Bioflavonoids such as Quercetin, Rutin, and Hesperidin are vital through their ability to increase the strength of the capillaries (blood vessels) and to regulate their permeability. They assist Vitamin C in keeping collagen, the intercellular “cement” in healthy condition; are essential for the proper absorption and use of vitamin C; prevent Vitamin C from being destroyed in the body by oxidation; are beneficial in hypertension; help hemorrhages and ruptures in the capillaries and connective tissues and build a protective barrier against infections.

Quercetin, a bioflavonoid obtained from buckwheat and citrus fruits, appears to stabilize the membranes of the mast cells that release histamine. Since quercetin’s action is preventive, it’s best taken daily a week or two before pollen season and continued throughout. Quercetin is used widely for sinus problems and aids in capillary fragility. Yellow onions contain high levels of quercetin, an especially potent antioxidant with some anti-inflammatory properties. It should be avoided during pregnancy.

No toxicity has been identified with quercetin. If taken in large doses, however, it can cause the blood pressure to decrease. Quercetin is available in powder and capsule form. The recommended dose is 200-400mg tid, best taken before meals.


Bioflavonoids can help with the following


Allergy / Intolerance to Foods (Hidden)

Some doctors use quercetin to block food allergies, though no published studies yet exist to support this. There is however good support for the use of Cromolyn sodium to block food allergic reactions. Cromolyn is made up of two molecules of quercetin.


Allergic Rhinitis / Hay Fever

Plants high in bioflavonoids such as quercetin and curcuma (rose hips, bilberry) are especially useful because they reduce your body’s production of histamines or leukotrienes (substances that cause allergy symptoms) and strengthen connective tissue.

Quercetin appears to stabilize the membranes of the mast cells that release histamine. Since quercetin’s action is preventive, it is best taken daily a week or two before pollen season and continued throughout.


Allergies Indoor

May reduce IgE formation, inhibit the release of histamine, and reduce or eliminate allergy symptoms.


Chronic Venous Insufficiency (CVI)

The effectiveness of hydroxyethylrutosides (HR) in clearing edema in the legs and in eliminating other signs of CVI has been conclusively shown in studies done on patients. Dosages of the bioflavonoids included tablets in strengths of 500 mg administered twice daily for a treatment period of 12 weeks, the results of double blind studies, on the whole, were positive.


Bruising Susceptibility

A double-blind study of 96 people with fragile capillaries found that a combination of the bioflavonoids diosmin and hesperidin decreased the tendency to bruise. Participants took 2 tablets daily of these bioflavonoids or placebo for 6 weeks, while researchers used a suction cup to measure their capillaries’ tendency to rupture and also looked for spontaneous bruising and other symptoms of fragile capillaries. Those individuals who received bioflavonoids had significantly greater improvements in both capillary strength and symptoms compared to those taking placebo. [Int Angiol. 1993;12: pp.69-72]

Two other studies from the 1960s found benefits with a combination of vitamin C and citrus bioflavonoids for decreasing bruising in collegiate athletes. In a single-blind study of 27 wrestlers, 71% of those taking placebo were injured, with bruises making up more than half their injuries; in contrast, only 38% of those taking the supplement were injured, none of whom sustained bruises. In a follow-up double-blind study of 40 football players, the treated group received fewer severe bruises than the group taking placebo.[Med Times. 1960;88: pp.313-316]


Varicose Veins

Bioflavonoids may be useful because of their reported antioxidant properties, their ability to increase the strength of the capillaries, and to regulate their permeability. Rutin, in particular, is often recommended for varicose veins.



Due to its antioxidant effect, quercetin can inhibit inflammatory processes mediated by “leukotrienes” (inflammatory agents a thousand times more powerful than histamines), hyaluronidase (collagen-destroying enzymes), and lysosomal enzymes (other promoters of localized inflammation).



Researchers reported that consuming dark chocolate and cocoa improves the function of blood vessels. In one study, consumption of cocoa in healthy volunteers, aged 18 to 77, resulted in significantly improved vascular responsiveness. The measure the researchers used looked at the “stiffness” of blood vessels. In patients whose blood vessels that are “stiff,” hypertension is common. The beneficial effect was most pronounced in patients over 50 years of age and was due to the high flavonoid (polyphenol) content of dark chocolate.

In a second study, after volunteers ate 100 grams (3.5 ounces) of dark chocolate vascular responsiveness was again significantly improved. Investigators postulate that it is the flavonoids in chocolate that causes vascular improvement. Dark chocolate contains more flavonoids than lighter chocolate – and adding milk to chocolate (milk chocolate) inhibits the absorption of flavonoids. Any benefit gained by eating chocolate may be limited to dark chocolate (and cocoa).

These short-term studies demonstrated an immediate benefit, but it remains to be proven if there will be a long-term benefits. Polyphenols are a broad class of phytochemical compounds, to which flavanols belong. [JAMA, August 27, 2003]



Quercetin is being used widely for sinus problems.


Chronic Inflammation

Clinical trials have not yet examined the effects of the bioflavonoid quercetin in the treatment of inflammation. However, several inflammation-promoting pathways are known to be inhibited by quercetin.


Blood Type A

Quercetin may be of value for cancer prevention for those with blood type A.


Blood Type AB

Quercetin may be of value for cancer prevention in those with blood type AB.


Organ Health  


Quercetin has been reported to improve symptoms of non-bacterial prostatitis and prostadynia. An uncontrolled study of 500 mg BID for at least two weeks significantly improved symptoms in 59% of men with chronic prostatitis. [JANA 1999;2: pp.36-9] A later double-blinded study improved symptoms in 67% of men.[Urology 1999; 54: pp.960-3]



An estimated 270 to 300 million people worldwide are infected with hepatitis C and the conventional treatments — interferon and ribavirin — can have significant side effects. A new drug targeting cellular proteins rather than viral proteins would be a valuable addition to the treatment arsenal, said Samuel French, an assistant professor of pathology and senior author of the study.

French and his team set out to identify the cellular factors involved in hepatitis C replication and, using mass spectrometry, found that heat shock proteins (HSPs) 40 and 70 were important for viral infection. HSP 70 was previously known to be involved, but HSP 40 was linked for the first time to hepatitis C infection, French said. They further showed that the natural compound Quercetin, which inhibits the synthesis of these proteins, significantly inhibits viral infection in tissue culture.

“This is an important finding because we can block these proteins with the idea of reducing the level of the virus in people and, ideally, completely eliminate it,” said French, who also is a researcher at UCLA’s Jonsson Comprehensive Cancer Center.

The study appeared in the most recent issue of the journal Hepatology – January 2010.

Since Quercetin has been shown to inhibit hepatitis C infection, French said, a Phase I clinical trial will be launched at UCLA to determine if the compound is safe and effective.

Quercetin is a plant-derived bioflavonoid, and is used by some people as a nutritional supplement.



Quercetin appears to be important in the prevention of asthma attacks. It has been shown to inhibit histamine release from mast cells and basophils when stimulated by antigens (triggers). In addition, quercetin has both a vitamin C-sparing effect and a direct stabilizing effect on membranes, including mast cells. It is also an antioxidant. Other flavones also inhibit histamine release, but to a lesser degree.


Concern Over Wrinkled Skin

Dark chocolate rich in flavonoids — plant-based antioxidants — appears to protect against skin cancer and promote healthy skin, a study by German researchers found. The study involved 24 women who added hot cocoa to their breakfasts daily for about three months. Half received cocoa that contained 329 milligrams of flavanols while the rest received a placebo cocoa that contained only 27 mg of flavanols per serving.

At the end of the study results showed that women who drank the flavonoid-rich cocoa:



The flavonoid quercetin inhibits the manufacture and release of histamine and other allergic compounds involved in allergies. This suggests an as yet unproven preventative effect in managing hives. Some types of hives will respond, while others will not.


Menorrhagia (Heavy Periods)

Capillary fragility is believed to play a role in many cases of menorrhagia. Supplementation with vitamin C and bioflavonoids has been shown to reduce menorrhagia. As vitamin C is known to significantly increase iron absorption, its therapeutic effect could also be due to enhanced iron absorption.



Possible Pregnancy-Related Issues

Quercetin inhibits conversion of vitamin A to retinoic acid. Retinoic acid is needed to help control gene expression in unborn babies. “It’s possible that a diet rich in quercetin during pregnancy may upset retinoic acid production, and lead to incorrect development and birth defects,” Dr. Kitson says. “It has recently been found that some baby boys born to exclusively-vegetarian mothers (some vegetarian diets are high in naturally occurring quercetin) have urogenital abnormalities.”

However, there is currently no direct evidence indicating that quercetin causes chromosomal changes in the fetus. As a maximum safe dose for pregnant women or nursing mothers has not been established, a cautious recommendation would be that high doses of quercetin be avoided during the early part of pregnancy until further research is done.


May do some good
Likely to help
Highly recommended
May have adverse consequences
Reasonably likely to cause problems


Vitamin C

Also known as ascorbic acid, Vitamin C is a water-soluble antioxidant vitamin essential to the body's health. When bound to other nutrients, for example calcium, it would be referred to as "calcium ascorbate". As an antioxidant, it inhibits the formation of nitrosamines (a suspected carcinogen). Vitamin C is important for maintenance of bones, teeth, collagen and blood vessels (capillaries), enhances iron absorption and red blood cell formation, helps in the utilization of carbohydrates and synthesis of fats and proteins, aids in fighting bacterial infections, and interacts with other nutrients. It is present in citrus fruits, tomatoes, berries, potatoes and fresh, green leafy vegetables.


The primary protein within white fibers of connective tissue and the organic substance found in tendons, ligaments, cartilage, skin, teeth and bone.


High blood pressure. Hypertension increases the risk of heart attack, stroke, and kidney failure because it adds to the workload of the heart, causing it to enlarge and, over time, to weaken; in addition, it may damage the walls of the arteries.


Vitamin P. Any of a group of colored flavones (crystalline compounds) found next to the peel in many fruits. Essential for the stability and absorption of ascorbic acid.


A chemical in the body tissues, produced by the breakdown of histidine. It is released in allergic reactions and causes widening of capillaries, decreased blood pressure, increased release of gastric juice, fluid leakage forming itchy skin and hives, and tightening of smooth muscles of the bronchial tube and uterus.


Any of the smallest blood vessels connecting arterioles with venules and forming networks throughout the body.


A chemical compound that slows or prevents oxygen from reacting with other compounds. Some antioxidants have been shown to have cancer-protecting potential because they neutralize free radicals. Examples include vitamins C and E, alpha lipoic acid, beta carotene, the minerals selenium, zinc, and germanium, superoxide dismutase (SOD), coenzyme Q10, catalase, and some amino acids, like cystiene. Other nutrient sources include grape seed extract, curcumin, gingko, green tea, olive leaf, policosanol and pycnogenol.


Reducing inflammation by acting on body mechanisms, without directly acting on the cause of inflammation, e.g., glucocorticoids, aspirin.


(mg): 1/1,000 of a gram by weight.


Three times a day.

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.