lung Cancer [scientific research - humans: people who consume diets that include a high amount of Quercetin have a 46% reduction in their risk of Lung Cancer].

- Ovarian Cancer [scientific research - animals]
- Squamous Cell Carcinoma [scientific research - animals]
- Quercetin significantly inhibits the growth of Stomach Cancer [scientific research].

Quercetin prevents and alleviates the Common Cold (due to its ability to suppress Rhinoviruses) [scientific research - in vitro].

Quercetin suppresses many forms of Detrimental Fungi.

Quercetin reduces Inflammation:

- Quercetin inhibits the release of Acid Hydrolases from Lysosomes [scientific research -in vitro].
- Quercetin inhibits the production and release of Histamine by Basophils [scientific research].
- Quercetin stabilizes the Cell Membranes of Mast Cells, causing Mast Cells to become less reactive to the Antigens that are implicated in Allergies and decreases the ease with which they release their stored Histamine and Serotonin [scientific research - in vitro].

- Quercetin inhibits the production of inflammatory Series 4 Leukotrienes and Prostaglandin E2 within the body [scientific research - in vitro].

Quercetin prevents many infections caused by Viruses [scientific research - in vitro]:

- Quercetin helps to suppress the HIV virus (the Virus that causes Acquired Immune Deficiency Syndrome (AIDS) -
part of Quercetin’s ability to suppress the HIV virus stems from the inhibition of the Viral Reverse Transcriptase enzyme [scientific research].
- Quercetin suppresses the Herpes Simplex Type 1 Virus [scientific research - in vitro].
- Quercetin suppresses Picornaviruses [scientific research - in vitro].

- Quercetin suppresses Polio Viruses [scientific research - in vitro].
- Quercetin suppresses the Respiratory Syncytial Virus [scientific research - in vitro].
- Quercetin suppresses Rhinoviruses [scientific research - in vitro].
- Quercetin suppresses many strains of Influenza Viruses [scientific research - in vitro].


Quercetin is a potent Antioxidant [scientific research]:

- Quercetin inhibits Lipid Peroxidation [scientific research - in vitro].
- Quercetin deactivates Hydrogen Peroxide-induced Free Radicals and prevents Hydrogen Peroxide from damaging the DNA content of Cells [scientific research].

Quercetin lowers total serum Cholesterol levels [scientific research]:

- Quercetin inhibits the oxidation of LDL Cholesterol [scientific research - in vitro].

Quercetin helps to prevent many of the complications that arise from Diabetes Mellitus (by suppressing the Aldose Reductase enzyme) [scientific research].

Quercetin helps to prevent the further destruction of the Pancreas in persons afflicted with Pancreatitis (by suppressing the biosynthesis of Leukotriene B4 - a substance implicated in the Inflammation that occurs in Pancreatitis) [scientific research – humans].

Musculoskeletal System

Quercetin alleviates Otosclerosis (by inhibiting Otosclerosis-induced Bone remodeling changes in the Ear’s Bones) [scientific research].

Quercetin alleviates Rheumatoid Arthritis due to its anti-inflammatory properties [scientific research - animals].

Respiratory System

Quercetin alleviates Asthma.


Quercetin inhibits the Lipoxygenase pathway of Arachidonic Acid metabolism which is implicated in Psoriasis.

Quercetin Enhances the Function of These Substances


Quercetin is synergistic with Bromelain.

Quercetin Inhibits these Toxic Substances


Quercetin retards the production of 5-Lipoxygenase [this is desirable due to 5-Lipoxygenase stimulating the production of inflammatory Series 4 Leukotrienes].

Quercetin inhibits Aldose Reductase (the enzyme that catalyzes the excessive conversion of Glucose to Sorbitol which is implicated in many of the complications that arise in Diabetes Mellitus) [scientific research].

Quercetin inhibits Xanthine Oxidase [scientific research].


Quercetin inhibits the production of the inflammatory Prostaglandin E2 (PGE2).

Quercetin inhibits the production of the inflammatory Series 4 Leukotrienes.

- Quercetin inhibits the biosynthesis of Leukotriene B4 [scientific research].

These Substances Enhance the Function of Quercetin


Vitamin C protects Quercetin from Oxidation [scientific research].

Dietary Sources of Quercetin

Quercetin is normally present in dietary sources in its Glycoside form (e.g. Quercetin-3-o-Beta-d-Glucoside, Quercetin-3-l-Arabinoside, Quercetin-3-Arabinoside, Quercetin-3-Glucuronide; Quercetin-3-Rhamnogalactoside).

(mg of Quercetin per 100 mg)

Beverages: Red Wine
Fruit: Apples 25 Grapes

Herbs: Hawthorn Passion Flower
Vegetables: Broccoli Onions

Squash Kale


Dosage Recommendations

The therapeutic dosage of Quercetin is 1,000 - 3,000 mg (1 - 3 grams) per day:

- Many people who use supplemental Quercetin for the treatment of Allergies use a daily dosage of 1,400 mg.


Quercetin was formerly regarded as being poorly absorbed orally, however recent studies (undertaken during 1996) show that some orally-administered Quercetin is absorbed:

- Studies conducted during 1997 further elaborated on the bioavailability of Quercetin: the Quercetin in Onions is absorbed better than Quercetin in Apples (Apples’ Quercetin content is absorbed only 30% as efficiently as Onions’ Quercetin) [scientific research].

Commercial Availability of Quercetin

“Singular” Quercetin Supplements

Quercetin is available from health food stores and mail order supplement companies in the form of:

- 150 - 500 mg capsules

- 250 mg tablets

- liquid


Quercetin is an ingredient in many multi-Vitamin/Mineral formulas and most mixed Bioflavonoids formulas.

Quercetin is an ingredient in some formulas designed specifically for the treatment of Asthma/Hayfever.

Quercetin (in combination with Bromelain or other nutrients) is a component of many formulas designed specifically for the treatment of Allergies.

Quercetin is a component (up to 25 mg) of some specific purpose formulas (capsules) designed to improve Eyesight and Eye health.

Some Vitamin C products contain (up to 67 mg) added Quercetin.

Chemical Data

Chemical Names: 3,3',4',5,7-pentahydroxyflavone


Molecular Formula: C15H10O7

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