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Bioflavonoids are the colored part of vegetables, fruits, flowers, herbs, and grains. Research has shown that bioflavonoids may have anti-inflammatory, anti-allergic, antiviral, and anti-cancer properties. They are not considered true vitamins as it has not been demonstrated that they are essential for for human functioning.

What are the functions of bioflavonoids?


Therapeutic uses

Bioflavoniods are used extensively in athletic injuries because they relieve pain, bumps and bruises. They also reduce pain located in the legs or across the back and lessen symptoms associated with prolonged bleeding and low serum calcium.

When taken with vitamin C, they reduce the symptoms of oral herpes.

Quercetin (a bioflavonoid) has been used to block an enzyme that leads to accumulation ofsorbitol, which has been linked to nerve, eye, and kidney damage in those with diabetes.

Quercetin is considered a phytoestrogen (a plant substance which acts in a similar way to estrogen). Some phytoestrogens are believed also to have antiestrogenic effects that might lead to reduced risks of certain cancers. Quercetin was found to have this antiestrogenic activity, by inhibiting breast cancer cells in a test tube.

It may help treat or even prevent prostate cancer by blocking male hormones that encourage the growth of prostate cancer cells, according to preliminary laboratory research at the Mayo Clinic. In another study, men with an inflamed prostate (prostatitis) reported reduced urinary symptoms when they took quercetin supplements.

Food sources of bioflavonoids

Bioflavonoids are found in fruits and vegetables. Quercetin, for example, can be found in onions, apples, raspberries, green tea, red grapes, citrus fruit, cherries, broccoli, peppers, buckwheat, and black currants. Smaller amounts are found in leafy green vegetables and beans.


Bioflavonoids work to enhance vitamin C and should be taken as a part of a vitamin C supplement.

Special notes

No clear toxicity has been identified, however there are some early findings associated with large dose supplementation of some forms of bioflavonoids. Large doses can cause cancer in animals and quercetin has been shown to cause chromosomal mutations in certain bacteria in test tube studies.

Although the significance of this finding for humans is not clear, some health professionals are concerned about the possibility that birth defects could occur in the offspring of people supplementing with quercetin at the time of conception or during pregnancy.

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Balch, J,F. & Balch, P,A., 1990. Prescription for Nutritional Healing. Avery Publishing Group Inc.

Bland, J. 1996, Contemporary Nutrition. J & B Associates.

Holden, S., Hudson, K., Tilman, J. & D. Wolf, 2003, The Ultimate Guide to Health from Nature. Asrolog Publication.

Pressman, A. and S. Buff, 2000, The Complete Idiot's Guide to Vitamins and Minerals. (2nd Ed.) Alpha Books.

Soothill, R. 1996, The Choice Guide to Vitamins and Minerals. A Choice Book Publication.

Sullivan, K. 2002, Vitamins and Minerals: A Practical Approach to a Health Diet and Safe Supplementation. Harper Collins.

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Bioflavonoids were discovered by Albert Szent-Györgyi, in the 1930s. Szent-Györgyi won a Nobel Prize in medicine for his work with vitamin C. He found that when combined with vitamin C in his animal studies, a substance in the rinds of citrus fruits, which he named citrin, helped strengthen the small blood vessels.

When he traced the active ingredients in citrin, Szent-Györgyi discovered a group of substances that he named vitamin P. They were later called bioflavonoids. Quercetin is an example of a bioflavonoid. The human body cannot produce bioflavonoids, they must be supplied in the diet.


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