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Veterinarian Reviewed on June 10, 2012 by Paulina Nelega, RH
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Quercetin is a naturally occurring flavonoid of plant origin that actually gives many fruits and vegetables their red color. In its chemical form, it is a yellow crystalline compound.

History and Origin of Quercetin

Although only recently, such as within the last 40 years, stipulated as Quercetin, it was originally thought to be a vitamin and was given the name of C2 or Vitamin P.

Ancient Uses of Quercetin

Quercetin containing red onions were often ‘prescribed’ for a variety of ailments. Sometimes just within the room of an ill patient to absorb ‘vapors,’ but most often used in soup. Onion soup, especially red onion soup, was used to help relieve symptoms of Asthma. Quercetin may also be the reason behind the folk wisdom of ‘An apple a day keeps the doctor away.’

Modern Uses of Quercetin

Quercetin has anti-oxidant, anti-histamine, and anti-inflammatory properties. Quercetin may also be helpful in preventing certain types of harmful cancers, especially prostate cancer, and reduces the size of the prostate in non-cancerous situations. It also seems to help slow the growth of pancreatic cancer.

Anecdotal evidence suggests that Quercetin actually reduces the symptoms of both fatigue and depression. Research studies have also shown that Quercetin provides a reduction in blood pressure and an increase in a person’s overall cardiovascular health. In addition, Quercetin has been proven to actually increase a person’s aerobic endurance, whilst simultaneously reducing their susceptibility to a myriad of rhinoviral infections.

Quercetin inhibits the migration of smooth cell heart muscle and prevents any endothelial damage from occurring in a person’s heart. In large quantities, Quercetin is also thought to help reduce platelets from sticking together, thereby reducing the likelihood of blood clots and heart attack or stroke. It also helps reduce capillary fragility, a condition most commonly associated with the elderly that causes rupture and under the skin bleeding and bruising from minor contact impacts.

Animal studies have shown that liver and kidney damage was significantly reduced when Quercetin was pre-administered to rats given toxic amounts of paracetamol. Not only was actual cellular damage decreased, but return of normal cellular activity was re-established much more quickly. Quercetin may also counteract long term use side effects of haloperidol and other anti-psychotics on the brain, reducing the incidence or severity of catalepsy and bradykinesia- slowing down of body movements; or tardive dyskinesia- tremora and involuntary movements similar to Parkinson’s disease. It also reduces the cellular damage caused by Alzheimer’s type dementias in lab animal studies.

Because of its anti-histamine qualities it helps with seasonal Allergies and may also reduce some of the effects of asthma.

Side Effects of Quercetin

In a few cases, Quercetin has been known to cause headaches or upset stomach in people who are more sensitive. On the other hand, taking extremely high doses of Quercetin may eventually lead to excessive kidney damage. Before taking Quercetin alone as a dietary supplement, be sure to check with your primary care physician or naturopathic doctor first.

Food Sources of Quercetin

Black and Green Tea both contain Quercetin. Red fruits and vegetables, such as citrus fruit, broccoli, tomatoes, onions, chokecherries, lingonberries, cranberries, bog whortleberries, and raspberries, etc, also contain high amounts of Quercetin. In addition, Quercetin can also be found in red wines.

Read also: Chondroitin

Our Expert

Paulina Nelega, RH
Paulina Nelega, RH, has been in private practice as a Clinical Herbalist for over 15 years. She has developed and taught courses in herbal medicine, and her articles on health have appeared in numerous publications. She is very passionate about the healing power of nature. Ask Dr. Jan

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